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  • how to run this qt script? (newbie question)

    - by GB_J
    I have a qt script(barchart.qs) that creates a graph for me. I don't know how i can incorporate(ie show the graph) in my qt mainwindow. Can some one please help me look at the code and what its outputs are? I tried engine.evaluate, but i do not know what is the QScriptValue i'm getting in return. Thanks sooo much. This is the script: BarChart.prototype = new QWidget; BarChart.prototype.suffix = ""; function BarChart(parent) { QWidget.call(this, parent); } // find the maximum value and widest (pixel-wise) label and suffix BarChart.prototype.showEvent = function(event) { var fm = new QFontMetrics(this); this.margin = 20; this.titleHeight = fm.height(); this.barHeight = 1.5 * fm.height(); this.barSpacing = 0.6 * fm.height(); this.maxValue = this.suffixWidth = this.labelWidth = 0; var count = 0; for (d in this.data) { this.labelWidth = Math.max(this.labelWidth, fm.width(d)); this.maxValue = Math.max(this.maxValue, this.data[d]); this.suffixWidth = Math.max(this.suffixWidth, fm.width(String(this.data[d]) + " " + this.suffix)); count++; } this.startHue = 15; this.hueDelta = 360 / count; this.size = new QSize(640, this.titleHeight + 2 * this.margin + (this.barHeight + this.barSpacing) * count); } BarChart.prototype.paintEvent = function(event) { var p = new QPainter; p.begin(this); // background and title p.fillRect(this.rect, new QBrush(new QColor(255, 255, 255))); p.drawText(0, 0, this.width, this.margin + this.titleHeight, Qt.AlignCenter, this.windowTitle, 0); var ofs = this.labelWidth + this.margin; var ww = this.width - this.suffixWidth - ofs - 2 * this.margin; var hue = this.startHue; var y = 0; p.translate(this.margin, this.titleHeight + 1.5 * this.margin); for (d in this.data) { // label on the left side p.setPen(new QColor(Qt.black)); p.drawText(0, y, this.labelWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignRight, d, 0); // the colored bar var gradient = new QLinearGradient(new QPoint(ofs, y), new QPoint(ofs, y + this.barHeight)); gradient.setColorAt(0, QColor.fromHsv(hue, 255, 240)); gradient.setColorAt(1, QColor.fromHsv(hue, 255, 92)); p.setBrush(new QBrush(gradient)); p.setPen(new QColor(96, 96, 96)); var bw = this.data[d] * ww / this.maxValue; p.drawRect(ofs, y, bw, this.barHeight); // extra text at the end of the bar var text = new String(this.data[d] + " " + this.suffix); p.setPen(new QColor(Qt.black)); p.drawText(ofs + bw + this.margin/2, y, this.suffixWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignLeft, text, 0); // for the next bar y += (this.barHeight + this.barSpacing); hue += this.hueDelta; if (hue >= 360) hue -= 360; } p.end(); } BarChart.prototype.wheelEvent = function(event) { this.startHue += event.delta() / 8 / 5; if (this.startHue = 360) this.startHue -= 360; if (this.startHue < 0) this.startHue += 360; this.update(); event.ignore(); } BarChart.prototype.mousePressEvent = function(event) { var fname = QFileDialog.getSaveFileName(this, "Save", ".", "*.png", 0, 0); if (fname.length > 0) { var img = new QImage(this.size, QImage.Format_ARGB32_Premultiplied); this.render(img); img.save(new QFile(fname)); } } var chart = new BarChart; chart.windowTitle = "Monthly"; chart.suffix = "reports"; chart.data = { "September" : 45, "October" : 60, "November" : 56, "December" : 0 }; chart.show(); QCoreApplication.exec();

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  • Trouble with detecting gestures over ListView

    - by Andrew
    I have an Activity that contains a ViewFlipper. The ViewFlipper includes 2 layouts, both of which are essentially just ListViews. So the idea here is that I have two lists and to navigate from one to the other I would use a horizontal swipe. I have that working. However, what ever list item your finger is on when the swipe begins executing, that item will also be long-clicked. Here is the relevant code I have: public class MyActivity extends Activity implements OnItemClickListener, OnClickListener { private static final int SWIPE_MIN_DISTANCE = 120; private static final int SWIPE_MAX_OFF_PATH = 250; private static final int SWIPE_THRESHOLD_VELOCITY = 200; private GestureDetector mGestureDetector; View.OnTouchListener mGestureListener; class MyGestureDetector extends SimpleOnGestureListener { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { try { if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH) return false; // right to left swipe if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { if (mCurrentScreen != SCREEN_SECONDLIST) { mCurrentScreen = SCREEN_SECONDLIST; mFlipper.setInAnimation(inFromRightAnimation()); mFlipper.setOutAnimation(outToLeftAnimation()); mFlipper.showNext(); updateNavigationBar(); } } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { if (mCurrentScreen != SCREEN_FIRSTLIST) { mCurrentScreen = SCREEN_FIRSTLIST; mFlipper.setInAnimation(inFromLeftAnimation()); mFlipper.setOutAnimation(outToRightAnimation()); mFlipper.showPrevious(); updateNavigationBar(); } } } catch (Exception e) { // nothing } return true; } } @Override public boolean onTouchEvent(MotionEvent event) { if (mGestureDetector.onTouchEvent(event)) return true; else return false; } ViewFlipper mFlipper; private int mCurrentScreen = SCREEN_FIRSTLIST; private ListView mList1; private ListView mList2; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.layout_flipper); mFlipper = (ViewFlipper) findViewById(R.id.flipper); mGestureDetector = new GestureDetector(new MyGestureDetector()); mGestureListener = new View.OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { if (mGestureDetector.onTouchEvent(event)) { return true; } return false; } }; // set up List1 screen mList1List = (ListView)findViewById(R.id.list1); mList1List.setOnItemClickListener(this); mList1List.setOnTouchListener(mGestureListener); // set up List2 screen mList2List = (ListView)findViewById(R.id.list2); mList2List.setOnItemClickListener(this); mList2List.setOnTouchListener(mGestureListener); } … } If I change the "return true;" statement from the GestureDetector to "return false;", I do not get long-clicks. Unfortunately, I get regular clicks. Does anyone know how I can get around this?

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  • Why isn't my algorithm for find the biggest and smallest inputs working?

    - by Matt Ellen
    I have started a new job, and with it comes a new language: Ironpython. Thankfully a good language :D Before starting I got to grips with Python on the whole, but that was only a week's worth of learning. Now I'm writing actual code. I've been charged with writing an algorithm that finds the best input parameter to collect data with. The basic algorithm is (as I've been instructed): Set the input parameter to a good guess Start collecting data When data is available stop collecting find the highest point If the point before this (i.e. for the previous parameter value) was higher and the point before that was lower then we've found the max otherwise the input parameter is increased by the initial guess. goto 2 If the max is found then the min needs to be found. To do this the algorithm carries on increasing the input, but by 1/10 of the max, until the current point is greater than the previous point and the point before that is also greater. Once the min is found then the algorithm stops. Currently I have a simplified data generator outputting the sin of the input, so that I know that the min value should be PI and the max value should be PI/2 The main Python code looks like this (don't worry, this is just for my edification, I don't write real code like this): import sys sys.path.append(r"F:\Programming Source\C#\PythonHelp\PythonHelp\bin\Debug") import clr clr.AddReferenceToFile("PythonHelpClasses.dll") import PythonHelpClasses from PHCStruct import Helper from System import Math helper = Helper() def run(): b = PythonHelpClasses.Executor() a = PythonHelpClasses.HasAnEvent() b.Input = 0.0 helper.__init__() def AnEventHandler(e): b.Stop() h = helper h.lastLastVal, h.lastVal, h.currentVal = h.lastVal, h.currentVal, e.Number if h.lastLastVal < h.lastVal and h.currentVal < h.lastVal and h.NotPast90: h.NotPast90 = False h.bestInput = h.lastInput inputInc = 0.0 if h.NotPast90: inputInc = Math.PI/10.0 else: inputInc = h.bestInput/10.0 if h.lastLastVal > h.lastVal and h.currentVal > h.lastVal and h.NotPast180: h.NotPast180 = False if h.NotPast180: h.lastInput, b.Input = b.Input, b.Input + inputInc b.Start(a) else: print "Best input:", h.bestInput print "Last input:", h.lastInput b.Stop() a.AnEvent += AnEventHandler b.Start(a) PHCStruct.py: class Helper(): def __init__(self): self.currentVal = 0 self.lastVal = 0 self.lastLastVal = 0 self.NotPast90 = True self.NotPast180 = True self.bestInput = 0 self.lastInput = 0 PythonHelpClasses has two small classes I wrote in C# before I realised how to do it in Ironpython. Executor runs a delegate asynchronously while it's running member is true. The important code: public void Start(HasAnEvent hae) { running = true; RunDelegate r = new RunDelegate(hae.UpdateNumber); AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar = r.BeginInvoke(Input, ac, null); } public void Stop() { running = false; } public void UpdateDone(IAsyncResult ar) { RunDelegate r = (RunDelegate)((AsyncResult)ar).AsyncDelegate; r.EndInvoke(ar); if (running) { AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar2 = r.BeginInvoke(Input, ac, null); } } HasAnEvent has a function that generates the sin of its input and fires an event with that result as its argument. i.e.: public void UpdateNumber(double val) { AnEventArgs e = new AnEventArgs(Math.Sin(val)); System.Threading.Thread.Sleep(1000); if (null != AnEvent) { AnEvent(e); } } The sleep is in there just to slow things down a bit. The problem I am getting is that the algorithm is not coming up with the best input being PI/2 and the final input being PI, but I can't see why. Also the best and final inputs are different each time I run the programme. Can anyone see why? Also when the algorithm terminates the best and final inputs are printed to the screen multiple times, not just once. Can someone explain why?

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  • Detecting Acceleration in a car (iPhone Accelerometer)

    - by TheGazzardian
    Hello, I am working on an iPhone app where we are trying to calculate the acceleration of a moving car. Similar apps have accomplished this (Dynolicious), but the difference is that this app is designed to be used during general city driving, not on a drag strip. This leads us to one big concern that Dynolicious was luckily able to avoid: hills. Yes, hills. There are two important stages to this: calibration, and actual driving. Our initial run was simple and suffered the consequences. During the calibration stage, I took the average force on the phone, and during running, I just subtracted the average force from the current force to get the current acceleration this frame. The problem with this is that the typical car receives much more force than just the forward force - everything from turning to potholes was causing the values to go out of sync with what was really happening. The next run was to add the condition that the iPhone must be oriented in such a way that the screen was facing toward the back of the car. Using this method, I attempted to follow only force on the z-axis, but this obviously lead to problems unless the iPhone was oriented directly upright, because of gravity. Some trigonometry later, and I had managed to work gravity out of the equation, so that the car was actually being read very, very well by the iPhone. Until I hit a slope. As soon as the angle of the car changed, suddenly I was receiving accelerations and decelerations that didn't make sense, and we were once again going out of sync. Talking with someone a lot smarter than me at math lead to a solution that I have been trying to implement for longer than I would like to admit. It's steps are as follows: 1) During calibration, measure gravity as a vector instead of a size. Store that vector. 2) When the car initially moves forward, take the vector of motion and subtract gravity. Use this as the forward momentum. (Ignore, for now, the user cases where this will be difficult and let's concentrate on the math :) 3) From the forward vector and the gravity vector, construct a plane. 4) Whenever a force is received, project it onto said plane to get rid of sideways force/etc. 5) Then, use that force, the known magnitude of gravity, and the known direction of forward motion to essentially solve a triangle to get the forward vector. The problem that is causing the most difficulty in this new system is not step 5, which I have gotten to the point where all the numbers look as they should. The difficult part is actually the detection of the forward vector. I am selecting vectors whose magnitude exceeds gravity, and from there, averaging them and subtracting gravity. (I am doing some error checking to make sure that I am not using a force just because the iPhone accelerometer was off by a bit, which happens more frequently than I would like). But if I plot these vectors that I am using, they actually vary by an angle of about 20-30 degrees, which can lead to some strong inaccuracies. The end result is that the app is even more inaccurate now than before. So basically - all you math and iPhone brains out there - any glaring errors? Any potentially better solutions? Any experience that could be useful at all? Award: offering a bounty of $250 to the first answer that leads to a solution.

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  • Anything wrong with this function for comparing floats?

    - by Michael Borgwardt
    When my Floating-Point Guide was yesterday published on slashdot, I got a lot of flak for my suggested comparison function, which was indeed inadequate. So I finally did the sensible thing and wrote a test suite to see whether I could get them all to pass. Here is my result so far. And I wonder if this is really as good as one can get with a generic (i.e. not application specific) float comparison function, or whether I still missed some edge cases. import static org.junit.Assert.assertFalse; import static org.junit.Assert.assertTrue; import org.junit.Test; public class NearlyEqualsTest { public static boolean nearlyEqual(float a, float b) { final float epsilon = 0.000001f; final float absA = Math.abs(a); final float absB = Math.abs(b); final float diff = Math.abs(a-b); if (a*b==0) { // a or b or both are zero // relative error is not meaningful here return diff < Float.MIN_VALUE / epsilon; } else { // use relative error return diff / (absA+absB) < epsilon; } } /** Regular large numbers - generally not problematic */ @Test public void big() { assertTrue(nearlyEqual(1000000f, 1000001f)); assertTrue(nearlyEqual(1000001f, 1000000f)); assertFalse(nearlyEqual(10000f, 10001f)); assertFalse(nearlyEqual(10001f, 10000f)); } /** Negative large numbers */ @Test public void bigNeg() { assertTrue(nearlyEqual(-1000000f, -1000001f)); assertTrue(nearlyEqual(-1000001f, -1000000f)); assertFalse(nearlyEqual(-10000f, -10001f)); assertFalse(nearlyEqual(-10001f, -10000f)); } /** Numbers around 1 */ @Test public void mid() { assertTrue(nearlyEqual(1.0000001f, 1.0000002f)); assertTrue(nearlyEqual(1.0000002f, 1.0000001f)); assertFalse(nearlyEqual(1.0002f, 1.0001f)); assertFalse(nearlyEqual(1.0001f, 1.0002f)); } /** Numbers around -1 */ @Test public void midNeg() { assertTrue(nearlyEqual(-1.000001f, -1.000002f)); assertTrue(nearlyEqual(-1.000002f, -1.000001f)); assertFalse(nearlyEqual(-1.0001f, -1.0002f)); assertFalse(nearlyEqual(-1.0002f, -1.0001f)); } /** Numbers between 1 and 0 */ @Test public void small() { assertTrue(nearlyEqual(0.000000001000001f, 0.000000001000002f)); assertTrue(nearlyEqual(0.000000001000002f, 0.000000001000001f)); assertFalse(nearlyEqual(0.000000000001002f, 0.000000000001001f)); assertFalse(nearlyEqual(0.000000000001001f, 0.000000000001002f)); } /** Numbers between -1 and 0 */ @Test public void smallNeg() { assertTrue(nearlyEqual(-0.000000001000001f, -0.000000001000002f)); assertTrue(nearlyEqual(-0.000000001000002f, -0.000000001000001f)); assertFalse(nearlyEqual(-0.000000000001002f, -0.000000000001001f)); assertFalse(nearlyEqual(-0.000000000001001f, -0.000000000001002f)); } /** Comparisons involving zero */ @Test public void zero() { assertTrue(nearlyEqual(0.0f, 0.0f)); assertFalse(nearlyEqual(0.00000001f, 0.0f)); assertFalse(nearlyEqual(0.0f, 0.00000001f)); } /** Comparisons of numbers on opposite sides of 0 */ @Test public void opposite() { assertFalse(nearlyEqual(1.000000001f, -1.0f)); assertFalse(nearlyEqual(-1.0f, 1.000000001f)); assertFalse(nearlyEqual(-1.000000001f, 1.0f)); assertFalse(nearlyEqual(1.0f, -1.000000001f)); assertTrue(nearlyEqual(10000f*Float.MIN_VALUE, -10000f*Float.MIN_VALUE)); } /** * The really tricky part - comparisons of numbers * very close to zero. */ @Test public void ulp() { assertTrue(nearlyEqual(Float.MIN_VALUE, -Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, Float.MIN_VALUE)); assertTrue(nearlyEqual(Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, Float.MIN_VALUE)); assertFalse(nearlyEqual(Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(-Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, 0.0f)); assertFalse(nearlyEqual(0.0f, 1e20f*Float.MIN_VALUE)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, -1e20f*Float.MIN_VALUE)); } }

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  • ActionScript Gradient Banding Problem

    - by TheDarkIn1978
    i'm having a strange issue with banding between certain colors of a gradient. to create the gradient, i'm drawing evenly spaced circle wedges from the center to the border, and filling each circle wedge from a bitmap line gradient pixel in a loop. public class ColorWheel extends Sprite { private static const DEFAULT_RADIUS:Number = 100; private static const DEFAULT_BANDING_QUALITY:int = 3600; public function ColorWheel(nRadius:Number = DEFAULT_RADIUS) { init(nRadius); } public function init(nRadius:Number = DEFAULT_RADIUS):void { var nRadians : Number; var nColor : Number; var objMatrix : Matrix = new Matrix(); var nX : Number; var nY : Number; var previousX : Number = nRadius; var previousY : Number = 0; var leftToRightColors:Array = new Array(0xFF0000, 0xFFFF00, 0x00FF00, 0x00FFFF, 0x0000FF, 0xFF00FF); leftToRightColors.push(leftToRightColors[0]); var leftToRightAlphas:Array = new Array(); var leftToRightRatios:Array = new Array(); var leftToRightPartition:Number = 255 / (leftToRightColors.length - 1); //Push arrays for (var j:int = 0; j < leftToRightColors.length; j++) { leftToRightAlphas.push(1); leftToRightRatios.push(j * leftToRightPartition); } var leftToRightColorsMatrix:Matrix = new Matrix(); leftToRightColorsMatrix.createGradientBox(DEFAULT_BANDING_QUALITY, 1); //Produce a horizontal leftToRightLine sprite var leftToRightLine:Sprite = new Sprite(); leftToRightLine.graphics.lineStyle(1, 0, 1, false, LineScaleMode.NONE, CapsStyle.NONE); leftToRightLine.graphics.lineGradientStyle(GradientType.LINEAR, leftToRightColors, leftToRightAlphas, leftToRightRatios, leftToRightColorsMatrix); leftToRightLine.graphics.moveTo(0, 0); leftToRightLine.graphics.lineTo(DEFAULT_BANDING_QUALITY, 0); //Assign bitmapData to the leftToRightLine var leftToRightLineBitmapData:BitmapData = new BitmapData(leftToRightLine.width, leftToRightLine.height); leftToRightLineBitmapData.draw(leftToRightLine); for(var i:int = 1; i < (DEFAULT_BANDING_QUALITY + 1); i++) { // Convert the degree to radians. nRadians = i * (Math.PI / (DEFAULT_BANDING_QUALITY / 2)); // OR the individual color channels together. nColor = leftToRightLineBitmapData.getPixel(i-1, 0); // Calculate the coordinate in which the line should be drawn to. nX = nRadius * Math.cos(nRadians); nY = nRadius * Math.sin(nRadians); // Create a matrix for the wedges gradient color. objMatrix.createGradientBox(nRadius * 2, nRadius * 2, nRadians, -nRadius, -nRadius); graphics.beginGradientFill(GradientType.LINEAR, [nColor, nColor], [1, 1], [127, 255], objMatrix); graphics.moveTo( 0, 0 ); graphics.lineTo( previousX, previousY ); graphics.lineTo( nX, nY ); graphics.lineTo( 0, 0 ); graphics.endFill(); previousX = nX; previousY = nY; } } } i'm creating a circle with 3600 wedges, although it doesn't look like it based on the screen shot within the orange color that is produced from gradating from red to yellow numbers. adding a orange number between red and yellow doesn't help. but if i create the circle with only 360 wedges, the gradient banding is much more obvious. 3600 is probably overkill, and doesn't really add more detail over, say, making the circle of 1440 wedges, but i don't know any other way to slightly elevate this banding issue. any ideas how i can fix this, or what i'm doing wrong? could it be caused by the circleMatrix rotation?

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  • Java code optimization leads to numerical inaccuracies and errors

    - by rano
    I'm trying to implement a version of the Fuzzy C-Means algorithm in Java and I'm trying to do some optimization by computing just once everything that can be computed just once. This is an iterative algorithm and regarding the updating of a matrix, the clusters x pixels membership matrix U, this is the update rule I want to optimize: where the x are the element of a matrix X (pixels x features) and v belongs to the matrix V (clusters x features). And m is a parameter that ranges from 1.1 to infinity. The distance used is the euclidean norm. If I had to implement this formula in a banal way I'd do: for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < V.length; j++) { double num = D[i][j]; double sumTerms = 0; for(int k = 0; k < V.length; k++) { double thisDistance = D[i][k]; sumTerms += Math.pow(num / thisDistance, (1.0 / (m - 1.0))); } U[i][j] = (float) (1f / sumTerms); } } In this way some optimization is already done, I precomputed all the possible squared distances between X and V and stored them in a matrix D but that is not enough, since I'm cycling througn the elements of V two times resulting in two nested loops. Looking at the formula the numerator of the fraction is independent of the sum so I can compute numerator and denominator independently and the denominator can be computed just once for each pixel. So I came to a solution like this: int nClusters = V.length; double exp = (1.0 / (m - 1.0)); for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < nClusters; j++) { double distance = D[i][j]; double denominator = D[i][nClusters]; double numerator = Math.pow(distance, exp); U[i][j] = (float) (1f / (numerator * denominator)); } } Where I precomputed the denominator into an additional column of the matrix D while I was computing the distances: for (int i = 0; i < X.length; i++) { for (int j = 0; j < V.length; j++) { double sum = 0; for (int k = 0; k < nDims; k++) { final double d = X[i][k] - V[j][k]; sum += d * d; } D[i][j] = sum; D[i][B.length] += Math.pow(1 / D[i][j], exp); } } By doing so I encounter numerical differences between the 'banal' computation and the second one that leads to different numerical value in U (not in the first iterates but soon enough). I guess that the problem is that exponentiate very small numbers to high values (the elements of U can range from 0.0 to 1.0 and exp , for m = 1.1, is 10) leads to ver y small values, whereas by dividing the numerator and the denominator and THEN exponentiating the result seems to be better numerically. The problem is it involves much more operations. Am I doing something wrong? Is there a possible solution to get both the code optimized and numerically stable? Any suggestion or criticism will be appreciated.

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  • Can someone explain this color wheel code to me?

    - by user1869438
    I just started doing java and i need some help with understanding this code. I got it from a this website. This is supposed to be code for a color wheel but i don't really understand how it works, especially the final ints STEPS and SLICES. import java.awt.Color; import objectdraw.*; public class ColorWheel extends WindowController { private double brightness; private Text text; private FilledRect swatch; private Location center; private int size; private FilledRect brightnessOverlay; private static final int SLICES = 96; private static final int STEPS = 16; public void begin() { canvas.setBackground(Color.BLACK); brightness = 1.; size = Math.min(canvas.getWidth(), canvas.getHeight() - 20); center = new Location(canvas.getWidth() / 2, size / 2); for(int j = STEPS; j >= 1; j--) { int arcSize = size * j / STEPS; int x = center.getX() - arcSize / 2; int y = center.getY() - arcSize / 2; for(int i = 0; i < SLICES; i++) { Color c = Color.getHSBColor((float)i / SLICES, (float)j / STEPS, (float)brightness); new FilledArc(x, y, arcSize, arcSize, i * 360. / SLICES, 360. / SLICES + .5, c, canvas); } } swatch = new FilledRect(0, canvas.getHeight() - 20, canvas.getWidth(), 20, Color.BLACK, canvas); brightnessOverlay = new FilledRect(0, 0, canvas.getWidth(), canvas.getHeight() - 20, new Color(0, 0, 0, 0), canvas); text = new Text("", canvas.getWidth() / 2, canvas.getHeight() - 18, canvas); text.setAlignment(Text.CENTER, Text.TOP); text.setBold(true); } public void onMouseDrag(Location point) { brightness = (canvas.getHeight() - point.getY()) / (double)(canvas.getHeight()); if(brightness < 0) { brightness = 0; } else if(brightness > 1) { brightness = 1; } if(brightness < .5) { text.setColor(Color.WHITE); } else { text.setColor(Color.BLACK); } brightnessOverlay.setColor(new Color(0f, 0f, 0f, (float)(1 - brightness))); } public void onMouseMove(Location point) { double saturation = 2 * center.distanceTo(point) / size; if(saturation > 1) { text.setText(""); swatch.setColor(Color.BLACK); return; } double hue = -Math.atan2(point.getY() - center.getY(), point.getX() - center.getX()) / (2 * Math.PI); if(hue < 0) { hue += 1; } swatch.setColor(Color.getHSBColor((float)hue, (float)saturation, (float)brightness)); text.setText("Color.getHSBColor(" + Text.formatDecimal(hue, 2) + "f, " + Text.formatDecimal(saturation, 2) + "f, " + Text.formatDecimal(brightness, 2) + "f)"); } }

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  • Using my custom colormap in Java for images

    - by John
    Hi everyone! I've got a question concering a colormapping via index. I tried this code found on http://www.podgoretsky.pri.ee/ftp/Docs/Java/Tricks%20of%20the%20Java%20Programming%20Gurus/ch12.htm // Gradient.java // Imports import java.applet.Applet; import java.awt.; import java.awt.image.; public class Gradient extends Applet { final int colors = 32; final int width = 200; final int height = 200; Image img; public void init() { // Create the color map byte[] rbmap = new byte[colors]; byte[] gmap = new byte[colors]; for (int i = 0; i < colors; i++) gmap[i] = (byte)((i * 255) / (colors - 1)); // Create the color model int bits = (int)Math.ceil(Math.log(colors) / Math.log(2)); IndexColorModel model = new IndexColorModel(bits, colors, rbmap, gmap, rbmap); // Create the pixels int pixels[] = new int[width * height]; int index = 0; for (int y = 0; y < height; y++) for (int x = 0; x < width; x++) pixels[index++] = (x * colors) / width; // Create the image img = createImage(new MemoryImageSource(width, height, model, pixels, 0, width)); } public void paint(Graphics g) { g.drawImage(img, 0, 0, this); } } It worked great but I tried to load a custom image jpeg mapped on my own colormap but it didnt work right. I saw only a bunch of green and blue pixels drawn on a white background. My custom color map method here: public void inintByteArrays() { double[][] c = // basic color map { { 0.0000, 0.0000, 0.5625 }, { 0.0000, 0.0000, 0.6250 }, { 0.0000, 0.0000, 0.6875 }, { 0.0000, 0.0000, 0.6875 }, { 0.0000, 0.0000, 0.7500 }, { 0.0000, 0.0000, 0.8125 }, { 0.0000, 0.0000, 0.8750 }, { 0.0000, 0.0000, 0.9375 }, { 0.0000, 0.0000, 1.0000 }, { 0.0000, 0.0625, 1.0000 }, { 0.0000, 0.1250, 1.0000 }, { 0.0000, 0.1875, 1.0000 }, { 0.0000, 0.2500, 1.0000 }, { 0.0000, 0.3125, 1.0000 }, { 0.0000, 0.3750, 1.0000 }, { 0.0000, 0.4375, 1.0000 }, { 0.0000, 0.5000, 1.0000 }, { 0.0000, 0.5625, 1.0000 }, { 0.0000, 0.6250, 1.0000 }, { 0.0000, 0.6875, 1.0000 }, { 0.0000, 0.7500, 1.0000 }, { 0.0000, 0.8125, 1.0000 }, { 0.0000, 0.8750, 1.0000 }, { 0.0000, 0.9375, 1.0000 }, { 0.0000, 1.0000, 1.0000 }, { 0.0625, 1.0000, 0.9375 }, { 0.1250, 1.0000, 0.8750 }, { 0.1875, 1.0000, 0.8125 }, { 0.2500, 1.0000, 0.7500 }, { 0.3125, 1.0000, 0.6875 }, { 0.3750, 1.0000, 0.6250 }, { 0.4375, 1.0000, 0.5625 }, { 0.5000, 1.0000, 0.5000 }, { 0.5625, 1.0000, 0.4375 }, { 0.6250, 1.0000, 0.3750 }, { 0.6875, 1.0000, 0.3125 }, { 0.7500, 1.0000, 0.2500 }, { 0.8125, 1.0000, 0.1875 }, { 0.8750, 1.0000, 0.1250 }, { 0.9375, 1.0000, 0.0625 }, { 1.0000, 1.0000, 0.0000 }, { 1.0000, 0.9375, 0.0000 }, { 1.0000, 0.8750, 0.0000 }, { 1.0000, 0.8125, 0.0000 }, { 1.0000, 0.7500, 0.0000 }, { 1.0000, 0.6875, 0.0000 }, { 1.0000, 0.6250, 0.0000 }, { 1.0000, 0.5625, 0.0000 }, { 1.0000, 0.5000, 0.0000 }, { 1.0000, 0.4375, 0.0000 }, { 1.0000, 0.3750, 0.0000 }, { 1.0000, 0.3125, 0.0000 }, { 1.0000, 0.2500, 0.0000 }, { 1.0000, 0.1875, 0.0000 }, { 1.0000, 0.1250, 0.0000 }, { 1.0000, 0.0625, 0.0000 }, { 1.0000, 0.0000, 0.0000 }, { 0.9375, 0.0000, 0.0000 }, { 0.8750, 0.0000, 0.0000 }, { 0.8125, 0.0000, 0.0000 }, { 0.7500, 0.0000, 0.0000 }, { 0.6875, 0.0000, 0.0000 }, { 0.6250, 0.0000, 0.0000 }, { 0.5625, 0.0000, 0.0000 }, { 0.5000, 0.0000, 0.0000 } }; for (int i = 0; i < c.length; i++) { for (int j = 0; j < c[i].length; j++) { if (j == 0) r[i] = (byte) ((byte) c[i][j]*255); if (j == 1) g[i] = (byte) ((byte) c[i][j]*255); if (j == 2) b[i] = (byte) ((byte) c[i][j]*255); } } My question is how I can use my colormap for any image I want to load and map in the right way. Thank you very much! Greetings, protein1.

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  • JavaScript Browser Hacks

    Recently during one of my client side scripting classes, I was trying to show my students some basic examples of JavaScript as an introduction to the language.  My first basic example was to show an alert box using JavaScript via the address bar. The student’s reaction to my browser hack example really caught me off guard in a good way. After programming with a language for close to 10 years you start to lose the "Awe Cool!" effect that new learners of a language experience when writing code. New learns of JavaScript are the reason why I created this post. Please enjoy. Note: Place JavaScript in to address bar and then press the enter key. Example 1: JavaScript Alert box displaying My name: John Doe Javascript:alert('My name: \n John Doe') ; Example 2: JavaScript alert box displaying name entered by user. javascript:alert('My name: \n ' + prompt('Enter Name','Name')) ; Example 3: JavaScript alert box displaying name entered by user, and then displays the length of the name. javascript:var name= prompt('Enter Name','Name'); alert('My name: \n ' + name); alert(name.length); If you notice, the address bar will execute JavaScript on the current page loaded in the browser using the Document Object Model (DOM). Additionally, the address bar will allow multiple lines to be executed sequentially even though all of the code is contained within one line due to the fact that the JavaScript interpreter uses the “;” to indicate where a line of ends and a new one begins. After doing a little more research on the topic of JavaScript Browser Hacks I found a few other cool JavaScript hacks which I will list below. Example 4: Make any webpage editableSource: http://www.openjason.com/2008/09/02/browser-hack-make-any-web-page-editable/ javascript:document.body.contentEditable='true'; document.designMode='on'; void 0; Example 5: CHINESE DRAGON DANCING Source: http://nzeyi.wordpress.com/2009/06/01/dwrajaxjavascript-hacks-the-secrets-of-javascript-in-the-adress-bar/ javascript:R=0;x1=0.1;y1=0.05;x2=0.25;y2=0.24;x3=1.6; y3=0.24;x4=300;y4=200;x5=300;y5=200;DI=document.links; DIL=DI.length;A=function(){for(i=0;i-DIL;i++){DI[i].style. position='absolute';DI[i].style.left=Math.sin(R*x1+i*x2+x3)*x4+ x5;DI[i].style.top=Math.cos(R*y1+i*y2+y3)*y4+y5}R++;}; setInterval('A()',5);void(0); Example 6: Reveal content stored in password protected fields javascript:(function(){var s,F,j,f,i; s = “”; F = document.forms; for(j=0; j Example 7: Force user to close browser windowSource: http://forums.digitalpoint.com/showthread.php?t=767053 javascript:while(1){alert('Restart your brower to close this box!')} Learn more about JavaScript Browser Hacks.

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  • PHP PSR-0 + several namespaces in one file and autoload

    - by Nemoden
    I've been thinking for a while about defining several namespaces in one php file and so, having several classes inside this file. Suppose, I want to implement something like Doctrine\ORM\Query\Expr: Expr.php Expr |-- Andx.php |-- Base.php |-- Comparison.php |-- Composite.php |-- From.php |-- Func.php |-- GroupBy.php |-- Join.php |-- Literal.php |-- Math.php |-- OrderBy.php |-- Orx.php `-- Select.php It would be nice if I had all of this in one file - Expr.php: namespace Doctrine\ORM\Query; class Expr { // code } namespace Doctrine\ORM\Query\Expr; class Func { // code } // etc... What I'm thinking of is directories naming convention and, unlike PSR-0 having several classes and namespaces in one file. It's best explained by the code: ls Doctrine/orm/query Expr.php that's it - only Expr.php Since Expr.php is somewhat I call a "meta-namespace" for Expr\Func, it make sense to place all the classes inside Expr.php (as shown above). So, the vendor name is still starts with an uppercased letter (Doctrine) and the other parts of namespace start with lowercased letter. We can write an autoload so it would respect this notion: function load_class($class) { if (class_exists($class)) { return true; } $tokenized_path = explode(array("_", "\\"), DIRECTORY_SEPARATOR, $class); // array('Doctrine', 'orm', 'query', 'Expr', 'Func'); // ^^^^ // first, we are looking for first uppercased namespace part // and if it's not last (not the class name), we use it as a filename // and wiping away the rest to compose a path to a file we need to include if (FALSE !== ($meta_class_index = find_meta_class($tokenized_path))) { $new_tokenized_path = array_slice($tokenized_path, 0, $meta_class_index); $path_to_class = implode(DIRECTORY_SEPARATOR, $new_tokenized_path); } else { // no meta class found $path_to_class = implode(DIRECTORY_SEPARATOR, $tokenized_path); } if (file_exists($path_to_class.'.php')) { require_once $path_to_class.'.php'; } return false; } Another reason to do so is to reduce a number of php files scattered among directories. Usually you check file existence before you require a file to fail gracefully: file_exists($path_to_class.'.php'); If you take a look at actual Doctrine\ORM\Query\Expr code, you'll see they use all of the "inner-classes", so you actually do: file_exists("/path/to/Doctrine/ORM/Query/Expr.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/AndX.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Base.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Comparison.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Composite.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/From.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Func.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/GroupBy.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Join.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Literal.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Math.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/OrderBy.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Orx.php"); file_exists("/path/to/Doctrine/ORM/Query/Expr/Select.php"); in your autoload which causes quite a few I/O reads. Isn't it too much to check on each user's hit? I'm just putting this on a discussion. I want to hear from another PHP programmers what do they think of it. And, of course, if you have a silver bullet addressing this problems I've designated here, please share. I also have been thinking if my vogue question fits here and according to the FAQ it seems like this question addresses "software architecture" problem slash proposal. I'm sorry if my scribble may seem a bit clunky :) Thanks.

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  • default xna 4.0 gametime don´t works well for 2D physics

    - by EusKoder
    I am developing a game using Visual Studio 2010 and XNA 4.0, after advancing to some extent with the project (a platform based 2d platformer msdn starter kit) I got to test it on different computers with different hardware (CPU, graphics, etc.) and I found that the speed of movement object of the game is quite different, I implemented the PSK physics msdn that are based on time, /// <summary> /// Updates the player's velocity and position based on input, gravity, etc. /// </summary> public void ApplyPhysics(GameTime gameTime) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; Vector2 previousPosition = Position; // Base velocity is a combination of horizontal movement control and // acceleration downward due to gravity. velocity.X += movement * MoveAcceleration * elapsed; velocity.Y = MathHelper.Clamp(velocity.Y + GravityAcceleration * elapsed, -MaxFallSpeed, MaxFallSpeed); velocity.Y = DoJump(velocity.Y, gameTime); // Apply pseudo-drag horizontally. if (IsOnGround) velocity.X *= GroundDragFactor; else velocity.X *= GroundDragFactor; //velocity.X *= AirDragFactor; // Prevent the player from running faster than his top speed. velocity.X = MathHelper.Clamp(velocity.X, -MaxMoveSpeed, MaxMoveSpeed); // Apply velocity. Position += velocity *elapsed; Position = new Vector2((float)Math.Round(Position.X), (float)Math.Round(Position.Y)); // If the player is now colliding with the level, separate them. HandleCollisions(gameTime); // If the collision stopped us from moving, reset the velocity to zero. if (Position.X == previousPosition.X) velocity.X = 0; if (Position.Y == previousPosition.Y) { velocity.Y = 0; jumpTime = 0.0f; } } tested eg with a PC (PC1) 2.13GHz Intel Core 2 6400 / ATI Radeon HD 4670 and another one: (pc2) 3.00GHz Intel Pentium D / Intel 82945G Express Chipset Family by displacement difference (moving x axis at supossed (position = velocity * gametime.ElapsedGameTime.TotalSeconds) constant velocity, for example) is 3 seconds in a total of 20 (example: moving pc1 player sprite 6000 pixels in the x-axis at 20 seconds and pc 2 runs the same distance in 17 ). Tested on a 3rd PC: i72700k / Gigabyte GTX 560 TI the results are even worse, after some time after starting the game gets like 3 times slower and showing the number of pixels in each frame moved in a debug window in the game (counting updatespersecond with counter variable for updates cuantity and gametime for counting a second show 63fps), it appears as if the number is always constant ( refreshments lose the Update method?). In this pc if I put the game in fullscreen during the course of the game, the effect of "go slow" is immediate and restore window mode sometimes yield returns to "normal" and sometimes not. Eventually I began to try a new project to test whether the movement is constant in different pc loading only one sprite and its position value in screen printing. Occur The same. I even tried moving a constant amount of pixels explicitly (position + = 5) and different speeds in different pc quantities of pixels moved in x time. I have the game loop as the default (fixedTimeStep=true;SynchronizeWithVerticalRetrace=true;). I've also tried turning off and creating another timestep as discussed in different post (eg http://gafferongames.com/game-physics/fix-your-timestep/ but i can´t achieve the desired result, move the same number of pixels in X seconds on different computers with windows. All pc used for tests use windows 7 enterprise pc1 == x86 the others are x64. The weirdest thing is that I find information about people describing the same problem and that I wear long nights of searches. Thanks for your help.

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  • Help finding time of collision

    - by WannaBe
    I am making a simple game right now and am struggling with collision response. My goal is to someday be able to turn it into a 2D platformer but I have a long way to go. I am currently making this in JavaScript and using the canvas element so (0,0) is in the top left and positive X is to the right and positive Y is down. I read a helpful post on StackExchange that got me started on this but I can't seem to get the algorithm 100% correct. How to deal with corner collisions in 2D? I can detect the collision fine but I can't seem to get the response right. The goal is to detect which side the player hit first since minimum displacement doesn't always work. The X response seems to work fine but the Y only works when I am far from the corners. Here is a picture showing what happens Here is the code var bx = box.x; var by = box.y; var bw = box.width; var bh = box.height; var boxCenterX = bx + (bw/2); var boxCenterY = by + (bh/2); var playerCenterX = player.x + player.xvel + (player.width/2); var playerCenterY = player.y + player.yvel + (player.height/2); //left = negative and right = positve, 0 = middle var distanceXin = playerCenterX - boxCenterX; var distanceYin = playerCenterY - boxCenterY; var distanceWidth = Math.abs(distanceXin); var distanceHeight = Math.abs(distanceYin); var halfWidths = (bw/2) + (player.width/2); var halfHeights = (bh/2) + (player.height/2); if(distanceWidth < halfWidths){ //xcollision if(distanceHeight < halfHeights){ //ycollision if(player.xvel == 0){ //adjust y if(distanceYin > 0){ //bottom player.y = by + bh; player.yvel = 0; }else{ player.y = by - player.height; player.yvel = 0; } }else if(player.yvel == 0){ //adjust x if(distanceXin > 0){ //right player.x = bx + bw; player.xvel = 0; }else{ //left player.x = bx - player.width; player.xvel = 0; } }else{ var yTime = distanceYin / player.yvel; var xTime = distanceXin / player.xvel; if(xTime < yTime){ //adjust the x it collided first if(distanceXin > 0){ //right player.x = bx + bw; player.xvel = 0; }else{ //left player.x = bx - player.width; player.xvel = 0; } }else{ //adjust the y it collided first if(distanceYin > 0){ //bottom player.y = by + bh; player.yvel = 0; }else{ player.y = by - player.height; player.yvel = 0; } } } } } And here is a JSFiddle if you would like to see the problem yourself. http://jsfiddle.net/dMumU/ To recreate this move the player to here And press up and left at the same time. The player will jump to the right for some reason. Any advice? I know I am close but I can't seem to get xTime and yTime to equal what I want every time.

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  • Converting openGl code to DirectX

    - by Fredrik Boston Westman
    First of all, this is kind of a follow up question on @byte56 excellent anwser on this question concerning picking algorithms. I'm trying to convert one of his code examples to directX 11 however I have run in to some problems ( I can pick but the picking is way off), and I wanted to make sure I had done it rigth before moving on and checking the rest of my code. I am not that familiar with openGl but I can imagine openGl has diffrent coordinations systems, and functions that alters how you must implement to code abit. This is his code example: public Ray GetPickRay() { int mouseX = Mouse.getX(); int mouseY = WORLD.Byte56Game.getHeight() - Mouse.getY(); float windowWidth = WORLD.Byte56Game.getWidth(); float windowHeight = WORLD.Byte56Game.getHeight(); //get the mouse position in screenSpace coords double screenSpaceX = ((float) mouseX / (windowWidth / 2) - 1.0f) * aspectRatio; double screenSpaceY = (1.0f - (float) mouseY / (windowHeight / 2)); double viewRatio = Math.tan(((float) Math.PI / (180.f/ViewAngle) / 2.00f))* zoomFactor; screenSpaceX = screenSpaceX * viewRatio; screenSpaceY = screenSpaceY * viewRatio; //Find the far and near camera spaces Vector4f cameraSpaceNear = new Vector4f((float) (screenSpaceX * NearPlane), (float) (screenSpaceY * NearPlane), (float) (-NearPlane), 1); Vector4f cameraSpaceFar = new Vector4f((float) (screenSpaceX * FarPlane), (float) (screenSpaceY * FarPlane), (float) (-FarPlane), 1); //Unproject the 2D window into 3D to see where in 3D we're actually clicking Matrix4f tmpView = Matrix4f(view); Matrix4f invView = (Matrix4f) tmpView.invert(); Vector4f worldSpaceNear = new Vector4f(); Matrix4f.transform(invView, cameraSpaceNear, worldSpaceNear); Vector4f worldSpaceFar = new Vector4f(); Matrix4f.transform(invView, cameraSpaceFar, worldSpaceFar); //calculate the ray position and direction Vector3f rayPosition = new Vector3f(worldSpaceNear.x, worldSpaceNear.y, worldSpaceNear.z); Vector3f rayDirection = new Vector3f(worldSpaceFar.x - worldSpaceNear.x, worldSpaceFar.y - worldSpaceNear.y, worldSpaceFar.z - worldSpaceNear.z); rayDirection.normalise(); return new Ray(rayPosition, rayDirection); } All rigths reserved to him of course This is my DirectX 11 code : void GraphicEngine::pickRayVector(float mouseX, float mouseY,XMVECTOR& pickRayInWorldSpacePos, XMVECTOR& pickRayInWorldSpaceDir) { float PRVecX, PRVecY; float nearPlane = 0.1f; float farPlane = 200.0f; floar viewAngle = 0.4 * 3.14; PRVecX = ((( 2.0f * mouseX) / ClientWidth ) - 1 ) * tan((viewAngle)/2); PRVecY = (1-(( 2.0f * mouseY) / ClientHeight)) * tan((viewAngle)/2); XMVECTOR cameraSpaceNear = XMVectorSet(PRVecX * nearPlane,PRVecY * nearPlane, -nearPlane, 1.0f); XMVECTOR cameraSpaceFar = XMVectorSet(PRVecX * farPlane,PRVecY * farPlane, -farPlane, 1.0f); // Transform 3D Ray from View space to 3D ray in World space XMMATRIX invMat; XMVECTOR matInvDeter; invMat = XMMatrixInverse(&matInvDeter, cam->getCameraView()); //Inverse of View Space matrix is World space matrix XMVECTOR worldSpaceNear = XMVector3TransformCoord(cameraSpaceNear, invMat); XMVECTOR worldSpaceFar = XMVector3TransformCoord(cameraSpaceFar, invMat); pickRayInWorldSpacePos = worldSpaceNear; pickRayInWorldSpaceDir = worldSpaceFar-worldSpaceNear; pickRayInWorldSpaceDir = XMVector3Normalize(pickRayInWorldSpaceDir); } A couple of notes: The mouse coordinates are already converted so that the top left corner of the client window would be (0,0) and the bottom rigth (800,600) ( or whatever resolution you would have) I hadn't used any far or near plane before, so i just made some arbitrary number up for them. To my understanding it shouldnt matter as long as the object you are trying to pick is in between the range of thoese numbers The viewAngle is the same angle that I used when setting the camera view with XMMatrixPerspectiveFovLH , I just hadn't made it a member variable of my Camera class yet. I removed the variable aspectRation and zoomFactor because I assumed that they where related to some specific function of his game. Now I'm not sure, but I think the problems lies either withing the mouse to viewspace conversion, maby that we use diffrent coordinations systems. Either that or how i transform the matrixes in the the end, because i know order is important when it comes to matrixes. Any help is appriciated! Thanks in advance. Edit: One more note, my code is in c++

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  • How to prepare for a programming competition? Graphs, Stacks, Trees, oh my! [closed]

    - by Simucal
    Last semester I attended ACM's (Association for Computing Machinery) bi-annual programming competition at a local University. My University sent 2 teams of 3 people and we competed amongst other schools in the mid-west. We got our butts kicked. You are given a packet with about 11 problems (1 problem per page) and you have 4 hours to solve as many as you can. They'll run your program you submit against a set of data and your output must match theirs exactly. In fact, the judging is automated for the most part. In any case.. I went there fairly confident in my programming skills and I left there feeling drained and weak. It was a terribly humbling experience. In 4 hours my team of 3 people completed only one of the problems. The top team completed 4 of them and took 1st place. The problems they asked were like no problems I have ever had to answer before. I later learned that in order to solve them some of them effectively you have to use graphs/graph algorithms, trees, stacks. Some of them were simply "greedy" algo's. My question is, how can I better prepare for this semesters programming competition so I don't leave there feeling like a complete moron? What tips do you have for me to be able to answer these problems that involve graphs, trees, various "well known" algorithms? How can I easily identify the algorithm we should implement for a given problem? I have yet to take Algorithm Design in school so I just feel a little out of my element. Here are some examples of the questions asked at the competitions: ACM Problem Sets Update: Just wanted to update this since the latest competition is over. My team placed 1st for our small region (about 6-7 universities with between 1-5 teams each school) and ~15th for the midwest! So, it is a marked improvement over last years performance for sure. We also had no graduate students on our team and after reviewing the rules we found out that many teams had several! So, that would be a pretty big advantage in my own opinion. Problems this semester ranged from about 1-2 "easy" problems (ie bit manipulation, string manipulation) to hard (graph problems involving fairly complex math and network flow problems). We were able to solve 4 problems in our 5 hours. Just wanted to thank everyone for the resources they provided here, we used them for our weekly team practices and it definitely helped! Some quick tips that I have that aren't suggested below: When you are seated at your computer before the competition starts, quickly type out various data structures that you might need that you won't have access to in your languages libraries. I typed out a Graph data-structure complete with floyd-warshall and dijkstra's algorithm before the competition began. We ended up using it in our 2nd problem that we solved and this is the main reason why we solved this problem before anyone else in the midwest. We had it ready to go from the beginning. Similarly, type out the code to read in a file since this will be required for every problem. Save this answer "template" someplace so you can quickly copy/paste it to your IDE at the beginning of each problem. There are no rules on programming anything before the competition starts so get any boilerplate code out the way. We found it useful to have one person who is on permanent whiteboard duty. This is usually the person who is best at math and at working out solutions to get a head start on future problems you will be doing. One person is on permanent programming duty. Your fastest/most skilled "programmer" (most familiar with the language). This will save debugging time also. The last person has several roles between assessing the packet of problems for the next "easiest" problem, helping the person on the whiteboard work out solutions and helping the person programming work out bugs/issues. This person needs to be flexible and be able to switch between roles easily.

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  • Physics like asteroides

    - by user2933016
    I try to make a ship that has the physic properties like asteroides. I have this for now(All in Java): Ship.class public class Ship { public static final float sMaxHealth = 0.1F; public static final float sMaxMoveVelocity = 5.0F; public static final float sMaxAngleVelocity = 20.0F; public static final float sRadius = 1.0F; public static final float sMoveDeceleration = 10.0F; public static final float sMoveAcceleration = 2.0F; public static final float sAngleDeceleration = 15.0F; public static final float sAngleAcceleration = 20.0F; private float mHealth; private float mXVelocity; private float mYVelocity; private float mAngleVelocity; private float mX; private float mY; private float mAngle; } (I let the getter and setter away for now) Controller code // Player input if(Gdx.input.isKeyPressed(Keys.UP)) { mPlayer.setXVelocity(mPlayer.getXVelocity() + (float) Math.cos(mPlayer.getAngle()) * Ship.sMoveAcceleration); mPlayer.setYVelocity(mPlayer.getYVelocity() + (float) Math.sin(mPlayer.getAngle()) * Ship.sMoveAcceleration); } if(Gdx.input.isKeyPressed(Keys.LEFT)) { mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() + Ship.sAngleAcceleration * pDeltaTime); } if(Gdx.input.isKeyPressed(Keys.RIGHT)) { mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() - Ship.sAngleAcceleration * pDeltaTime); } // X velocity if(mPlayer.getXVelocity() < 0) { if(-mPlayer.getXVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setXVelocity(-Ship.sMaxMoveVelocity); } mPlayer.setXVelocity(mPlayer.getXVelocity() + Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getXVelocity() > 0) { mPlayer.setXVelocity(0); } } else if(mPlayer.getXVelocity() > 0) { if(mPlayer.getXVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setXVelocity(Ship.sMaxMoveVelocity); } mPlayer.setXVelocity(mPlayer.getXVelocity() - Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getXVelocity() < 0) { mPlayer.setXVelocity(0); } } // Y velocity if(mPlayer.getYVelocity() < 0) { if(-mPlayer.getYVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setYVelocity(-Ship.sMaxMoveVelocity); } mPlayer.setYVelocity(mPlayer.getYVelocity() + Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getYVelocity() > 0) { mPlayer.setYVelocity(0); } } else if(mPlayer.getYVelocity() > 0) { if(mPlayer.getYVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setYVelocity(Ship.sMaxMoveVelocity); } mPlayer.setYVelocity(mPlayer.getYVelocity() - Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getYVelocity() < 0) { mPlayer.setYVelocity(0); } } // Angle velocity if(mPlayer.getAngleVelocity() < 0) { if(-mPlayer.getAngleVelocity() > Ship.sMaxAngleVelocity) { mPlayer.setAngleVelocity(-Ship.sMaxAngleVelocity); } mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() + Ship.sAngleDeceleration * pDeltaTime); if(mPlayer.getAngleVelocity() > 0) { mPlayer.setAngleVelocity(0); } } else if(mPlayer.getAngleVelocity() > 0) { if(mPlayer.getAngleVelocity() > Ship.sMaxAngleVelocity) { mPlayer.setAngleVelocity(Ship.sMaxAngleVelocity); } mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() - Ship.sAngleDeceleration * pDeltaTime); if(mPlayer.getAngleVelocity() < 0) { mPlayer.setAngleVelocity(0); } } mPlayer.setX(mPlayer.getX() + mPlayer.getXVelocity() * pDeltaTime); mPlayer.setY(mPlayer.getY() + mPlayer.getYVelocity() * pDeltaTime); mPlayer.setAngle(mPlayer.getAngle() + mPlayer.getAngleVelocity() * pDeltaTime); Why the ship does not behave like in asteroides ? What do I wrong?

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  • Wikipedia A* pathfinding algorithm takes a lot of time

    - by Vee
    I've successfully implemented A* pathfinding in C# but it is very slow, and I don't understand why. I even tried not sorting the openNodes list but it's still the same. The map is 80x80, and there are 10-11 nodes. I took the pseudocode from here Wikipedia And this is my implementation: public static List<PGNode> Pathfind(PGMap mMap, PGNode mStart, PGNode mEnd) { mMap.ClearNodes(); mMap.GetTile(mStart.X, mStart.Y).Value = 0; mMap.GetTile(mEnd.X, mEnd.Y).Value = 0; List<PGNode> openNodes = new List<PGNode>(); List<PGNode> closedNodes = new List<PGNode>(); List<PGNode> solutionNodes = new List<PGNode>(); mStart.G = 0; mStart.H = GetManhattanHeuristic(mStart, mEnd); solutionNodes.Add(mStart); solutionNodes.Add(mEnd); openNodes.Add(mStart); // 1) Add the starting square (or node) to the open list. while (openNodes.Count > 0) // 2) Repeat the following: { openNodes.Sort((p1, p2) => p1.F.CompareTo(p2.F)); PGNode current = openNodes[0]; // a) We refer to this as the current square.) if (current == mEnd) { while (current != null) { solutionNodes.Add(current); current = current.Parent; } return solutionNodes; } openNodes.Remove(current); closedNodes.Add(current); // b) Switch it to the closed list. List<PGNode> neighborNodes = current.GetNeighborNodes(); double cost = 0; bool isCostBetter = false; for (int i = 0; i < neighborNodes.Count; i++) { PGNode neighbor = neighborNodes[i]; cost = current.G + 10; isCostBetter = false; if (neighbor.Passable == false || closedNodes.Contains(neighbor)) continue; // If it is not walkable or if it is on the closed list, ignore it. if (openNodes.Contains(neighbor) == false) { openNodes.Add(neighbor); // If it isn’t on the open list, add it to the open list. isCostBetter = true; } else if (cost < neighbor.G) { isCostBetter = true; } if (isCostBetter) { neighbor.Parent = current; // Make the current square the parent of this square. neighbor.G = cost; neighbor.H = GetManhattanHeuristic(current, neighbor); } } } return null; } Here's the heuristic I'm using: private static double GetManhattanHeuristic(PGNode mStart, PGNode mEnd) { return Math.Abs(mStart.X - mEnd.X) + Math.Abs(mStart.Y - mEnd.Y); } What am I doing wrong? It's an entire day I keep looking at the same code.

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  • Basic collision direction detection on 2d objects

    - by Osso Buko
    I am trying to develop a platform game for Android by using ANdroid GL Engine (ANGLE). And I am having trouble with collision detection. I have two objects which is shaped as rectangular. And no change in rotation. Here is a scheme of attributes of objects. What i am trying to do is when objects collide they block each other's movement on that direction. Every object has 4 boolean (bTop, bBottom, bRight, bLeft). For example when bBottom is true object can't advance on that direction. I came up with a solution but it seems it only works on one dimensional. Bottom and top or right and left. public void collisionPlatform (MyObject a, MyObject b) { // first obj is player and second is a wall or a platform Vector p1 = a.mPosition; // p1 = middle point of first object Vector d1 = a.mPosition2; // width(mX) and height of first object Vector mSpeed1 = a.mSpeed; // speed vector of first object Vector p2 = b.mPosition; // p1 = middle point of second object Vector d2 = b.mPosition2; // width(mX) and height of second object Vector mSpeed2 = b.mSpeed; // speed vector of second object float xDist, yDist; // distant between middle of two object float width , height; // this is average of two objects measurements width=(width1+width2)/2 xDist=(p1.mX - p2.mX); // calculate distance // if positive first object is at the right yDist=(p1.mY - p2.mY); // if positive first object is below width = d1.mX + d2.mX; // average measurements calculate height = d1.mY + d2.mY; width/=2; height/=2; if (Math.abs(xDist) < width && Math.abs(yDist) < height) { // Two object is collided if(p1.mY>p2.mY) { // first object is below second one a.bTop = true; if(a.mSpeed.mY<0) a.mSpeed.mY=0; b.bBottom = true; if(b.mSpeed.mY>0) b.mSpeed.mY=0; } else { a.bBottom = true; if(a.mSpeed.mY>0) a.mSpeed.mY=0; b.bTop = true; if(b.mSpeed.mY<0) b.mSpeed.mY=0; } } As seen in my code it simply will not work. when object comes from right or left it doesn't work. I tried couple of ways other than this one but none worked. I am guessing right method will include mSpeed vector. But I have no idea how to do it. I really appreciate if you could help. Sorry for my bad english.

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  • Dynamically load and call delegates based on source data

    - by makerofthings7
    Assume I have a stream of records that need to have some computation. Records will have a combination of these functions run Sum, Aggregate, Sum over the last 90 seconds, or ignore. A data record looks like this: Date;Data;ID Question Assuming that ID is an int of some kind, and that int corresponds to a matrix of some delegates to run, how should I use C# to dynamically build that launch map? I'm sure this idea exists... it is used in Windows Forms which has many delegates/events, most of which will never actually be invoked in a real application. The sample below includes a few delegates I want to run (sum, count, and print) but I don't know how to make the quantity of delegates fire based on the source data. (say print the evens, and sum the odds in this sample) using System; using System.Threading; using System.Collections.Generic; internal static class TestThreadpool { delegate int TestDelegate(int parameter); private static void Main() { try { // this approach works is void is returned. //ThreadPool.QueueUserWorkItem(new WaitCallback(PrintOut), "Hello"); int c = 0; int w = 0; ThreadPool.GetMaxThreads(out w, out c); bool rrr =ThreadPool.SetMinThreads(w, c); Console.WriteLine(rrr); // perhaps the above needs time to set up6 Thread.Sleep(1000); DateTime ttt = DateTime.UtcNow; TestDelegate d = new TestDelegate(PrintOut); List<IAsyncResult> arDict = new List<IAsyncResult>(); int count = 1000000; for (int i = 0; i < count; i++) { IAsyncResult ar = d.BeginInvoke(i, new AsyncCallback(Callback), d); arDict.Add(ar); } for (int i = 0; i < count; i++) { int result = d.EndInvoke(arDict[i]); } // Give the callback time to execute - otherwise the app // may terminate before it is called //Thread.Sleep(1000); var res = DateTime.UtcNow - ttt; Console.WriteLine("Main program done----- Total time --> " + res.TotalMilliseconds); } catch (Exception e) { Console.WriteLine(e); } Console.ReadKey(true); } static int PrintOut(int parameter) { // Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " Delegate PRINTOUT waited and printed this:"+parameter); var tmp = parameter * parameter; return tmp; } static int Sum(int parameter) { Thread.Sleep(5000); // Pretend to do some math... maybe save a summary to disk on a separate thread return parameter; } static int Count(int parameter) { Thread.Sleep(5000); // Pretend to do some math... maybe save a summary to disk on a separate thread return parameter; } static void Callback(IAsyncResult ar) { TestDelegate d = (TestDelegate)ar.AsyncState; //Console.WriteLine("Callback is delayed and returned") ;//d.EndInvoke(ar)); } }

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  • WPF / C#: Transforming coordinates from an image control to the image source

    - by Gabriel
    I'm trying to learn WPF, so here's a simple question, I hope: I have a window that contains an Image element bound to a separate data object with user-configurable Stretch property <Image Name="imageCtrl" Source="{Binding MyImage}" Stretch="{Binding ImageStretch}" /> When the user moves the mouse over the image, I would like to determine the coordinates of the mouse with respect to the original image (before stretching/cropping that occurs when it is displayed in the control), and then do something with those coordinates (update the image). I know I can add an event-handler to the MouseMove event over the Image control, but I'm not sure how best to transform the coordinates: void imageCtrl_MouseMove(object sender, MouseEventArgs e) { Point locationInControl = e.GetPosition(imageCtrl); Point locationInImage = ??? updateImage(locationInImage); } Now I know I could compare the size of Source to the ActualSize of the control, and then switch on imageCtrl.Stretch to compute the scalars and offsets on X and Y, and do the transform myself. But WPF has all the information already, and this seems like functionality that might be built-in to the WPF libraries somewhere. So I'm wondering: is there a short and sweet solution? Or do I need to write this myself? EDIT I'm appending my current, not-so-short-and-sweet solution. Its not that bad, but I'd be somewhat suprised if WPF didn't provide this functionality automatically: Point ImgControlCoordsToPixelCoords(Point locInCtrl, double imgCtrlActualWidth, double imgCtrlActualHeight) { if (ImageStretch == Stretch.None) return locInCtrl; Size renderSize = new Size(imgCtrlActualWidth, imgCtrlActualHeight); Size sourceSize = bitmap.Size; double xZoom = renderSize.Width / sourceSize.Width; double yZoom = renderSize.Height / sourceSize.Height; if (ImageStretch == Stretch.Fill) return new Point(locInCtrl.X / xZoom, locInCtrl.Y / yZoom); double zoom; if (ImageStretch == Stretch.Uniform) zoom = Math.Min(xZoom, yZoom); else // (imageCtrl.Stretch == Stretch.UniformToFill) zoom = Math.Max(xZoom, yZoom); return new Point(locInCtrl.X / zoom, locInCtrl.Y / zoom); }

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  • WPF 4.0 Custom panel won't show dynamically added controls in VS 2010 Designer

    - by Matt Ruwe
    I have a custom panel control that I'm trying to dynamically add controls within. When I run the application the static and dynamically added controls show up perfectly, but the dynamic controls do not appear within the visual studio designer. Only the controls placed declaratively in the XAML appear. I'm currently adding the dynamic control in the CreateUIElementCollection override, but I've also tried this in the constructor without success. Public Class CustomPanel1 Inherits Panel Public Sub New() End Sub Protected Overrides Function MeasureOverride(ByVal availableSize As System.Windows.Size) As System.Windows.Size Dim returnValue As New Size(0, 0) For Each child As UIElement In Children child.Measure(availableSize) returnValue.Width = Math.Max(returnValue.Width, child.DesiredSize.Width) returnValue.Height = Math.Max(returnValue.Height, child.DesiredSize.Height) Next returnValue.Width = If(Double.IsPositiveInfinity(availableSize.Width), returnValue.Width, availableSize.Width) returnValue.Height = If(Double.IsPositiveInfinity(availableSize.Height), returnValue.Height, availableSize.Height) Return returnValue End Function Protected Overrides Function ArrangeOverride(ByVal finalSize As System.Windows.Size) As System.Windows.Size Dim currentHeight As Integer For Each child As UIElement In Children child.Arrange(New Rect(0, currentHeight, child.DesiredSize.Width, child.DesiredSize.Height)) currentHeight += child.DesiredSize.Height Next Return finalSize End Function Protected Overrides Function CreateUIElementCollection(ByVal logicalParent As System.Windows.FrameworkElement) As System.Windows.Controls.UIElementCollection Dim returnValue As UIElementCollection = MyBase.CreateUIElementCollection(logicalParent) returnValue.Add(New TextBlock With {.Text = "Hello, World!"}) Return returnValue End Function Protected Overrides Sub OnPropertyChanged(ByVal e As System.Windows.DependencyPropertyChangedEventArgs) MyBase.OnPropertyChanged(e) End Sub End Class And my usage of this custom panel <Window x:Class="MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:CustomPanel" Title="MainWindow" Height="364" Width="434"> <local:CustomPanel1> <CheckBox /> <RadioButton /> </local:CustomPanel1> </Window>

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  • jQuery $.ajax Not Working in IE8 but it works on FireFox & Chrome

    - by Sam3k
    I have the following ajax call which works perfectly in Firefox and Chrome but not IE: function getAJAXdates( startDate, numberOfNights, opts ) { var month = startDate.getMonth() + 1; var day = startDate.getDate(); var year = startDate.getFullYear(); var d = new Date(); var randNum = Math.floor(Math.random()*100000000); $.ajax({ type : "GET", dataType : "json", url : "/availability/ajax/bookings?rand="+randNum, cache : false, data : 'month='+month+'&day='+day+'&year='+year+'&nights='+numberOfNights, contentType : 'application/json; charset=utf8', success : function(data) { console.log('@data: '+data); insertCellData(data, opts, startDate); }, error:function(xhr, status, errorThrown) { console.log('@Error: '+errorThrown); console.log('@Status: '+status); console.log('@Status Text: '+xhr.statusText); } }); } I know for a fact that all the variables are passing the right content and $.ajax is indeed passing all the paramater/values. This is what I get on error: LOG: @Error: undefined LOG: @Status: parsererror LOG: @Status Text: OK I'm aware of the cache issue on IE and implemented a random paramater to clear it up. Finally these are the headers that are sent back from the backend: header('Content-Type: application/json; charset=utf8'); header("Cache-Control: no-cache"); header("Expires: 0"); header('Access-Control-Max-Age: 3628800'); header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE');

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  • TeX Font Mapping

    - by reprogrammer
    I am using a package written on top of XeLaTeX. This package uses fontspec to specify fonts for different parts of your text: latin, non-latin, math mode, ... The package comes with several sample files. I was able to xelatex most of them that depend on regular ttf or otf files. However, one of them tries to set the font of digits in math mode to some font, say "NonLatin Digits". But, the font doesn't seem to be a regular font. There are two files in the same directory called "nonlatindigits.map" and "nonlatindigits.tec". TECkit uses these mapping files to generate TeX fonts. However, for some reason it fails to create the files, and xelatex issues the following error message. kpathsea: Invalid fontname `NonLatin Digits', contains ' ' ! Font \zf@basefont="NonLatin Digits" at 10.0pt not loadable: Metric (TFM) file or installed font not found. The kpathsea program complains about the whitespace, but removing the whitespace does solve the problem with loading the TFM file. Any clues what I am doing wrong?

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  • FullCalendar and events: function

    - by Ernest
    I am trying to display my events from a MySQL database. I'm using the events function. My XML file being returned is pretty basic. I've looked at all of the FullCalendar questions and most of them talk about JSON and point to the documentation for JSON. I can't use JSON. I have to go XML. Can you tell me where I'm off. Here is a sample of what my xml looks like: Grow Your Business on the Web 2010-06-05T9:30 2010-06-05T12:30 O The whole file is prefaced with a tag and closed with a tag. My jquery is as follows: $(document).ready(function() { $('#calendar').fullCalendar({ height: 550, theme: true, header: { left: 'prev,next today', center: 'title', right: 'month,agendaWeek,agendaDay' }, editable: true, events: function(start, end, callback) { $.ajax({ url: 'ncludeFiles/sbdp-cal-xml.php', dataType: 'xml', data: { // our hypothetical feed requires UNIX timestamps start: Math.round(start.getTime() / 1000), end: Math.round(end.getTime() / 1000) }, success: function(doc) { var events = []; $(doc).find('event').each(function() { events.push({ title: $(this).attr('title'), start: $(this).attr('start'), end: $(this).attr('end'), className: $(this).attr('className'), url: $(this).attr('url') }); }); callback(events); } }); } }); }); I'd appreciate any help you could give me. Thanks!

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  • How to make Chrome redraw SVG dynamically added content?

    - by Adrian
    I've dynamacally added the circle elements to the svg displayed in a iFrame. Chrome isnt showing the new elements, not tried FF yet. Is there somekind of redraw/refresh I need to call? The first circle is actually in the svg document, the rest come from script. <iframe id="svgFrame" src="xmlfile1.svg" width="300" height="300"> <svg xmlns="http://www.w3.org/2000/svg" id="SVG1" width="200" height="200"> <circle cx="20" cy="20" r="5"/> <circle cx="165" cy="80" r="32"/> <circle cx="15" cy="38" r="32"/> <circle cx="140" cy="39" r="30"/> <circle cx="178" cy="32" r="22"/> ...etc <circle cx="166" cy="130" r="16"/> </svg> </iframe> The javascript which creates the elements: function RandomNumber(min, max) { var r; r = Math.floor(Math.random() * (max - min + 1)) + min; return r; } var svg = document.getElementById("svgFrame").contentDocument; for (var i = 0; i < 99; i++) { var n = svg.createElement("circle"); n.setAttribute("cx" , RandomNumber( 0 , 200) ); n.setAttribute("cy" , RandomNumber(0, 200) ); n.setAttribute("r" , RandomNumber(5, 35) ); svg.documentElement.appendChild(n); }

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