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  • When does depth testing happen?

    - by Utkarsh Sinha
    I'm working with 2D sprites - and I want to do 3D style depth testing with them. When writing a pixel shader for them, I get access to the semantic DEPTH0. Would writing to this value help? It seems it doesn't. Maybe it's done before the pixel shader step? Or is depth testing only done when drawing 3D things (I'm using SpriteBatch)? Any links/articles/topics to read/search for would be appreciated.

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  • HTML5 Canvas Game Timer

    - by zghyh
    How to create good timer for HTML5 Canvas games? I am using RequestAnimationFrame( http://paulirish.com/2011/requestanimationframe-for-smart-animating/ ) But object's move too fast. Something like my code is: http://pastebin.com/bSHCTMmq But if I press UP_ARROW player don't move one pixel, but move 5, 8, or 10 or more or less pixels. How to do if I press UP_ARROW player move 1 pixel? Thanks for help.

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  • Partial Shader Signatures HLSL D3D11 C++

    - by ThePhD
    I had been debugging a problem I was having in a single shader file with 2 functions in it. I'm using DirectX 11, vs_5_0 and ps_5_0. I have stripped it down to its basic components to understand what was going wrong with the shaders, because the different named components of the Pixel and Vertex shaders were swapping the data being input: void QuadVertex ( inout float4 position : SV_Position, inout float4 color : COLOR0, inout float2 tex : TEXCOORD0 ) { // ViewProject is a 4x4 matrix, // just included here to show the simple passthrough of the data position = mul(position, ViewProjection); } And a Pixel Shader: float4 QuadPixel ( float4 color : COLOR0, float2 tex : TEXCOORD0 ) : SV_Target0 { // Color is filled with position data and tex is // filled with color values from the Vertex Shader return color; } The ID3D11InputLayout and associated C++ code correctly compiles the shaders and sets them up with some simple primitive data: data[0].Position.x = 0.0f * 210; data[0].Position.y = 1.0f * 160; data[0].Position.z = 0.0f; data[1].Position.x = 0.0f * 210; data[1].Position.y = 0.0f * 160; data[1].Position.z = 0.0f; data[2].Position.x = 1.0f * 210; data[2].Position.y = 1.0f * 160; data[2].Position.z = 0.0f; data[0].Colour = Colors::Red; data[1].Colour = Colors::Red; data[2].Colour = Colors::Red; data[0].Texture = Vector2::Zero; data[1].Texture = Vector2::Zero; data[2].Texture = Vector2::Zero; When used with the shader, the float4 color always ended up with the position data, and the float2 tex always ended up with the color data. After a moment, I figured out that the shader's input and output signatures needed to be in the correct order and the correct format and be laid out in the exact order of the output from the Vertex Shader, regardless of the semantics: float4 QuadPixel ( float4 pos : SV_Position, float4 color : COLOR0, float2 tex : TEXCOORD0 ) : SV_Target0 { return color; } After finding this out, My question is: Why don't the semantics map the appropriate components when going from Vertex Shader to Pixel Shader? Is there any way that I can make it so certain semantics are always mapped to other semantics, or do I always have to follow the rigid Shader Signature (in this case, Position, Color, and Texture) ? As a side note for why I'm asking: I know that when using XNA, my shader signatures for functions could differ in position and even drop items from Vertex Shader to Pixel Shader function parameters, having only the COLOR0 and TEXCOORD0 components being used (and it would still match up correctly). However, I also know that XNA relied on DX9 (and maybe a little DX10) implementation, and that maybe this kind of flexibility no longer exists in DX11?

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  • Unique ways to use the Null Coalescing operator

    - by Atomiton
    I know the standard way of using the Null coalescing operator in C# is to set default values. string nobody = null; string somebody = "Bob Saget"; string anybody = ""; anybody = nobody ?? "Mr. T"; // returns Mr. T anybody = somebody ?? "Mr. T"; // returns "Bob Saget" But what else can ?? be used for? It doesn't seem as useful as the ternary operator, apart from being more concise and easier to read than: nobody = null; anybody = nobody == null ? "Bob Saget" : nobody; // returns Bob Saget So given that fewer even know about null coalescing operator... Have you used ?? for something else? Is ?? necessary, or should you just use the ternary operator (that most are familiar with)

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  • MapReduce results seem limited to 100?

    - by user1813867
    I'm playing around with Map Reduce in MongoDB and python and I've run into a strange limitation. I'm just trying to count the number of "book" records. It works when there are less than 100 records but when it goes over 100 records the count resets for some reason. Here is my MR code and some sample outputs: var M = function () { book = this.book; emit(book, {count : 1}); } var R = function (key, values) { var sum = 0; values.forEach(function(x) { sum += 1; }); var result = { count : sum }; return result; } MR output when record count is 99: {u'_id': u'superiors', u'value': {u'count': 99}} MR output when record count is 101: {u'_id': u'superiors', u'value': {u'count': 2.0}} Any ideas?

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  • How to Stich to Image objects in Java

    - by Imran
    Hi, I have a scenario in which i`m getting a number of tiles (e.g.12) from my mapping server. Now for buffering and offline functions I need to join them all back again so that we have to deal with 1 single image object instead of 12. I ve tried to do it without JAI my code is below. package imagemerge; import java.awt.*; import java.awt.image.*; import java.awt.event.*; public class ImageSticher extends WindowAdapter { Image tile1; Image tile2; Image result; ColorModel colorModel; int width,height,widthr,heightr; //int t1,t2; int t12[]; public ImageSticher() { } public ImageSticher (Image img1,Image img2,int w,int h) { tile1=img1; tile2=img2; width=w; height=h; colorModel=ColorModel.getRGBdefault(); } public Image horizontalStich() throws Exception { widthr=width*2; heightr=height; t12=new int[widthr * heightr]; int t1[]=new int[width*height]; PixelGrabber p1 =new PixelGrabber(tile1, 0, 0, width, height, t1, 0, width); p1.grabPixels(); int t2[]=new int[width*height]; PixelGrabber p2 =new PixelGrabber(tile2, 0, 0, width, height, t1, 0, width); p2.grabPixels(); int y, x, rp, rpi; int red1, red2, redr; int green1, green2, greenr; int blue1, blue2, bluer; int alpha1, alpha2, alphar; for(y=0;y<heightr;y++) { for(x=0;x<widthr;x++) { //System.out.println(x); rpi=y*widthr+x; // index of resulting pixel; rp=0; //initializing resulting pixel System.out.println(rpi); if(x<(widthr/2)) // x is less than width , copy first tile { //System.out.println("tile1="+x); blue1 = t1[rpi] & 0x00ff; // ERROR occurs here green1=(t1[rpi] >> 8) & 0x00ff; red1=(t1[rpi] >> 16) & 0x00ff; alpha1 = (t1[rpi] >> 24) & 0x00ff; redr = (int)(red1 * 1.0); // copying red band pixel into redresult,,,,1.0 is the alpha valye redr = (redr < 0)?(0):((redr>255)?(255):(redr)); greenr = (int)(green1 * 1.0); // redr = (int)(red1 * 1.0); // greenr = (greenr < 0)?(0):((greenr>255)?(255):(greenr)); bluer = (int)(blue1 * 1.0); bluer = (bluer < 0)?(0):((bluer>255)?(255):(bluer)); alphar = 255; //resulting pixel computed rp = (((((alphar << 8) + (redr & 0x0ff)) << 8) + (greenr & 0x0ff)) << 8) + (bluer & 0x0ff); } else // index is ahead of half way...copy second tile { blue2 = t2[rpi] & 0x00ff; // blue band bit of first tile green2=(t2[rpi] >> 8) & 0x00ff; red2=(t2[rpi] >> 16) & 0x00ff; alpha2 = (t2[rpi] >> 24) & 0x00ff; redr = (int)(red2 * 1.0); // copying red band pixel into redresult,,,,1.0 is the alpha valye redr = (redr < 0)?(0):((redr>255)?(255):(redr)); greenr = (int)(green2 * 1.0); // redr = (int)(red2 * 1.0); // greenr = (greenr < 0)?(0):((greenr>255)?(255):(greenr)); bluer = (int)(blue2 * 1.0); bluer = (bluer < 0)?(0):((bluer>255)?(255):(bluer)); alphar = 255; //resulting pixel computed rp = (((((alphar << 8) + (redr & 0x0ff)) << 8) + (greenr & 0x0ff)) << 8) + (bluer & 0x0ff); } t12[rpi] = rp; // copying resulting pixel in the result int array which will be converted to image } } MemoryImageSource mis; if (t12!=null) { mis = new MemoryImageSource(widthr, heightr, colorModel, t12, 0, widthr); result = Toolkit.getDefaultToolkit().createImage(mis); return result; } return null; } } now to check the my theory Im trying to join or stich two tiles horizontaly but im getting the error : java.lang.ArrayIndexOutOfBoundsException: 90000 at imagemerge.ImageSticher.horizontalStich(ImageSticher.java:69) at imageStream.ImageStream.getImage(ImageStream.java:75) at imageStream.ImageStream.main(ImageStream.java:28) is there some kind of limitation because when stiching two images of 300 x 300 horizontally it means the resulting image will be 600 x 300 ... that would make 180000 index size but its giving error at 90000, what am I doing wrong here

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  • Joel Spolsky Retires From Blogging in 3 Days

    - by andyleonard
    No it's not 1 Apr. Joel Spolsky ( Blog - @spolsky ) announced recently he is retiring from blogging 17 Mar 2010 . Reading Joel on Software always makes me think. Mr. Spolsky pioneered a writing style. Along the way he empowered developers, encouraging them to speak up about the manifold misconceptions of our trade. I will miss Mr. Spolsky's writings. I wish him well in all his endeavors. :{| Andy Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!...(read more)

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  • Open source engagement as a professional reference

    - by Martin
    if one commits his or her time to an open source project, he or she may be invest a substantial amount of time without getting paid. As much as altruism is appreciable, I wonder whether it "counts" as an activity which can be shown and is valued in job applications. If the company is worth your time and working power, which it should be in my honest opinion. So I wonder whether there is something like a common practice in open source projects for this matters. Say, something like Mr. Martin has been working on our project for five years and has contributed this and that,[...] I we wish him very best for his future. Mr. ChiefofProject I think this is a just concern. Do have experiences you can share?

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  • I want to trace the activity of my customize link sent via email or on chat to my custome

    - by anilkumble789
    I want to trace the activity of my customize link sent via email or on chat to my customer. Activity like : whether they opened the link or not? How much time they were on page? examples: I have decided to sent business proposal link to Mr.ABC and Mr.XYZ So, for ABC the link would be like : www.mycompany.com/proposal ....abc... So, for XYZ the link would be like : www.mycompany.com/proposal ....xyz... its like link analytic. How to go ahead with with it?

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  • What is the best option for reading Java property files?

    - by Mr Morgan
    Hello I have an application which uses a servlet to read an intialization parameter from web.xml for the location of a property file. The serlvet then creates an instance of a class which stores the location of the file for other programs to read as required. This class has appropriate get and set methods. But my question concerns access to the properties: should the physical property file be read by each program as at runtime or should the properties be stored in memory instead? The properties are not currently altered at runtime but this could change? I've seen various alternative approaches but am not sure which is best. Thanks Mr Morgan

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  • Getting the count of rows in a Java resultset

    - by Mr Morgan
    Hello Does anyone know a better way of getting the number of rows in a Java resultset returned from a MySQL database? I'm currently using this: public static int getResultSetRowCount(ResultSet resultSet) { int size = 0; try { resultSet.last(); size = resultSet.getRow(); resultSet.beforeFirst(); } catch(Exception ex) { return 0; } return size; } But am open to alternatives. The resultset returned is not going to be the total number of rows read from the database so I don;t think I can use SQL COUNT. Thanks Mr Morgan.

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  • Use of Java constructors in persistent entities

    - by Mr Morgan
    Hello I'm new to JPA and using persistence in Java anyway and I have two questions I can't quite work out: I have generated tags as: @JoinColumn(name = "UserName", referencedColumnName = "UserName") @ManyToOne(optional = false) private User userName; @JoinColumn(name = "DatasetNo", referencedColumnName = "DatasetNo") @ManyToOne(optional = false) private Dataset datasetNo; But in one of the constructors for the class, no reference is made to columns UserName or DatasetNo whereas all other columns in the class are referenced in the constructor. Can anyone tell me why this is? Both columns UserName and DatasetNo are 'foreign keys' on the entity Visualisation which corresponds to a database table of the same name. I can't quite work out the ORM. And when using entity classes, or POJO, is it better to have class variables like: private User userName; Where an instance of a class is specified or simply the key of that class instance like: private String userName; Thanks Mr Morgan.

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  • What is the significance of these different width, height and resolution parameters?

    - by ??????? ???????????
    An image with a pixel resolution of 640 x 480 has additional dimension and resolution parameters according to exiftool. I'm unsure what they mean. Why are the X / Y Resolution parameters the same?Should they not reflect the pixel dimensions of the image? What does Exif Image Size mean and how is it different from the pixel dimensions? What is the focal plane? Does it have any relation to the device used to capture this image? $ exiftool evil1.jpg | egrep 'Width|Height|Resolution' X Resolution : 180 Y Resolution : 180 Resolution Unit : inches Exif Image Width : 400 Exif Image Height : 300 Focal Plane X Resolution : 8114.285714 Focal Plane Y Resolution : 8114.285714 Focal Plane Resolution Unit : inches Image Width : 640 Image Height : 480 If needed, the original image can be obtained from: here=http://www.pythonchallenge.com/pc/return/evil1.jpg wget --user=huge --password=file $here

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  • image processing algorithm in MATLAB

    - by user261002
    I am trying to reconstruct an algorithm belong to this paper: Decomposition of biospeckle images in temporary spectral bands Here is an explanation of the algorithm: We recorded a sequence of N successive speckle images with a sampling frequency fs. In this way it was possible to observe how a pixel evolves through the N images. That evolution can be treated as a time series and can be processed in the following way: Each signal corresponding to the evolution of every pixel was used as input to a bank of filters. The intensity values were previously divided by their temporal mean value to minimize local differences in reflectivity or illumination of the object. The maximum frequency that can be adequately analyzed is determined by the sampling theorem and s half of sampling frequency fs. The latter is set by the CCD camera, the size of the image, and the frame grabber. The bank of filters is outlined in Fig. 1. In our case, ten 5° order Butterworth11 filters were used, but this number can be varied according to the required discrimination. The bank was implemented in a computer using MATLAB software. We chose the Butter-worth filter because, in addition to its simplicity, it is maximally flat. Other filters, an infinite impulse response, or a finite impulse response could be used. By means of this bank of filters, ten corresponding signals of each filter of each temporary pixel evolution were obtained as output. Average energy Eb in each signal was then calculated: where pb(n) is the intensity of the filtered pixel in the nth image for filter b divided by its mean value and N is the total number of images. In this way, en values of energy for each pixel were obtained, each of hem belonging to one of the frequency bands in Fig. 1. With these values it is possible to build ten images of the active object, each one of which shows how much energy of time-varying speckle there is in a certain frequency band. False color assignment to the gray levels in the results would help in discrimination. and here is my MATLAB code base on that : clear all for i=0:39 str = num2str(i); str1 = strcat(str,'.mat'); load(str1); D{i+1}=A; end new_max = max(max(A)); new_min = min(min(A)); for i=20:180 for j=20:140 ts = []; for k=1:40 ts = [ts D{k}(i,j)]; %%% kth image pixel i,j --- ts is time series end ts = double(ts); temp = mean(ts); ts = ts-temp; ts = ts/temp; N = 5; % filter order W = [0.00001 0.05;0.05 0.1;0.1 0.15;0.15 0.20;0.20 0.25;0.25 0.30;0.30 0.35;0.35 0.40;0.40 0.45;0.45 0.50]; N1 = 5; for ind = 1:10 Wn = W(ind,:); [B,A] = butter(N1,Wn); ts_f(ind,:) = filter(B,A,ts); end for ind=1:10 imag_test1{ind}(i,j) =sum((ts_f(ind,:)./mean(ts_f(ind,:))).^2); end end end for i=1:10 temp_imag = imag_test1{i}(:,:); x=isnan(temp_imag); temp_imag(x)=0; temp_imag=medfilt2(temp_imag); t_max = max(max(temp_imag)); t_min = min(min(temp_imag)); temp_imag = (temp_imag-t_min).*(double(new_max-new_min)/double(t_max-t_min))+double(new_min); imag_test2{i}(:,:) = temp_imag; end for i=1:10 A=imag_test2{i}(:,:); B=A/max(max(A)); B=histeq(B); figure,imshow(B) colorbar end but I am not getting the same result as paper. has anybody has aby idea why? or where I have gone wrong? Refrence Link to the paper

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  • Drawing outlines around organic shapes

    - by ThunderChunky_SF
    One thing that seems particularly easy to do in the Flash IDE but difficult to do with code is to outline an organic shape. In the IDE you can just use the inkbucket tool to draw a stroke around something. Using nothing but code it seems much trickier. One method I've seen is to add a glow filter to the shape in question and just mess with the strength. But what if i want to only show the outline? What I'd like to do is to collect all of the points that make up the edge of the shape and then just connect the dots. I've actually gotten so far as to collect all of the points with a quick and dirty edge detection script that I wrote. So now I have a Vector of all the points that makeup my shape. How do I connect them in the proper sequence so it actually looks like the original object? For anyone who is interested here is my edge detection script: // Create a new sprite which we'll use for our outline var sp:Sprite = new Sprite(); var radius:int = 50; sp.graphics.beginFill(0x00FF00, 1); sp.graphics.drawCircle(0, 0, radius); sp.graphics.endFill(); sp.x = stage.stageWidth / 2; sp.y = stage.stageHeight / 2; // Create a bitmap data object to draw our vector data var bmd:BitmapData = new BitmapData(sp.width, sp.height, true, 0); // Use a transform matrix to translate the drawn clip so that none of its // pixels reside in negative space. The draw method will only draw starting // at 0,0 var mat:Matrix = new Matrix(1, 0, 0, 1, radius, radius); bmd.draw(sp, mat); // Pass the bitmap data to an actual bitmap var bmp:Bitmap = new Bitmap(bmd); // Add the bitmap to the stage addChild(bmp); // Grab all of the pixel data from the bitmap data object var pixels:Vector.<uint> = bmd.getVector(bmd.rect); // Setup a vector to hold our stroke points var points:Vector.<Point> = new Vector.<Point>; // Loop through all of the pixels of the bitmap data object and // create a point instance for each pixel location that isn't // transparent. var l:int = pixels.length; for(var i:int = 0; i < l; ++i) { // Check to see if the pixel is transparent if(pixels[i] != 0) { var pt:Point; // Check to see if the pixel is on the first or last // row. We'll grab everything from these rows to close the outline if(i <= bmp.width || i >= (bmp.width * bmp.height) - bmp.width) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); continue; } // Check to see if the current pixel is on either extreme edge if(int(i % bmp.width) == 0 || int(i % bmp.width) == bmp.width - 1) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); continue; } // Check to see if the previous or next pixel are transparent, // if so save the current one. if(i > 0 && i < bmp.width * bmp.height) { if(pixels[i - 1] == 0 || pixels[i + 1] == 0) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); } } } }

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  • Fastest way to read data from a lot of ASCII files

    - by Alsenes
    Hi guys, for a college exercise that I've already submitted I needed to read a .txt file wich contained a lot of names of images(1 in each line). Then I needed to open each image as an ascii file, and read their data(images where in ppm format), and do a series of things with them. The things is, I noticed my program was taking 70% of the time in the reading the data from the file part, instead of in the other calculations that I was doing (finding number of repetitions of each pixel with a hash table, finding diferents pixels beetween 2 images etc..), which I found quite odd to say the least. This is how the ppm format looks like: P3 //This value can be ignored when reading the file, because all image will be correctly formatted 4 4 255 //This value can be also ignored, will be always 255. 0 0 0 0 0 0 0 0 0 15 0 15 0 0 0 0 15 7 0 0 0 0 0 0 0 0 0 0 0 0 0 15 7 0 0 0 15 0 15 0 0 0 0 0 0 0 0 0 This is how I was reading the data from the files: ifstream fdatos; fdatos.open(argv[1]); //Open file with the name of all the images const int size = 128; char file[size]; //Where I'll get the image name Image *img; while (fdatos >> file) { //While there's still images anmes left, continue ifstream fimagen; fimagen.open(file); //Open image file img = new Image(fimagen); //Create new image object with it's data file ……… //Rest of the calculations whith that image ……… delete img; //Delete image object after done fimagen.close(); //Close image file after done } fdatos.close(); And inside the image object read the data like this: const int tallafirma = 100; char firma[tallafirma]; fich_in >> std::setw(100) >> firma; // Read the P3 part, can be ignored int maxvalue, numpixels; fich_in >> height >> width >> maxvalue; // Read the next three values numpixels = height*width; datos = new Pixel[numpixels]; int r,g,b; //Don't need to be ints, max value is 256, so an unsigned char would be ok. for (int i=0; i<numpixels; i++) { fich_in >> r >> g >> b; datos[i] = Pixel( r, g ,b); } //This last part is the slow one, //I thing I should be able to read all this data in one single read //to buffer or something which would be stored in an array of unsigned chars, //and then I'd only need to to do: //buffer[0] -> //Pixel 1 - Red data //buffer[1] -> //Pixel 1 - Green data //buffer[2] -> //Pixel 1 - Blue data So, any Ideas? I think I can improve it quite a bit reading all to an array in one single call, I just don't know how that is done. Also, is it posible to know how many images will be in the "index file"? Is it posiible to know the number of lines a file has?(because there's one file name per line..) Thanks!!

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  • Are there any font rendering libraries for games development that support hinting?

    - by Richard Fabian
    I've used angel code's bitmap font generator quite a bit and though it's very good, I wondered if there would be a way of using the hinting information to provide a better readable result by using hinting to provide differing thickness based on size/pixel coverage. I imagine any solution would have to use the distance field tech presented in the valve paper on smoothing fonts while maintaining or reducing asset size. (http://www.gamedev.net/community/forums/topic.asp?topic_id=494612) but I haven't found any demos of it being used with hinting information turned on or included in the field gradients in any way. Another way of looking at this is whether there are any font bitmap generators that will output mipmaps that still maintain their readability in the face of pixel size. I think the lower mip levels would try to guarantee fill and space where it is necessary to maintain readability/topology over maintaining style/form (the point of hinting). In response to "Is there a reason you can't just render the size you want", the problem lies in the fact that font rasterisers currently don't render in 3D, and hinting information would be important in different amounts due to the pixel density being different along different axes, even differing in importance along the length of a string due to the size reducing over distance. For example, I only want horizontal hinting in a texture that is viewed from the side, and only really want vertical hinting in a font that is viewed from below or above. This isn't meant to be a renderer that tries to render a perfect outline as accurately as possible, as hinting distorts the reality of the font, instead this is meant to be a rendering solution for quite static scenes, but scenes that have 3D transformed and warped text layout. In this case the legibility is important, more important than the accuracy of representation of the polygon shape.

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  • How do graphics programmers deal with rendering vertices that don't change the image?

    - by canisrufus
    So, the title is a little awkward. I'll give some background, and then ask my question. Background: I work as a web GIS application developer, but in my spare time I've been playing with map rendering and improving data interchange formats. I work only in 2D space. One interesting issue I've encountered is that when you're rendering a polygon at a small scale (zoomed way out), many of the vertices are redundant. An extreme case would be that you have a polygon with 500,000 vertices that only takes up a single pixel. If you're sending this data to the browser, it would make sense to omit ~499,999 of those vertices. One way we achieve that is by rendering an image on a server and and sending it as a PNG: voila, it's a point. Sometimes, though, we want data sent to the browser where it can be rendered with SVG (or canvas, or webgl) so that it can be interactive. The problem: It turns out that, using modern geographic data sets, it's very easy to overload SVG's rendering abilities. In an effort to cope with those limitations, I'm trying to figure out how to visually losslessly reduce a data set for a given scale and map extent (and, if necessary, for a known map pixel width and height). I got a great reduction in data size just using the Douglas-Peucker algorithm, and I believe I was able to get it to keep the polygons true to within one pixel. Unfortunately, Douglas-Peucker doesn't preserve topology, so it changed how borders between polygons got rendered. I couldn't readily find other algorithms to try out and adapt to the purpose, but I don't have much CS/algorithm background and might not recognize them if I saw them.

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  • Orthographic unit translation mismatch on grid (e.g. 64 pixels translates incorrectly)

    - by Justin Van Horne
    I am looking for some insight into a small problem with unit translations on a grid. Setup 512x448 window 64x64 grid gl_Position = projection * world * position; projection is defined by ortho(-w/2.0f, w/2.0f, -h/2.0f, h/2.0f); This is a textbook orthogonal projection function. world is defined by a fixed camera position at (0, 0) position is defined by the sprite's position. Problem In the screenshot below (1:1 scaling) the grid spacing is 64x64 and I am drawing the unit at (64, 64), however the unit draws roughly ~10px in the wrong position. I've tried uniform window dimensions to prevent any distortion on the pixel size, but now I am a bit lost in the proper way in providing a 1:1 pixel-to-world-unit projection. Anyhow, here are some quick images to aide in the problem. I decided to super-impose a bunch of the sprites at what the engine believes is 64x offsets. When this seemed off place, I went about and did the base case of 1 unit. Which seemed to line up as expected. The yellow shows a 1px difference in the movement. Vertices It would appear that the vertices going into the vertex shader are correct. For example, in reference to the first image the data looks like this in the VBO: x y x y ---------------------------- tl | 0.0 24.0 64.0 24.0 bl | 0.0 0.0 -> 64.0 0.0 tr | 16.0 0.0 80.0 0.0 br | 16.0 24.0 80.0 24.0 With that said, all I am left to believe is that I am munging up my actual projection. So, I am looking for any insight into maintaining the 1:1 pixel-to-world-unit projection.

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  • How to Detect Sprites in a SpriteSheet?

    - by IAE
    I'm currently writing a Sprite Sheet Unpacker such as Alferds Spritesheet Unpacker. Now, before this is sent to gamedev, this isn't necessarily about games. I would like to know how to detect a sprite within a spriitesheet, or more abstactly, a shape inside of an image. Given this sprite sheet: I want to detect and extract all individual sprites. I've followed the algorithm detailed in Alferd's Blog Post which goes like: Determine predominant color and dub it the BackgroundColor Iterate over each pixel and check ColorAtXY == BackgroundColor If false, we've found a sprite. Keep going right until we find a BackgroundColor again, backtrack one, go down and repeat until a BackgroundColor is reached. Create a box from location to ending location. Repeat this until all sprites are boxed up. Combined overlapping boxes (or within a very short distance) The resulting non-overlapping boxes should contain the sprite. This implementation is fine, especially for small sprite sheets. However, I find the performance too poor for larger sprite sheets and I would like to know what algorithms or techniques can be leveraged to increase the finding of sprites. A second implementation I considered, but have not tested yet, is to find the first pixel, then use a backtracking algorithm to find every connected pixel. This should find a contiguous sprite (breaks down if the sprite is something like an explosion where particles are no longer part of the main sprite). The cool thing is that I can immediately remove a detected sprite from the sprite sheet. Any other suggestions?

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  • Collision with half semi-circle

    - by heitortsergent
    I am trying to port a game I made using Flash/AS3, to the Windows Phone using C#/XNA 4.0. You can see it here: http://goo.gl/gzFiE In the flash version I used a pixel-perfect collision between meteors (it's a rectangle, and usually rotated) that spawn outside the screen, and move towards the center, and a shield in the center of the screen(which is half of a semi-circle, also rotated by the player), which made the meteor bounce back in the opposite direction it came from, when they collided. My goal now is to make the meteors bounce in different angles, depending on the position it collides with the shield (much like Pong, hitting the borders causes a change in the ball's angle). So, these are the 3 options I thought of: -Pixel-perfect collision (microsoft has a sample(http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel_transformed)) , but then I wouldn't know how to change the meteor angle after the collision -3 BoundingCircle's to represent the half semi-circle shield, but then I would have to somehow move them as I rotate the shield. -Farseer Physics. I could make a shape composed of 3 lines, and use that as the collision object for the shield. Is there any other way besides those? Which would be the best way to do it(it's aimed towards mobile devices, so pixel-perfect is probably not a good choice)? Most of the time there's always a easier/better way than what we think of...

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  • Confusion with floats converted into ints during collision detection

    - by TheBroodian
    So in designing a 2D platformer, I decided that I should be using a Vector2 to track the world location of my world objects to retain some sub-pixel precision for slow-moving objects and other such subtle nuances, yet representing their bodies with Rectangles, because as far as collision detection and resolution is concerned, I don't need sub-pixel precision. I thought that the following line of thought would work smoothly... Vector2 wrldLocation; Point WorldLocation; Rectangle collisionRectangle; public void Update(GameTime gameTime) { Vector2 moveAmount = velocity * (float)gameTime.ElapsedGameTime.TotalSeconds wrldLocation += moveAmount; WorldLocation = new Point((int)wrldLocation.X, (int)wrldLocation.Y); collisionRectangle = new Rectangle(WorldLocation.X, WorldLocation.Y, genericWidth, genericHeight); } and I guess in theory it sort of works, until I try to use it in conjunction with my collision detection, which works by using Rectangle.Offset() to project where collisionRectangle would supposedly end up after applying moveAmount to it, and if a collision is found, finding the intersection and subtracting the difference between the two intersecting sides to the given moveAmount, which would theoretically give a corrected moveAmount to apply to the object's world location that would prevent it from passing through walls and such. The issue here is that Rectangle.Offset() only accepts ints, and so I'm not really receiving an accurate adjustment to moveAmount for a Vector2. If I leave out wrldLocation from my previous example, and just use WorldLocation to keep track of my object's location, everything works smoothly, but then obviously if my object is being given velocities less than 1 pixel per update, then the velocity value may as well be 0, which I feel further down the line I may regret. Does anybody have any suggestions about how I might go about resolving this?

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  • Best way to mask 2D sprites in XNA?

    - by electroflame
    I currently am trying to mask some sprites. Rather than explaining it in words, I've made up some example pictures: The area to mask (in white) Now, the red sprite that needs to be cropped. The final result. Now, I'm aware that in XNA you can do two things to accomplish this: Use the Stencil Buffer. Use a Pixel Shader. I have tried to do a pixel shader, which essentially did this: float4 main(float2 texCoord : TEXCOORD0) : COLOR0 { float4 tex = tex2D(BaseTexture, texCoord); float4 bitMask = tex2D(MaskTexture, texCoord); if (bitMask.a > 0) { return float4(tex.r, tex.g, tex.b, tex.a); } else { return float4(0, 0, 0, 0); } } This seems to crop the images (albeit, not correct once the image starts to move), but my problem is that the images are constantly moving (they aren't static), so this cropping needs to be dynamic. Is there a way I could alter the shader code to take into account it's position? Alternatively, I've read about using the Stencil Buffer, but most of the samples seem to hinge on using a rendertarget, which I really don't want to do. (I'm already using 3 or 4 for the rest of the game, and adding another one on top of it seems overkill) The only tutorial I've found that doesn't use Rendertargets is one from Shawn Hargreaves' blog over here. The issue with that one, though is that it's for XNA 3.1, and doesn't seem to translate well to XNA 4.0. It seems to me that the pixel shader is the way to go, but I'm unsure of how to get the positioning correct. I believe I would have to change my onscreen coordinates (something like 500, 500) to be between 0 and 1 for the shader coordinates. My only problem is trying to work out how to correctly use the transformed coordinates. Thanks in advance for any help!

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