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  • Number crunching algo for learning multithreading?

    - by Austin Henley
    I have never really implemented anything dealing with threads; my only experience with them is reading about them in my undergrad. So I want to change that by writing a program that does some number crunching, but splits it up into several threads. My first ideas for this hopefully simple multithreaded program were: Beal's Conjecture brute force based on my SO question. Bailey-Borwein-Plouffe formula for calculating Pi. Prime number brute force search As you can see I have an interest in math and thought it would be fun to incorporate it into this, rather than coding something such as a server which wouldn't be nearly as fun! But the 3 ideas don't seem very appealing and I have already done some work on them in the past so I was curious if anyone had any ideas in the same spirit as these 3 that I could implement?

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  • AI control for a ship with physics model

    - by Petteri Hietavirta
    I am looking for ideas how to implement following in 2D space. Unfortunately I don't know much about AI/path finding/autonomous control yet. Let's say this ship can move freely but it has mass and momentum. Also, external forces might affect it (explosions etc). The player can set a target for the ship at any time and it should reach that spot and stop. Without physics this would be simple, just point to the direction and go. But how to deal with existing momentum and then stopping on the spot? I don't want to modify ship's placement directly. edit: Just to make clear, the physics related math of the ship itself is not the problem.

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  • What DX level does my graphics card support? Does it go to 11?

    - by Daniel Moth
    Recently I run into a situation that I have run into quite a few times. Someone encounters a machine and the question arises: "Is there a DirectX 11 card in this machine?". Typically the reason you are interested in that is because cards with DirectX 11 drivers fully support DirectCompute (and by extension C++ AMP) for GPGPU programming. The driver specifically is WDDM (1.1 on Windows 7 and Windows 8 introduces WDDM 1.2 with cool new capabilities). There are many ways for figuring out if you have a DirectX11 card, so here are the approaches that you can use, with a bonus right at the end of the post. Run DxDiag WindowsKey + R, type DxDiag and hit Enter. That is the DirectX diagnostic tool, which unfortunately, only tells you on the "System" tab what is the highest version of DirectX installed on your machine. So if it reports DirectX 11, that doesn't mean you have a DX11 driver! The "Display" tab has a promising "DDI version" label, but unfortunately that doesn't seem to be accurate on the machines I've tested it with (or I may be misinterpreting its use). Either way, this tool is not the one you want for this purpose, although it is good for telling you the WDDM version among other things. Use the Microsoft hardware page There is a Microsoft Windows 7 compatibility center, that lists all hardware (tip: use the advanced search) and you could try and locate your device there… good luck. Use Wikipedia or the hardware vendor's website Use the Wikipedia page for the vendor cards, for both nvidia and amd. Often this information will also be in the specifications for the cards on the IHV site, but is is nice that wikipedia has a single page per vendor that you can search etc. There is a column in the tables for API support where you can see the DirectX version. Check if it is one of these recommended DX11 cards You may not have a DirectX 11 card and are interested in purchasing one. While I am in no position to make recommendations, I will list here some cards from two big IHVs that we know are DirectX 11 capable. Some AMD (aka ATI) cards Low end, inexpensive DX11 hardware: Radeon 5450, 5550, 6450, 6570 Mid range (decent perf, single precision): Radeon 5750, 5770, 6770, 6790 High end (capable of double precision): Radeon 5850, 5870, 6950, 6970 Single precision APUs: AMD E-Series APUs AMD A-Series APUs Some NVIDIA cards Low end, inexpensive DX11 hardware: GeForce GT430, GT 440, GT520, GTS 450 Quadro 400, 600 Mid-range (decent perf, single precision): GeForce GTX 460, GTX 550 Ti, GTX 560, GTX 560 Ti Quadro 2000 High end (capable of double precision): GeForce GTX 480, GTX 570, GTX 580, GTX 590, GTX 595 Quadro 4000, 5000, 6000 Tesla C2050, C2070, C2075 Get the DirectX SDK and run DirectX Caps Viewer Download and install the June 2010 DirectX SDK. As part of that you now have the DirectX Capabilities Viewer utility (find it in your start menu by searching for "DirectX Caps Viewer", the filename is DXCapsViewer.exe). It will list all your devices (emulated, and real hardware ones) under the first node. Expand the hardware entries and then expand again the Direct3D 11 folder. If you see D3D_FEATURE_LEVEL_11_ under that, then your card supports feature level 11 which means it supports DirectCompute and C++ AMP. In the following screenshot of one of my old laptops, the card only goes to feature level 10. Run a utility from the web that just tells you! Of course, writing some C++ AMP code that enumerates accelerators and lists the ones that are capable is trivial. However that requires that you have redistributed the runtime, so a more broadly applicable approach is to use the DX APIs directly to enumerate the DX11 capable cards. That is exactly what the development lead for C++ AMP has done and he describes and shares that utility at this post. Comments about this post by Daniel Moth welcome at the original blog.

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  • What DX level does my graphics card support? Does it go to 11?

    - by Daniel Moth
    Recently I run into a situation that I have run into quite a few times. Someone encounters a machine and the question arises: "Is there a DirectX 11 card in this machine?". Typically the reason you are interested in that is because cards with DirectX 11 drivers fully support DirectCompute (and by extension C++ AMP) for GPGPU programming. The driver specifically is WDDM (1.1 on Windows 7 and Windows 8 introduces WDDM 1.2 with cool new capabilities). There are many ways for figuring out if you have a DirectX11 card, so here are the approaches that you can use, with a bonus right at the end of the post. Run DxDiag WindowsKey + R, type DxDiag and hit Enter. That is the DirectX diagnostic tool, which unfortunately, only tells you on the "System" tab what is the highest version of DirectX installed on your machine. So if it reports DirectX 11, that doesn't mean you have a DX11 driver! The "Display" tab has a promising "DDI version" label, but unfortunately that doesn't seem to be accurate on the machines I've tested it with (or I may be misinterpreting its use). Either way, this tool is not the one you want for this purpose, although it is good for telling you the WDDM version among other things. Use the Microsoft hardware page There is a Microsoft Windows 7 compatibility center, that lists all hardware (tip: use the advanced search) and you could try and locate your device there… good luck. Use Wikipedia or the hardware vendor's website Use the Wikipedia page for the vendor cards, for both nvidia and amd. Often this information will also be in the specifications for the cards on the IHV site, but is is nice that wikipedia has a single page per vendor that you can search etc. There is a column in the tables for API support where you can see the DirectX version. Check if it is one of these recommended DX11 cards You may not have a DirectX 11 card and are interested in purchasing one. While I am in no position to make recommendations, I will list here some cards from two big IHVs that we know are DirectX 11 capable. Some AMD (aka ATI) cards Low end, inexpensive DX11 hardware: Radeon 5450, 5550, 6450, 6570 Mid range (decent perf, single precision): Radeon 5750, 5770, 6770, 6790 High end (capable of double precision): Radeon 5850, 5870, 6950, 6970 Single precision APUs: AMD E-Series APUs AMD A-Series APUs Some NVIDIA cards Low end, inexpensive DX11 hardware: GeForce GT430, GT 440, GT520, GTS 450 Quadro 400, 600 Mid-range (decent perf, single precision): GeForce GTX 460, GTX 550 Ti, GTX 560, GTX 560 Ti Quadro 2000 High end (capable of double precision): GeForce GTX 480, GTX 570, GTX 580, GTX 590, GTX 595 Quadro 4000, 5000, 6000 Tesla C2050, C2070, C2075 Get the DirectX SDK and run DirectX Caps Viewer Download and install the June 2010 DirectX SDK. As part of that you now have the DirectX Capabilities Viewer utility (find it in your start menu by searching for "DirectX Caps Viewer", the filename is DXCapsViewer.exe). It will list all your devices (emulated, and real hardware ones) under the first node. Expand the hardware entries and then expand again the Direct3D 11 folder. If you see D3D_FEATURE_LEVEL_11_ under that, then your card supports feature level 11 which means it supports DirectCompute and C++ AMP. In the following screenshot of one of my old laptops, the card only goes to feature level 10. Run a utility from the web that just tells you! Of course, writing some C++ AMP code that enumerates accelerators and lists the ones that are capable is trivial. However that requires that you have redistributed the runtime, so a more broadly applicable approach is to use the DX APIs directly to enumerate the DX11 capable cards. That is exactly what the development lead for C++ AMP has done and he describes and shares that utility at this post. Comments about this post by Daniel Moth welcome at the original blog.

    Read the article

  • How important is Discrete Mathematics for a Computer Scientist?

    - by mort
    As the title says, How important is Discrete Mathematics for a Computer Scientist? Background: I'm pursuing a Master's degree with a focus on fundamentals such as Algorithms, Complexity and Computability Theory and Programming Languages to get a good foundation for working in the field of Parallel Computing. Some more background: My university grants a lot of freedom in the choices of courses for my Master's degree. It's officially called "Software Engineering", but due to a the broad range of electives, a different focus is possible. Interestingly, none of the electives is a lecture in Math! I'm thinking about doing a course about Discrete Mathematics that would take half a semester to complete successfully, even if I can't use it for my degree. So with this question I'm trying to find out if the effort is justifiable.

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  • Can SpriteBatch be used to fill a polygon with a texture?

    - by can poyrazoglu
    I basically need to fill a texture into a polygon using the SpriteBatch. I've done some research but couldn't find anything useful except polygon triangulation method, which works well only with convex polygons (without diving into super math which is definitely not something I'm pretty good at). Are there any solutions for filling in a polygon in a basic way? I of course need something dynamic (I'll have a map editor that you can define polygons, and the game will render them (and collision detection will also use them but that's off topic), basically I can't accept solutions like "pre-calculated" bitmaps or anything like that. I need to draw a polygon with the segments provided, to the screen, using the SpriteBatch.

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  • Isometric Screen View to World View

    - by Sleepy Rhino
    I am having trouble working out the math to transform the screen coordinates to the Grid coordinates. The code below is how far I have got but it is totally wrong any help or resources to fix this issue would be great, had a complete mind block with this for some reason. private Point ScreenToIso(int mouseX, int mouseY) { int offsetX = WorldBuilder.STARTX; int offsetY = WorldBuilder.STARTY; Vector2 startV = new Vector2(offsetX, offsetY); int mapX = offsetX - mouseX; int mapY = offsetY - mouseY + (WorldBuilder.tileHeight / 2); mapY = -1 * (mapY / WorldBuilder.tileHeight); mapX = (mapX / WorldBuilder.tileHeight) + mapY; return new Point(mapX, mapY); }

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  • how to select categories for user generated content site?

    - by Frederik Creemers
    On the site I'm building, users can create tutorials. I want the users to be able to create tutorials on as many subjects as possible, but still have some preset categories. What's the best way to select these categories? The reason I don't just let users add keywords, and use these for categorization, is because users gain experience points in a certain subject when their tutorial is liked by someone, and in a similar way the Stack Exchange network does, create communities around these subjects. I will give visiters the possibility to suggest new categories. here are the categories that I'm thinking of at the moment: health gardening cooking technology science & math music visual art

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  • Continuous Movement of gun bullet

    - by Siddharth
    I was using box2d for the movement of the body. When I apply gravity (0,0) the bullet continuously move but when I change gravity to the earth the behavior was changed. I also try to apply continuous force to the bullet body but the behavior was not so good. So please provide any suggestion to continuously move bullet body in earth gravity. currentVelocity = bulletBody.getLinearVelocity(); if (currentVelocity.len() < speed|| currentVelocity.len() > speed + 0.25f) { velocityChange = Math.abs(speed - currentVelocity.len()); currentVelocity.set(currentVelocity.x* velocityChange, currentVelocity.y*velocityChange); bulletBody.applyLinearImpulse(currentVelocity,bulletBody.getWorldCenter()); } I apply above code for the continuous velocity of the body. And also I did not able to find any setGravityScale method in the library.

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  • Coding style advice? [closed]

    - by user1064918
    I'm a newly grad. I've got a lot of complaints from my supervisor at work during code-review sessions with regard to my coding style (Surprise!). I don't know if it's just him being cranky or my style is really that annoying to read. I come from the low-level language world (assembly, mostly), so I've been taught to use bitwise ops and all the cool tricks to do math whenever possible. I also have the habits of doing some other things that've been regarded as "too excessively dense to read". So I'm hoping to get some feedback from any experienced programmers! :) Also how should I justify between code performance and readability? Thanks!!

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  • xbox thumbstick used to rotate sprite, basic formula makes it "stick" or feel "sticky" at 90 degree intervals! how do get smooth rotation?

    - by Hugh
    Context: C#, XNA game I am using a very basic formula to calculate what angle my sprite (spaceship for example) should be facing based on the xbox controller thumbstick ie. you use the thumbstick to rotate the ship! in my main update method: shuttleAngle = (float) Math.Atan2(newGamePadState.ThumbSticks.Right.X, newGamePadState.ThumbSticks.Right.Y); in my main draw method: spriteBatch.Draw(shuttle, shuttleCoords, sourceRectangle, Color.White, shuttleAngle, origin, 1.0f, SpriteEffects.None, 1); as you can see its quite simple, i take the current radians from the thumbstick and store it in a float "shuttleAngle" and then use this as the rotation angle (in radians) arguement for drawing the shuttle. For some reason when i rotate the sprint it feels sticky at 0, 90, 180 and 270 degrees angles, it wants to settle at those angles. its not giving me a smooth and natural rotation like i would feel in a game that uses a similar mechanic. PS: my xbox controller is fine!

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  • Trying to detect collision between two polygons using Separating Axis Theorem

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • A*, Tile costs and heuristic; How to approach

    - by Kevin Toet
    I'm doing exercises in tile games and AI to improve my programming. I've written a highly unoptimised pathfinder that does the trick and a simple tile class. The first problem i ran into was that the heuristic was rounded to int's which resulted in very straight paths. Resorting a Euclidian Heuristic seemed to fixed it as opposed to use the Manhattan approach. The 2nd problem I ran into was when i tried added tile costs. I was hoping to use the value's of the flags that i set on the tiles but the value's were too small to make the pathfinder consider them a huge obstacle so i increased their value's but that breaks the flags a certain way and no paths were found anymore. So my questions, before posting the code, are: What am I doing wrong that the Manhatten heuristic isnt working? What ways can I store the tile costs? I was hoping to (ab)use the enum flags for this The path finder isnt considering the chance that no path is available, how do i check this? Any code optimisations are welcome as I'd love to improve my coding. public static List<Tile> FindPath( Tile startTile, Tile endTile, Tile[,] map ) { return FindPath( startTile, endTile, map, TileFlags.WALKABLE ); } public static List<Tile> FindPath( Tile startTile, Tile endTile, Tile[,] map, TileFlags acceptedFlags ) { List<Tile> open = new List<Tile>(); List<Tile> closed = new List<Tile>(); open.Add( startTile ); Tile tileToCheck; do { tileToCheck = open[0]; closed.Add( tileToCheck ); open.Remove( tileToCheck ); for( int i = 0; i < tileToCheck.neighbors.Count; i++ ) { Tile tile = tileToCheck.neighbors[ i ]; //has the node been processed if( !closed.Contains( tile ) && ( tile.flags & acceptedFlags ) != 0 ) { //Not in the open list? if( !open.Contains( tile ) ) { //Set G int G = 10; G += tileToCheck.G; //Set Parent tile.parentX = tileToCheck.x; tile.parentY = tileToCheck.y; tile.G = G; //tile.H = Math.Abs(endTile.x - tile.x ) + Math.Abs( endTile.y - tile.y ) * 10; //TODO omg wtf and other incredible stories tile.H = Vector2.Distance( new Vector2( tile.x, tile.y ), new Vector2(endTile.x, endTile.y) ); tile.Cost = tile.G + tile.H + (int)tile.flags; //Calculate H; Manhattan style open.Add( tile ); } //Update the cost if it is else { int G = 10;//cost of going to non-diagonal tiles G += map[ tile.parentX, tile.parentY ].G; //If this path is shorter (G cost is lower) then change //the parent cell, G cost and F cost. if ( G < tile.G ) //if G cost is less, { tile.parentX = tileToCheck.x; //change the square's parent tile.parentY = tileToCheck.y; tile.G = G;//change the G cost tile.Cost = tile.G + tile.H + (int)tile.flags; // add terrain cost } } } } //Sort costs open = open.OrderBy( o => o.Cost).ToList(); } while( tileToCheck != endTile ); closed.Reverse(); List<Tile> validRoute = new List<Tile>(); Tile currentTile = closed[ 0 ]; validRoute.Add( currentTile ); do { //Look up the parent of the current cell. currentTile = map[ currentTile.parentX, currentTile.parentY ]; currentTile.renderer.material.color = Color.green; //Add tile to list validRoute.Add( currentTile ); } while ( currentTile != startTile ); validRoute.Reverse(); return validRoute; } And my Tile class: [Flags] public enum TileFlags: int { NONE = 0, DIRT = 1, STONE = 2, WATER = 4, BUILDING = 8, //handy WALKABLE = DIRT | STONE | NONE, endofenum } public class Tile : MonoBehaviour { //Tile Properties public int x, y; public TileFlags flags = TileFlags.DIRT; public Transform cachedTransform; //A* properties public int parentX, parentY; public int G; public float Cost; public float H; public List<Tile> neighbors = new List<Tile>(); void Awake() { cachedTransform = transform; } }

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  • Error in my Separating Axis Theorem collision code

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Rotations and Origins

    - by Theodore Enderby
    I was hoping someone could explain to me, or help me understand, the math behind rotations and origins. I'm working on a little top down space sim and I can rotate my ship just how I want it. Now, when I get my blasters going it'd be nice if they shared the same rotation. Here's a picture. and here's some code! blast.X = ship.X+5; blast.Y = ship.Y; blast.RotationAngle = ship.RotationAngle; blast.Origin = new Vector2(ship.Origin.X,ship.Origin.Y); I add five so the sprite adds up when facing right. I tried adding five to the blast origin but no go. Any help is much appreciated

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  • Why does a computer science degree matter to a professional programmer?

    - by P.Brian.Mackey
    I have a degree in computer science. It has been great for opening doors, getting a job. As far as helping me in the professional field of C# .NET programming (the most popular platform and language in the area I work if not the entire united states on hands down the most popular OS in the world) its hardly useful. Why do you think it helps you as a programmer in your professional career (outside spouting off to prims algorithm to impress some interviewer)? In today's world adaptation, a quick mind, strong communication, OO and fundamental design skills enable a developer to write software that a customer will accept. These skills are only skimmed over in the cs program. In my mind, reading a 500 page C# book by Wrox offers far more useable a skillset than 4 years of the comp sci math blaster courses. Many disagree. So, why does a computer science degree matter?

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  • Can this word search algorithm be made faster?

    - by Ashwin Singh
    Problem: Find a match of word S in text T Given: S and T are part of spoken and written English. Example: Match 'Math' in 'I love Mathematics' NOTE: Ignore CASES. My algorithm: STEP 1) Convert S, T to char[] STEP 2) for i=0, i < T.length , i++ STEP 3) for j=S.length-1, j>0 , j-- STEP 3 is the magic, instead of going about matching M,A,T,H, this matches M, H, T and finally A. This helps in eliminating a lot of possible partial matches. For example, if I go sequentially like M A as in Boyer Moore's method ... it can match Matter, Mass, Matchstick etc. using M _ _ H will bring down size of partial matches. STEP 4) if S[j]!=T[i] -> break; else if j==i -> PRINT MATCH

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  • What are the basic skills a beginner JavaScript programmer should have?

    - by Sanford
    In NYC, we are working on creating a collaborative community programming environment and trying to segment out software engineers into differing buckets. At present, we are trying to define: Beginners Intermediates Advanced Experts (and/or Masters) Similar to an apprenticeship, you would need to demonstrate specific skills to achieve different levels. Right now, we have identified beginner programming skills as: Object - method, attributes, inheritance Variable - math, string, array, boolean - all are objects Basic arithmetic functions - precedence of functions String manipulation Looping - flow control Conditionals - boolean algebra This is a first attempt, and it is a challenge since we know the natural tension between programming and software engineering. How would you create such a skills-based ranking for JavaScript in this manner? For example, what would be the beginner JavaScript skills that you would need to have to advance to the intermediate training? And so on.

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  • How to move a line of sprites in a sine wave?

    - by electroflame
    So, I'm spawning a horizontal line of enemies that I would like to have move in a nice wave. Currently I tried: Enemy.position.X += Enemy.velocity.X; Enemy.position.Y += -(float)Math.Cos(Enemy.position.X / 200) * 5; This...kind of works. But the wave is not a true wave. The top and bottom of one pass are not the same (e.g. 5 for the top, and -5 for the bottom (I don't mean literal points, I just meant that it's not symmetrical)). Is there a better way to do this? I would like the whole line to move in a wave, so it looks fluid. By that, I mean that it should look like each enemy is "following" the one in front of it. The code I posted does have this fluidity to it, but like I said, it's not a perfect wave. Any ideas? Thanks in advance.

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  • Drawing a random x,y grid of objects within a prespective

    - by T Reddy
    I'm wrapping my head around OpenGL ES 2.0 and I think I'm trying to do something very simple, but I think the math may be eluding me. I created a simple, flat-ish cylinder in Blender that is 2 units in diameter. I want to create an arbitrary grid of these edge to edge (think of a checker board). I'm using a 3D perspective with GLKit: CGSize size = [[self view] bounds].size; _projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(45.0f), size.width/size.height, 0.1f, 100.0f); So, I managed to manually get all of these cylinders drawn on the screen just fine. However, I would like to understand how I can programmatically "fit" all of these cylinders on the screen at the same time given the camera location, screen size, cylinder diameter, and the number of rows/columns. So the net effect is that for small grids (i.e., 5x5) the objects are closer to the camera, but for large grids (i.e., 30x30) the objects are farther away. In either case, all of the cylinders are visible.

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  • what is itunes result sorted by ?

    - by NemesisII
    This is my App on Itunes: http://itunes.apple.com/us/app/buddy-calculator/id445261163?mt=8 My app Key word is : "calculator scientific calc equation math mathematics unit converter conversion statistic algebra" But when I search "Calculator" on Itunes, my app is not appeared (in first two pages). So I want to ask a question that how to improve the rank of my app , and what is the searched result sorted by (new first, vote or downloaded or ...) ? If I want to improve the rank, how can I do, does it cost fee or something ? Thanks you very much ^^ !

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  • Resources for Virtual Machine programming

    - by good_computer
    I am a beginner (a little more than that) programmer of C. I am really interested in the field of Virtual Machines. When I read about the Python VM, the PyPy project, the advancements in JVM technology, Google V8, the Erlang VM, I really get excited about these amazing pieces of technology, and really want to get my hands dirty building them or contributing to one of these projects. I need to know.. what are the things (language, concepts, algorithms, math, etc?) I need to know/learn to be able to build a virtual machine any books or other resources that will be helpful career prospects for a virtual machine engineer (but this is least important for me for now) (one more side question: somewhere I'd read something like JVM is on the cutting edge of virtual machine technology -- that it is the most advanced VM so far -- is that true?) Please give me a LONG answer detailing all that you know.

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  • How to Implement Single Sign-On between Websites

    - by hmloo
    Introduction Single sign-on (SSO) is a way to control access to multiple related but independent systems, a user only needs to log in once and gains access to all other systems. a lot of commercial systems that provide Single sign-on solution and you can also choose some open source solutions like Opensso, CAS etc. both of them use centralized authentication and provide more robust authentication mechanism, but if each system has its own authentication mechanism, how do we provide a seamless transition between them. Here I will show you the case. How it Works The method we’ll use is based on a secret key shared between the sites. Origin site has a method to build up a hashed authentication token with some other parameters and redirect the user to the target site. variables Status Description ssoEncode required hash(ssoSharedSecret + , + ssoTime + , + ssoUserName) ssoTime required timestamp with format YYYYMMDDHHMMSS used to prevent playback attacks ssoUserName required unique username; required when a user is logged in Note : The variables will be sent via POST for security reasons Building a Single Sign-On Solution Origin Site has function to 1. Create the URL for your Request. 2. Generate required authentication parameters 3. Redirect to target site. using System; using System.Web.Security; using System.Text; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { string postbackUrl = "http://www.targetsite.com/sso.aspx"; string ssoTime = DateTime.Now.ToString("yyyyMMddHHmmss"); string ssoUserName = User.Identity.Name; string ssoSharedSecret = "58ag;ai76"; // get this from config or similar string ssoHash = FormsAuthentication.HashPasswordForStoringInConfigFile(string.Format("{0},{1},{2}", ssoSharedSecret, ssoTime, ssoUserName), "md5"); string value = string.Format("{0}:{1},{2}", ssoHash,ssoTime, ssoUserName); Response.Clear(); StringBuilder sb = new StringBuilder(); sb.Append("<html>"); sb.AppendFormat(@"<body onload='document.forms[""form""].submit()'>"); sb.AppendFormat("<form name='form' action='{0}' method='post'>", postbackUrl); sb.AppendFormat("<input type='hidden' name='t' value='{0}'>", value); sb.Append("</form>"); sb.Append("</body>"); sb.Append("</html>"); Response.Write(sb.ToString()); Response.End(); } } Target Site has function to 1. Get authentication parameters. 2. Validate the parameters with shared secret. 3. If the user is valid, then do authenticate and redirect to target page. 4. If the user is invalid, then show errors and return. using System; using System.Web.Security; using System.Text; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { if (User.Identity.IsAuthenticated) { Response.Redirect("~/Default.aspx"); } } if (Request.Params.Get("t") != null) { string ticket = Request.Params.Get("t"); char[] delimiters = new char[] { ':', ',' }; string[] ssoVariable = ticket.Split(delimiters, StringSplitOptions.None); string ssoHash = ssoVariable[0]; string ssoTime = ssoVariable[1]; string ssoUserName = ssoVariable[2]; DateTime appTime = DateTime.MinValue; int offsetTime = 60; // get this from config or similar try { appTime = DateTime.ParseExact(ssoTime, "yyyyMMddHHmmss", null); } catch { //show error return; } if (Math.Abs(appTime.Subtract(DateTime.Now).TotalSeconds) > offsetTime) { //show error return; } bool isValid = false; string ssoSharedSecret = "58ag;ai76"; // get this from config or similar string hash = FormsAuthentication.HashPasswordForStoringInConfigFile(string.Format("{0},{1},{2}", ssoSharedSecret, ssoTime, ssoUserName), "md5"); if (string.Compare(ssoHash, hash, true) == 0) { if (Math.Abs(appTime.Subtract(DateTime.Now).TotalSeconds) > offsetTime) { //show error return; } else { isValid = true; } } if (isValid) { //Do authenticate; } else { //show error return; } } else { //show error } } } Summary This is a very simple and basic SSO solution, and its main advantage is its simplicity, only needs to add a single page to do SSO authentication, do not need to modify the existing system infrastructure.

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  • Why does my program stutter so much?

    - by user36322
    I've been very frustrated trying to solve this. I've looked it up, and all the answers are the same: set IsFixedTimeStep = false. This doesn't help me at all, the program is still jittery and stutters. I have absolutely no idea what is going on, can you guys help? Code for movement (objects is a list): speed = Math.Min(speed + (speedIncrement * gameTime.ElapsedGameTime.Milliseconds / 200), maxSpeed); for (int i = objects.Count - 1; i >= 0; i--) { objects[i].rect.Y += (int)(speed * gameTime.ElapsedGameTime.Milliseconds); //Check if the object is past the screen. If it is, remove it if (objects[i].rect.Y > screenHeight) { objects.Remove(objects[i]); } }

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  • Music for Kids Game!

    - by Dane
    I'm developing a Multimedia Software for Kindergarten Kids. It introduce them to animals, Alphabets, Simple Math, Colors and it contain some simple games. Music is very crucial for my project and it is very important to choose the right sort of music for different sections. But unfortunately I know nothing about music. Is there a music consultant firm which can help me to choose melodies and rythmes for my project from free music available in internet. My Budget is limited but as this is mandatory and I have no knowledge or taste about music, I think I can afford to pay for this.

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