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• Calculate angle of moving ball after collision with angled or sloped wall that is a 2D line segment

  - by Ben Mc

  If you have a "ball" inside a 2D polygon, made up of say, 4 line segments that act as bounding walls, how do you calculate the angle of the ball after the collision with the irregularly sloped wall? I know how to make the ball bounce if the wall is horizontal, vertical, or at a 45 degree angle. I also have my code setup to detect a collision with the wall. I've read about dot products and normals, but I cannot figure out how to implement these in Java / Android. I'm completely stumped and feel like I've looked up everything 10 pages deep in Google 10 times now. I'm burned out trying to figure this out, I hope someone can help.

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• Fitting place names into map shapes

  - by Old Man

  I'm drawing shapes using GDI+ using a list of lat/lon floats, and I need to place the name of the place within the borders of the polygon. Simply centering the text in the bounding rectangle doesn't work for irregular shapes. I have the text and the font so I can get the size of the rectangle that the text will need to fit in, but at that point I'm stuck. This seems like a common problem that all mapping software solves, as well as the kind of thing you would find in an algorithm or computer graphics textbook. So, given a list of floats for a polygon and a rectangle, is there a way to get the best possible point to place the text, using: 1) GDI+; 2) SQL Server Geospatial; or 3) c# code (or c, pseudocode, etc)

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• F# and ArcObjects, Part 3

  - by Marko Apfel

  Today i played a little bit with IFeature-sequences and piping data. The result was a calculator of the bounding box around all features in a feature class. Maybe a little bit dirty, but for learning was it OK. ;-) open System;; #I "C:\Program Files\ArcGIS\DotNet";; #r "ESRI.ArcGIS.System.dll";; #r "ESRI.ArcGIS.DataSourcesGDB.dll";; #r "ESRI.ArcGIS.Geodatabase.dll";; #r "ESRI.ArcGIS.Geometry.dll";; open ESRI.ArcGIS.esriSystem;; open ESRI.ArcGIS.DataSourcesGDB;; open ESRI.ArcGIS.Geodatabase;; open ESRI.ArcGIS.Geometry; let aoInitialize = new AoInitializeClass();; let status = aoInitialize.Initialize(esriLicenseProductCode.esriLicenseProductCodeArcEditor);; let workspacefactory = new SdeWorkspaceFactoryClass();; let connection = "SERVER=okul;DATABASE=p;VERSION=sde.default;INSTANCE=sde:sqlserver:okul;USER=s;PASSWORD=g";; let workspace = workspacefactory.OpenFromString(connection, 0);; let featureWorkspace = (box workspace) :?> IFeatureWorkspace;; let featureClass = featureWorkspace.OpenFeatureClass("Praxair.SFG.BP_L_ROHR");; let queryFilter = new QueryFilterClass();; let featureCursor = featureClass.Search(queryFilter, true);; let featureCursorSeq (featureCursor : IFeatureCursor) = let actualFeature = ref (featureCursor.NextFeature()) seq { while (!actualFeature) <> null do yield actualFeature do actualFeature := featureCursor.NextFeature() };; let min x y = if x < y then x else y;; let max x y = if x > y then x else y;; let info s (x : IEnvelope) = printfn "%s xMin:{%f} xMax: {%f} yMin:{%f} yMax: {%f}" s x.XMin x.XMax x.YMin x.YMax;; let con (env1 : IEnvelope) (env2 : IEnvelope) = let env = (new EnvelopeClass()) :> IEnvelope env.XMin <- min env1.XMin env2.XMin env.XMax <- max env1.XMax env2.XMax env.YMin <- min env1.YMin env2.YMin env.YMax <- max env1.YMax env2.YMax info "Intermediate" env env;; let feature = featureClass.GetFeature(100);; let ext = feature.Extent;; let BoundingBox featureClassName = let featureClass = featureWorkspace.OpenFeatureClass(featureClassName) let queryFilter = new QueryFilterClass() let featureCursor = featureClass.Search(queryFilter, true) let featureCursorSeq (featureCursor : IFeatureCursor) = let actualFeature = ref (featureCursor.NextFeature()) seq { while (!actualFeature) <> null do yield actualFeature do actualFeature := featureCursor.NextFeature() } featureCursorSeq featureCursor |> Seq.map (fun feature -> (!feature).Extent) |> Seq.fold (fun (acc : IEnvelope) a -> info "Intermediate" acc (con acc a)) ext ;; let boundingBox = BoundingBox "Praxair.SFG.BP_L_ROHR";; info "Ende-Info:" boundingBox;;

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• Speeding up procedural texture generation

  - by FalconNL

  Recently I've begun working on a game that takes place in a procedurally generated solar system. After a bit of a learning curve (having neither worked with Scala, OpenGL 2 ES or Libgdx before), I have a basic tech demo going where you spin around a single procedurally textured planet: The problem I'm running into is the performance of the texture generation. A quick overview of what I'm doing: a planet is a cube that has been deformed to a sphere. To each side, a n x n (e.g. 256 x 256) texture is applied, which are bundled in one 8n x n texture that is sent to the fragment shader. The last two spaces are not used, they're only there to make sure the width is a power of 2. The texture is currently generated on the CPU, using the updated 2012 version of the simplex noise algorithm linked to in the paper 'Simplex noise demystified'. The scene I'm using to test the algorithm contains two spheres: the planet and the background. Both use a greyscale texture consisting of six octaves of 3D simplex noise, so for example if we choose 128x128 as the texture size there are 128 x 128 x 6 x 2 x 6 = about 1.2 million calls to the noise function. The closest you will get to the planet is about what's shown in the screenshot and since the game's target resolution is 1280x720 that means I'd prefer to use 512x512 textures. Combine that with the fact the actual textures will of course be more complicated than basic noise (There will be a day and night texture, blended in the fragment shader based on sunlight, and a specular mask. I need noise for continents, terrain color variation, clouds, city lights, etc.) and we're looking at something like 512 x 512 x 6 x 3 x 15 = 70 million noise calls for the planet alone. In the final game, there will be activities when traveling between planets, so a wait of 5 or 10 seconds, possibly 20, would be acceptable since I can calculate the texture in the background while traveling, though obviously the faster the better. Getting back to our test scene, performance on my PC isn't too terrible, though still too slow considering the final result is going to be about 60 times worse: 128x128 : 0.1s 256x256 : 0.4s 512x512 : 1.7s This is after I moved all performance-critical code to Java, since trying to do so in Scala was a lot worse. Running this on my phone (a Samsung Galaxy S3), however, produces a more problematic result: 128x128 : 2s 256x256 : 7s 512x512 : 29s Already far too long, and that's not even factoring in the fact that it'll be minutes instead of seconds in the final version. Clearly something needs to be done. Personally, I see a few potential avenues, though I'm not particularly keen on any of them yet: Don't precalculate the textures, but let the fragment shader calculate everything. Probably not feasible, because at one point I had the background as a fullscreen quad with a pixel shader and I got about 1 fps on my phone. Use the GPU to render the texture once, store it and use the stored texture from then on. Upside: might be faster than doing it on the CPU since the GPU is supposed to be faster at floating point calculations. Downside: effects that cannot (easily) be expressed as functions of simplex noise (e.g. gas planet vortices, moon craters, etc.) are a lot more difficult to code in GLSL than in Scala/Java. Calculate a large amount of noise textures and ship them with the application. I'd like to avoid this if at all possible. Lower the resolution. Buys me a 4x performance gain, which isn't really enough plus I lose a lot of quality. Find a faster noise algorithm. If anyone has one I'm all ears, but simplex is already supposed to be faster than perlin. Adopt a pixel art style, allowing for lower resolution textures and fewer noise octaves. While I originally envisioned the game in this style, I've come to prefer the realistic approach. I'm doing something wrong and the performance should already be one or two orders of magnitude better. If this is the case, please let me know. If anyone has any suggestions, tips, workarounds, or other comments regarding this problem I'd love to hear them.

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• 2D Skeletal Animation Transformations

  - by Brad Zeis

  I have been trying to build a 2D skeletal animation system for a while, and I believe that I'm fairly close to finishing. Currently, I have the following data structures: struct Bone { Bone *parent; int child_count; Bone **children; double x, y; }; struct Vertex { double x, y; int bone_count; Bone **bones; double *weights; }; struct Mesh { int vertex_count; Vertex **vertices; Vertex **tex_coords; } Bone->x and Bone->y are the coordinates of the end point of the Bone. The starting point is given by (bone->parent->x, bone->parent->y) or (0, 0). Each entity in the game has a Mesh, and Mesh->vertices is used as the bounding area for the entity. Mesh->tex_coords are texture coordinates. In the entity's update function, the position of the Bone is used to change the coordinates of the Vertices that are bound to it. Currently what I have is: void Mesh_update(Mesh *mesh) { int i, j; double sx, sy; for (i = 0; i < vertex_count; i++) { if (mesh->vertices[i]->bone_count == 0) { continue; } sx, sy = 0; for (j = 0; j < mesh->vertices[i]->bone_count; j++) { sx += (/* ??? */) * mesh->vertices[i]->weights[j]; sy += (/* ??? */) * mesh->vertices[i]->weights[j]; } mesh->vertices[i]->x = sx; mesh->vertices[i]->y = sy; } } I think I have everything I need, I just don't know how to apply the transformations to the final mesh coordinates. What tranformations do I need here? Or is my approach just completely wrong?

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• Get to Know a Candidate (8 of 25): Rocky Anderson&ndash;Justice Party

  - by Brian Lanham

  DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Ross Carl “Rocky” Anderson served two terms as the 33rd mayor of Salt Lake City, Utah, between 2000 and 2008.  He is the Executive Director of High Road for Human Rights.  Prior to serving as Mayor, he practiced law for 21 years in Salt Lake City, during which time he was listed in Best Lawyers in America, was rated A-V (highest rating) by Martindale-Hubbell, served as Chair of the Utah State Bar Litigation Section[4] and was Editor-in-Chief of, and a contributor to, Voir Dire legal journal. As mayor, Anderson rose to nationwide prominence as a champion of several national and international causes, including climate protection, immigration reform, restorative criminal justice, LGBT rights, and an end to the "war on drugs". Before and after the invasion by the U.S. of Iraq in 2003, Anderson was a leading opponent of the invasion and occupation of Iraq and related human rights abuses. Anderson was the only mayor of a major U.S. city who advocated for the impeachment of President George W. Bush, which he did in many venues throughout the United States. Anderson's work and advocacy led to local, national, and international recognition in numerous spheres, including being named by Business Week as one of the top twenty activists in the world on climate change,serving on the Newsweek Global Environmental Leadership Advisory Board, and being recognized by the Human Rights Campaign as one of the top ten straight advocates in the United States for LGBT equality. He has also received numerous awards for his work, including the EPA Climate Protection Award, the Sierra Club Distinguished Service Award, the Respect the Earth Planet Defender Award, the National Association of Hispanic Publications Presidential Award, The Drug Policy Alliance Richard J. Dennis Drugpeace Award, the Progressive Democrats of America Spine Award, the League of United Latin American Citizens Profile in Courage Award, the Bill of Rights Defense Committee Patriot Award, the Code Pink (Salt Lake City) Pink Star honor, the Morehouse University Gandhi, King, Ikeda Award, and the World Leadership Award for environmental programs. Formerly a member of the Democratic Party, Anderson expressed his disappointment with that Party in 2011, stating, “The Constitution has been eviscerated while Democrats have stood by with nary a whimper. It is a gutless, unprincipled party, bought and paid for by the same interests that buy and pay for the Republican Party." Anderson announced his intention to run for President in 2012 as a candidate for the newly-formed Justice Party. Although founded by Rocky Anderson of Utah, the Justice Party was first recognized by Mississippi and describes itself as advocating economic justice through measures such as green jobs and a right to organize, environment justice through enforcing employee safeguards in trade agreements, and social and civic justice through universal health care. In its first press release, the Utah Justice Party set forth its goals for justice in the economic, environmental, social and civic realms, along with a call to rid the corrupting influence of big money from government, to reverse the erosion of rights guaranteed by the Constitution, and to stop draining American resources to support illegal wars of aggression. Its press release says its grassroots supporters believe that now is the time for all to "shed their skeptical view that their voices don't matter", that "our 2-party system is a 'duopoly' controlled by the same corporate and military interests", and that the people must act to ensure "that our nation will achieve a brighter, sustainable future.” Anderson has ballot access in CO, CT, FL, ID, LA, MI, MN, MS, NJ, NM, OR, RI, TN, UT, VT, WA (152 electoral votes) and has write-in access in AL, AK, DE, GA, IL, IO, KS, MD, MO, NE, NH, NY, PA, TX Learn more about Rocky Anderson and Justice Party on Wikipedia.

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• Largest sphere inside a frustum

  - by Will

  How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. We can unproject all eight corners of the frusum, and the centres of the near and far ends. So we know point 1, 3 and 4. We also know that point 2 is the same distance from 3 as 4 is from 3. So then we can compute the nearest point on the line 1 to 4 to point 2 in order to get the centre? But the actual math and code escapes me. I want to draw models (which are approximately spherical and which I have a miniball bounding sphere for) as large as possible. Update: I've tried to implement the incircle-on-two-planes approach as suggested by bobobobo and Nathan Reed : function getFrustumsInsphere(viewport,invMvpMatrix) { var midX = viewport[0]+viewport[2]/2, midY = viewport[1]+viewport[3]/2, centre = unproject(midX,midY,null,null,viewport,invMvpMatrix), incircle = function(a,b) { var c = ray_ray_closest_point_3(a,b); a = a[1]; // far clip plane b = b[1]; // far clip plane c = c[1]; // camera var A = vec3_length(vec3_sub(b,c)), B = vec3_length(vec3_sub(a,c)), C = vec3_length(vec3_sub(a,b)), P = 1/(A+B+C), x = ((A*a[0])+(B*a[1])+(C*a[2]))*P, y = ((A*b[0])+(B*b[1])+(C*b[2]))*P, z = ((A*c[0])+(B*c[1])+(C*c[2]))*P; c = [x,y,z]; // now the centre of the incircle c.push(vec3_length(vec3_sub(centre[1],c))); // add its radius return c; }, left = unproject(viewport[0],midY,null,null,viewport,invMvpMatrix), right = unproject(viewport[2],midY,null,null,viewport,invMvpMatrix), horiz = incircle(left,right), top = unproject(midX,viewport[1],null,null,viewport,invMvpMatrix), bottom = unproject(midX,viewport[3],null,null,viewport,invMvpMatrix), vert = incircle(top,bottom); return horiz[3]<vert[3]? horiz: vert; } I admit I'm winging it; I'm trying to adapt 2D code by extending it into 3 dimensions. It doesn't compute the insphere correctly; the centre-point of the sphere seems to be on the line between the camera and the top-left each time, and its too big (or too close). Is there any obvious mistakes in my code? Does the approach, if fixed, work?

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• Picture rendered from above and below using an Orthographic camera do not match

  - by Roy T.

  I'm using an orthographic camera to render slices of a model (in order to voxelize it). I render each slice both from above and below in order to determine what is inside each slice. I am using an orthographic camera The model I render is a simple 'T' shape constructed from two cubes. The cubes have the same dimensions and have the same Y (height) coordinate. See figure 1 for a render of it in Blender. I render this model once directly from above and once directly from below. My expectation was that I would get exactly the same image (except for mirroring over the y-axis). However when I render using a very low resolution render target (25x25) the position (in pixels) of the 'T' is different when rendered from above as opposed to rendered from below. See figure 2 and 3. The pink blocks are not part of the original rendering but I've added them so you can easily count/see the differences. Figure 2: the T rendered from above Figure 3: the T rendered from below This is probably due to what I've read about pixel and texel coordinates which might be biased to the top-left as seen from the camera. Since I'm using the same 'up' vector for both of my camera's my bias only shows on the x-axis. I've tried to change the position of the camera and it's look-at by, what I thought, should be half a pixel. I've tried both shifting a single camera and shifting both cameras and while I see some effect I am not able to get a pixel-by-pixel perfect copy from both camera's. Here I initialize the camera and compute, what I believe to be, half pixel. boundsDimX and boundsDimZ is a slightly enlarged bounding box around the model which I also use as the width and height of the view volume of the orthographic camera. Matrix projection = Matrix.CreateOrthographic(boundsDimX, boundsDimZ, 0.5f, sliceHeight + 0.5f); Vector3 halfPixel = new Vector3(boundsDimX / (float)renderTarget.Width, 0, boundsDimY / (float)renderTarget.Height) * 0.5f; This is the code where I set the camera position and camera look ats // Position camera if (downwards) { float cameraHeight = bounds.Max.Y + 0.501f - (sliceHeight * i); Vector3 cameraPosition = new Vector3 ( boundsCentre.X, // possibly adjust by half a pixel? cameraHeight, boundsCentre.Z ); camera.Position = cameraPosition; camera.LookAt = new Vector3(cameraPosition.X, cameraHeight - 1.0f, cameraPosition.Z); } else { float cameraHeight = bounds.Max.Y - 0.501f - (sliceHeight * i); Vector3 cameraPosition = new Vector3 ( boundsCentre.X, cameraHeight, boundsCentre.Z ); camera.Position = cameraPosition; camera.LookAt = new Vector3(cameraPosition.X, cameraHeight + 1.0f, cameraPosition.Z); } Main Question Now you've seen all the problems and code you can guess it. My main question is. How do I align both camera's so that they each render exactly the same image (mirrored along the Y axis)? Figure 1 the original model rendered in blender

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• Android Touch Event Collision Detection

  - by chrissb

  I'm relatively new to both Java and Android, so hopefully the problem I'm having is stemming from something pretty minor that I've overlooked. I've got a (very early stage) game that I've started working on, for Android using Java. At this stage, when the user touches the screen, if they touched a point at which there is an enemy, the enemies health is decreased and they become immobile (for the current implementation at least). The issue that I'm having is that the touch detection doesn't always seem to work. I've got a testing sprite set up that goes to the eventX and eventY coordinates of the touch down event, and it always seems to collide with the enemy object. Yet, the enemy doesn't always register as being hit, and sometimes a hit is registered when the sprite indicates the touch coordinates were outside of the enemies bounding box. I realise that this probably doesn't mean much without any code, so here's what I've got so far. Be gentle, as this is literally my first attempt at something more than basic movement etc. First off, the MainGamePanel class registers the touch event, and informs the levelmanager class (which is what I set up to monitor/handle enemies) public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN){ levelManager.handleActionDown((int)event.getX(), (int)event.getY()); targetX=event.getX(); targetY=event.getY(); } if (event.getAction() == MotionEvent.ACTION_MOVE) { //the gestures } if (event.getAction() == MotionEvent.ACTION_UP) { //touch was released } return true; } From there, in the levelmanager class the touch event is passed on to all of the enemies within a list array: public static void handleActionDown(int eventX,int eventY){ hit=false; for (enemy1 en : enemy1array){ en.handleActionDown(eventX, eventY); } } The rest of the collision code is handled within the enemies handleActionDown function: public void handleActionDown(int eventX, int eventY) { if(eventX>this.x-enemy1bitmap.getWidth() && eventX<this.x+enemy1bitmap.getWidth() && eventY>this.y-enemy1bitmap.getHeight() && eventY<this.x+enemy1bitmap.getHeight()){ takeDamage(1); levelmanager.setHit(); } } I should probably be using getWidth()/2 and getHeight()/2 for it to be more accurate, but I expanded the area to test this - although I've noticed no improvement. At this stage, the games detection over whether or not the enemy is hit is spotty at best. Generally it takes two or three attempts before a collision is successfully registered, even though the sprite that is being used for testing and set to the eventX and eventY coordinates always indicates that the collision should have worked. Hopefully someone can steer me in the right direction here, and if more information is needed, ask away! Cheers, -Chris

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• x axis detection issues platformer starter kit

  - by dbomb101

  I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either direction on the x axis, could someone could tell me why this happens ? Here is the collision method. /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, TileCollision collision = Level.GetCollision(x, y); if (collision != TileCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == TileCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == TileCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } //This is the section which deals with collision on the x-axis else if (collision == TileCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; }

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• Creating a frozen bubble clone

  - by Vaughan Hilts

  This photo illustrates the environment: http://i.imgur.com/V4wbp.png I'll shoot the cannon, it'll bounce off the wall and it's SUPPOSED to stick to the bubble. It does at pretty much every other angle. The problem is always reproduced here, when hit off the wall into those bubbles. It also exists in other cases, but I'm not sure what triggers it. What actually happens: The ball will sometimes set to the wrong cell, and my "dropping" code will detect it as a loner and drop it off the stage. *There are many implementations of "Frozen Bubble" on the web, but I can't for the life of me find a good explanation as to how the algorithm for the "Bubble Sticking" works. * I see this: http://www.wikiflashed.com/wiki/BubbleBobble https://frozenbubblexna.svn.codeplex.com/svn/FrozenBubble/ But I can't figure out the algorithims... could anyone explain possibly the general idea behind getting the balls to stick? Code in question: //Counstruct our bounding rectangle for use var nX = currentBall.x + ballvX * gameTime; var nY = currentBall.y - ballvY * gameTime; var movingRect = new BoundingRectangle(nX, nY, 32, 32); var able = false; //Iterate over the cells and draw our bubbles for (var x = 0; x < 8; x++) { for (var y = 0; y < 12; y++) { //Get the bubble at this layout var bubble = bubbleLayout[x][y]; var rowHeight = 27; //If this slot isn't empty, draw if (bubble != null) { var bx = 0, by = 0; if (y % 2 == 0) { bx = x * 32 + 270; by = y * 32 + 45; } else { bx = x * 32 + 270 + 16; by = y * 32 + 45; } //Check var targetBox = new BoundingRectangle(bx, by, 32, 32); if (targetBox.intersects(movingRect)) { able = true; } } } } cellY = Math.round((currentBall.y - 45) / 32); if (cellY % 2 == 0) cellX = Math.round((currentBall.x - 270) / 32); else cellX = Math.round((currentBall.x - 270 - 16) / 32); Any ideas are very much welcome. Things I've tried: Flooring and Ceiling values Changing the wall bounce to a lower value Slowing down the ball None of these seem to affect it. Is there something in my math I'm not getting?

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• Finding furthermost point in game world

  - by user13414

  I am attempting to find the furthermost point in my game world given the player's current location and a normalized direction vector in screen space. My current algorithm is: convert player world location to screen space multiply the direction vector by a large number (2000) and add it to the player's screen location to get the distant screen location convert the distant screen location to world space create a line running from the player's world location to the distant world location loop over the bounding "walls" (of which there are always 4) of my game world check whether the wall and the line intersect if so, where they intersect is the furthermost point of my game world in the direction of the vector Here it is, more or less, in code: public Vector2 GetFurthermostWorldPoint(Vector2 directionVector) { var screenLocation = entity.WorldPointToScreen(entity.Location); var distantScreenLocation = screenLocation + (directionVector * 2000); var distantWorldLocation = entity.ScreenPointToWorld(distantScreenLocation); var line = new Line(entity.Center, distantWorldLocation); float intersectionDistance; Vector2 intersectionPoint; foreach (var boundingWall in entity.Level.BoundingWalls) { if (boundingWall.Intersects(line, out intersectionDistance, out intersectionPoint)) { return intersectionPoint; } } Debug.Assert(false, "No intersection found!"); return Vector2.Zero; } Now this works, for some definition of "works". I've found that the further out my distant screen location is, the less chance it has of working. When digging into the reasons why, I noticed that calls to Viewport.Unproject could result in wildly varying return values for points that are "far away". I wrote this stupid little "test" to try and understand what was going on: [Fact] public void wtf() { var screenPositions = new Vector2[] { new Vector2(400, 240), new Vector2(400, -2000), }; var viewport = new Viewport(0, 0, 800, 480); var projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, viewport.Width / viewport.Height, 1, 200000); var viewMatrix = Matrix.CreateLookAt(new Vector3(400, 630, 600), new Vector3(400, 345, 0), new Vector3(0, 0, 1)); var worldMatrix = Matrix.Identity; foreach (var screenPosition in screenPositions) { var nearPoint = viewport.Unproject(new Vector3(screenPosition, 0), projectionMatrix, viewMatrix, worldMatrix); var farPoint = viewport.Unproject(new Vector3(screenPosition, 1), projectionMatrix, viewMatrix, worldMatrix); Console.WriteLine("For screen position {0}:", screenPosition); Console.WriteLine(" Projected Near Point = {0}", nearPoint.TruncateZ()); Console.WriteLine(" Projected Far Point = {0}", farPoint.TruncateZ()); Console.WriteLine(); } } The output I get on the console is: For screen position {X:400 Y:240}: Projected Near Point = {X:400 Y:629.571 Z:599.0967} Projected Far Point = {X:392.9302 Y:-83074.98 Z:-175627.9} For screen position {X:400 Y:-2000}: Projected Near Point = {X:400 Y:626.079 Z:600.7554} Projected Far Point = {X:390.2068 Y:-767438.6 Z:148564.2} My question is really twofold: what am I doing wrong with the unprojection such that it varies so wildly and, thus, does not allow me to determine the corresponding world point for my distant screen point? is there a better way altogether to determine the furthermost point in world space given a current world space location, and a directional vector in screen space?

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• About the K computer

  - by nospam(at)example.com (Joerg Moellenkamp)

  Okay ? after getting yet another mail because of the new #1 on the Top500 list, I want to add some comments from my side: Yes, the system is using SPARC processor. And that is great news for a SPARC fan like me. It is using the SPARC VIIIfx processor from Fujitsu clocked at 2 GHz. No, it isn't the only one. Most people are saying there are two in the Top500 list using SPARC (#77 JAXA and #1 K) but in fact there are three. The Tianhe-1 (#2 on the Top500 list) super computer contains 2048 Galaxy "FT-1000" 1 GHz 8-core processors. Don't know it? The FeiTeng-1000 ? this proc is a 8 core, 8 threads per core, 1 ghz processor made in China. And it's SPARC based. By the way ? this sounds really familiar to me ? perhaps the people just took the opensourced UltraSPARC-T2 design, because some of the parameters sound just to similar. However it looks like that Tianhe-1 is using the SPARCs as input nodes and not as compute notes. No, I don't see it as the next M-series processor. Simple reason: You can't create SMP systems out of them ? it simply hasn't the functionality to do so. Even when there are multiple CPUs on a single board, they are not connected like an SMP/NUMA machine to a shared memory machine ? they are connected with the cluster interconnect (in this case the Tofu interconnect) and work like a large cluster. Yes, it has a lot of oomph in Linpack ? however I assume a lot came from the extensions to the SPARCv9 standard. No, Linpack has no relevance for any commercial workload ? Linpack is such a special load, that even some HPC people are arguing that it isn't really a good benchmark for HPC. It's embarrassingly parallel, it can work with relatively small interconnects compared to the interconnects in SMP systems (however we get in spheres SMP interconnects where a few years ago). Amdahl isn't hitting that hard when running Linpack. Yes, it's a good move to use SPARC. At some time in the last 10 years, there was an interesting twist in perception: SPARC was considered as proprietary architecture and x86 was the open architecture. However it's vice versa ? try to create a x86 clone and you have a lot of intellectual property problems, create a SPARC clone and you have to spend 100 bucks or so to get the specification from the SPARC Foundation and develop your own SPARC processor. Fujitsu is doing this for a long time now. So they had their own processor, their own know-how. So why was SPARC a good choice? Well ? essentially Fujitsu can do what they want with their core as it is their core, for example adding the extensions to the SPARCv9 chipset ? getting Intel to create extensions to x86 to help you with your product is a little bit harder. So Fujitsu could do they needed to do with their processor in order to create such a supercomputer. No, the K is really using no FPGA or GPU as accelerators. The K is really using the CPU at doing this job. Yes, it has a significantly enhanced FPU capable to execute 8 instructions in parallel. No, it doesn't run Solaris. Yes, it uses Linux. No, it doesn't hurt me ... as my colleague Roland Rambau (he knows a lot about HPC) said once to me ... it doesn't matter which OS is staying out of the way of the workload in HPC.

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• Box2D Difference Between WorldCenter and Position

  - by Free Lancer

  So this problem has been brothering for a couple of days now. First off, what is the difference between say Body.getWorldCenter() and Body.getPosition(). I heard that WorldCenter might have to do with the center of gravity or something. Second, When I create a Box2D Body for a sprite the Body is always at the lower left corner. I check it by printing a Rectangle of 1 pixel around the box.getWorldCenter(). From what I understand the Body should be in the center of the Sprite and its bounding box should wrap around the Sprite, correct? Here's an image of what I mean (The Sprite is Red, Body Blue): Here's some code: Body Creator: public static Body createBoxBody( final World pPhysicsWorld, final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pCenterX = pSprite.getX() + pSprite.getWidth() / 2; float pCenterY = pSprite.getY() + pSprite.getHeight() / 2; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; //boxBodyDef.position.x = pCenterX / Constants.PIXEL_METER_RATIO; //boxBodyDef.position.y = pCenterY / Constants.PIXEL_METER_RATIO; boxBodyDef.position.x = pSprite.getX() / Constants.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Constants.PIXEL_METER_RATIO; Vector2 v = new Vector2( boxBodyDef.position.x * Constants.PIXEL_METER_RATIO, boxBodyDef.position.y * Constants.PIXEL_METER_RATIO ); Gdx.app.log("@Physics", "createBoxBody():: Box Position: " + v); // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Constants.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Constants.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = pPhysicsWorld.createBody(boxBodyDef); Gdx.app.log("@Physics", "createBoxBody():: Box Center: " + boxBody.getPosition().mul(Constants.PIXEL_METER_RATIO)); boxBody.createFixture(pFixtureDef); boxBody.setTransform( boxBody.getWorldCenter(), MathUtils.degreesToRadians * pRotation ); boxPoly.dispose(); return boxBody; } Making the Sprite: public Car( Texture texture, float pX, float pY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( mSprite.getWidth() / 6, mSprite.getHeight() / 6 ); mSprite.setPosition( pX, pY ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); FixtureDef carFixtureDef = new FixtureDef(); // Set the Fixture's properties, like friction, using the car's shape carFixtureDef.restitution = 1f; carFixtureDef.friction = 1f; carFixtureDef.density = 1f; // needed to rotate body using applyTorque mBody = Physics.createBoxBody( world, BodyDef.BodyType.DynamicBody, carFixtureDef, mSprite ); }

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• HTML5 platformer collision detection problem

  - by fnx

  I'm working on a 2D platformer game, and I'm having a lot of trouble with collision detection. I've looked trough some tutorials, questions asked here and Stackoverflow, but I guess I'm just too dumb to understand what's wrong with my code. I've wanted to make simple bounding box style collisions and ability to determine on which side of the box the collision happens, but no matter what I do, I always get some weird glitches, like the player gets stuck on the wall or the jumping is jittery. You can test the game here: Platform engine test. Arrow keys move and z = run, x = jump, c = shoot. Try to jump into the first pit and slide on the wall. Here's the collision detection code: function checkCollisions(a, b) { if ((a.x > b.x + b.width) || (a.x + a.width < b.x) || (a.y > b.y + b.height) || (a.y + a.height < b.y)) { return false; } else { handleCollisions(a, b); return true; } } function handleCollisions(a, b) { var a_top = a.y, a_bottom = a.y + a.height, a_left = a.x, a_right = a.x + a.width, b_top = b.y, b_bottom = b.y + b.height, b_left = b.x, b_right = b.x + b.width; if (a_bottom + a.vy > b_top && distanceBetween(a_bottom, b_top) + a.vy < distanceBetween(a_bottom, b_bottom)) { a.topCollision = true; a.y = b.y - a.height + 2; a.vy = 0; a.canJump = true; } else if (a_top + a.vy < b_bottom && distanceBetween(a_top, b_bottom) + a.vy < distanceBetween(a_top, b_top)) { a.bottomCollision = true; a.y = b.y + b.height; a.vy = 0; } else if (a_right + a.vx > b_left && distanceBetween(a_right, b_left) < distanceBetween(a_right, b_right)) { a.rightCollision = true; a.x = b.x - a.width - 3; //a.vx = 0; } else if (a_left + a.vx < b_right && distanceBetween(a_left, b_right) < distanceBetween(a_left, b_left)) { a.leftCollision = true; a.x = b.x + b.width + 3; //a.vx = 0; } } function distanceBetween(a, b) { return Math.abs(b-a); }

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• how do I add a texture to a triangle in three.js?

  - by Kae Verens

  I've created a scene which has many cubes, spheres, etc, in it, and have been able to apply textures to those primitives, but when I want to add a texture to a simple triangle, I'm totally lost. Here's the closest I've come to getting it right: var texture=THREE.ImageUtils.loadTexture('/f/3d-images/texture-steel.jpg'); var materialDecalRoof=new THREE.MeshBasicMaterial( { 'map': texture, 'wireframe': false, 'overdraw': true } ); var geometry = new THREE.Geometry(); geometry.vertices.push(new THREE.Vector3(tentX/2+1, tentY, tentZ/2+1)); geometry.vertices.push(new THREE.Vector3(0, tentT, 0)); geometry.vertices.push(new THREE.Vector3(0, tentT, 0)); geometry.vertices.push(new THREE.Vector3(-tentX/2-1, tentY, tentZ/2+1)); geometry.faces.push(new THREE.Face4(0, 1, 2, 3)); geometry.faceVertexUvs[0].push([ new THREE.UV(0, 0), new THREE.UV(0, 0), new THREE.UV(0, 0), new THREE.UV(0, 0) ]); geometry.computeFaceNormals(); geometry.computeCentroids(); geometry.computeVertexNormals(); var mesh= new THREE.Mesh( geometry, materialDecalRoof); scene.add(mesh); This does not work. All i get is a flickering triangle (when the scene is moved) where an image should be. To test this, go to https://www.poptents.eu/3dFrame.php, upload an image in the Roof section, and drag the view to see the roof flicker. Does anyone know what I'm doing wrong here?

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• Are there tools available for trimming PDF margins?

  - by Charles Duffy

  I have an ebook I'm trying to read in PDF format on a Kindle. Unfortunately, the page headers and footers have some content (page number and copyright info, respectively) preventing the device from scaling the actual text to match its usable area viewing area, thus leaving the actual content too small to read. Various tools are available which will trim off whitespace, but the Kindle already does this; my goal, by contrast, is to remove printed matter outside of a defined bounding box, and the only tool I've found for the purpose is moderately expensive commercial software. I could probably generate a mask in Inkscape; split out the individual pages using pdftk, apply the mask to each page individually (outputting to postscript), and recombine the numerous postscript files into a single PDF. However, this decode/reencode steps would be pretty unfortunate in terms of document size; something able to operate with a bit more finesse would be ideal. I have all major operating systems handy (Windows, several modern Linux distros, a Mac, etc) so solutions don't need to be constrained by platform. Suggestions? (I've reported the issue to the author, who mentioned it to his editor, who hasn't done anything about the issue over the course of more than a month, making the zero-work approach evidently nonproductive).

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• Font serialization in vb.net

  - by jovany

  Hello all, as the title says , I need to serialize my font. I have tried the following approach unfortunately to no avail. This is what I have and what happens; I have a drawing application and certain variables and properties need to be serialized. (So , Xml.Serialization has been used.) Now this has already been done in a huge portion and I've created some other attributes which needed to be serialized and it works. There is one base class and classes such as drawablestar, drawableeclipse ,etc. all inherit from this class. As does my drawabletextboxclass. The base class is Serializable as can be seen in the sample below. It looks like this... Imports System.Xml.Serialization <Serializable()> _ Public MustInherit Class Drawable ' Drawing characteristics. 'Font characteristics <XmlIgnore()> Public FontFamily As String <XmlIgnore()> Public FontSize As Integer <XmlIgnore()> Public FontType As Integer <XmlIgnore()> Public ForeColor As Color <XmlIgnore()> Public FillColor As Color <XmlAttributeAttribute()> Public LineWidth As Integer = 0 <XmlAttributeAttribute()> Public X1 As Integer <XmlAttributeAttribute()> Public Y1 As Integer <XmlAttributeAttribute()> Public X2 As Integer <XmlAttributeAttribute()> Public Y2 As Integer ' attributes for size textbox <XmlAttributeAttribute()> Public widthLabel As Integer <XmlAttributeAttribute()> Public heightLabel As Integer '<XmlTextAttribute()> Public FontFamily As String '<XmlAttributeAttribute()> Public FontSize As Integer 'this should actually not be here.. <XmlAttributeAttribute()> Public s_InsertLabel As String ' Indicates whether we should draw as selected. <XmlIgnore()> Public IsSelected As Boolean = False ' Constructors. Public Sub New() ForeColor = Color.Black FillColor = Color.White 'FontFamily = "Impact" 'FontSize = 12 End Sub Friend WriteOnly Property _Label() As String Set(ByVal Value As String) s_InsertLabel = Value End Set End Property Public Sub New(ByVal fore_color As Color, ByVal fill_color As Color, Optional ByVal line_width As Integer = 0) LineWidth = line_width ForeColor = fore_color FillColor = fill_color ' FontFamily = Font_Family ' FontSize = Font_Size End Sub ' Property procedures to serialize and ' deserialize ForeColor and FillColor. <XmlAttributeAttribute("ForeColor")> _ Public Property ForeColorArgb() As Integer Get Return ForeColor.ToArgb() End Get Set(ByVal Value As Integer) ForeColor = Color.FromArgb(Value) End Set End Property <XmlAttributeAttribute("BackColor")> _ Public Property FillColorArgb() As Integer Get Return FillColor.ToArgb() End Get Set(ByVal Value As Integer) FillColor = Color.FromArgb(Value) End Set End Property 'Property procedures to serialize and 'deserialize Font <XmlAttributeAttribute("InsertLabel")> _ Public Property InsertLabel_() As String Get Return s_InsertLabel End Get Set(ByVal value As String) s_InsertLabel = value End Set End Property <XmlAttributeAttribute("FontSize")> _ Public Property FontSizeGet() As Integer Get Return FontSize End Get Set(ByVal value As Integer) FontSize = value End Set End Property <XmlAttributeAttribute("FontFamily")> _ Public Property FontFamilyGet() As String Get Return FontFamily End Get Set(ByVal value As String) FontFamily = value End Set End Property <XmlAttributeAttribute("FontType")> _ Public Property FontType_() As Integer Get Return FontType End Get Set(ByVal value As Integer) FontType = value End Set End Property #Region "Methods to override" Public MustOverride Sub Draw(ByVal gr As Graphics) ' Return the object's bounding rectangle. Public MustOverride Function GetBounds() As Rectangle ...... ........ ..... End Class [/code] My textbox class which looks like this , is the one that needs to save it's font. Imports System.Math Imports System.Xml.Serialization Imports System.Windows.Forms <Serializable()> _ Public Class DrawableTextBox Inherits Drawable Private i_StringLength As Integer Private i_StringWidth As Integer Private drawFont As Font = New Font(FontFamily, 12, FontStyle.Regular) Private brsTextColor As Brush = Brushes.Black Private s_insertLabelTextbox As String = "label" ' Constructors. Public Sub New() End Sub Public Sub New(ByVal objCanvas As PictureBox, ByVal fore_color As Color, ByVal fill_color As Color, Optional ByVal line_width As Integer = 0, Optional ByVal new_x1 As Integer = 0, Optional ByVal new_y1 As Integer = 0, Optional ByVal new_x2 As Integer = 1, Optional ByVal new_y2 As Integer = 1) MyBase.New(fore_color, fill_color, line_width) Dim objGraphics As Graphics = objCanvas.CreateGraphics() X1 = new_x1 Y1 = new_y1 'Only rectangles ,circles and stars can resize for now b_Movement b_Movement = True Dim frm As New frmTextbox frm.MyFont = drawFont frm.ShowDialog() If frm.DialogResult = DialogResult.OK Then FontFamily = frm.MyFont.FontFamily.Name FontSize = frm.MyFont.Size FontType = frm.MyFont.Style 'drawFont = frm.MyFont drawFont = New Font(FontFamily, FontSize) drawFont = FontAttributes() brsTextColor = New SolidBrush(frm.txtLabel.ForeColor) s_InsertLabel = frm.txtLabel.Text i_StringLength = s_InsertLabel.Length 'gefixtf Dim objSizeF As SizeF = objGraphics.MeasureString(s_InsertLabel, drawFont, New PointF(X2 - X1, Y2 - Y1), New StringFormat(StringFormatFlags.NoClip)) Dim objPoint As Point = objCanvas.PointToClient(New Point(X1 + objSizeF.Width, Y1 + objSizeF.Height)) widthLabel = objSizeF.Width heightLabel = objSizeF.Height X2 = X1 + widthLabel Y2 = Y1 + heightLabel Else Throw New ApplicationException() End If End Sub ' Draw the object on this Graphics surface. Public Overrides Sub Draw(ByVal gr As System.Drawing.Graphics) ' Make a Rectangle representing this rectangle. Dim rectString As Rectangle rectString = New Rectangle(X1, Y1, widthLabel, heightLabel) rectString = GetBounds() ' See if we're selected. If IsSelected Then gr.DrawString(s_InsertLabel, drawFont, brsTextColor, X1, Y1) 'gr.DrawRectangle(Pens.Black, rect) ' Pens.Transparent gr.DrawRectangle(Pens.Black, rectString) ' Draw grab handles. DrawGrabHandle(gr, X1, Y1) DrawGrabHandle(gr, X1, Y2) DrawGrabHandle(gr, X2, Y2) DrawGrabHandle(gr, X2, Y1) Else gr.DrawString(s_InsertLabel, drawFont, brsTextColor, X1, Y1) 'gr.DrawRectangle(Pens.Black, rect) ' Pens.Transparent gr.DrawRectangle(Pens.Black, rectString) End If End Sub 'get fontattributes Public Function FontAttributes() As Font Return New Font(FontFamily, 12, FontStyle.Regular) End Function ' Return the object's bounding rectangle. Public Overrides Function GetBounds() As System.Drawing.Rectangle Return New Rectangle( _ Min(X1, X1), _ Min(Y1, Y1), _ Abs(widthLabel), _ Abs(heightLabel)) End Function ' Return True if this point is on the object. Public Overrides Function IsAt(ByVal x As Integer, ByVal y As Integer) As Boolean Return (x >= Min(X1, X2)) AndAlso _ (x <= Max(X1, X2)) AndAlso _ (y >= Min(Y1, Y2)) AndAlso _ (y <= Max(Y1, Y2)) End Function ' Move the second point. Public Overrides Sub NewPoint(ByVal x As Integer, ByVal y As Integer) X2 = x Y2 = y End Sub ' Return True if the object is empty (e.g. a zero-length line). Public Overrides Function IsEmpty() As Boolean Return (X1 = X2) AndAlso (Y1 = Y2) End Function End Class The coordinates ( X1 ,X2,Y1, Y2 ) are needed to draw a circle , rectangle etc. ( in the other classes ).This all works. If I load my saved file it shows me the correct location and correct size of drawn objects. If I open my xml file I can see all values are correctly saved ( including my FontFamily ). Also the color which can be adjusted is saved and then properly displayed when I load a previously saved drawing. Of course because the coordinates work, if I insert a textField ,the location where it is being displayed is correct. However here comes the problem , my fontSize and fontfamily don't work. As you can see I created them in the base class, However this does not work. Is my approach completely off? What can I do ? Before saving img14.imageshack.us/i/beforeos.jpg/ After loading the Font jumps back to Sans serif and size 12. I could really use some help here.. Edit: I've been using the sample from this website http://www.vb-helper.com/howto_net_drawing_framework.html

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• LibGDX Box2D Body and Sprite AND DebugRenderer out of sync

  - by Free Lancer

  I am having a couple issues with Box2D bodies. I have a GameObject holding a Sprite and Body. I use a ShapeRenderer to draw an outline of the Body's and Sprite's bounding boxes. I also added a Box2DDebugRenderer to make sure everything's lining up properly. My problem is the Sprite and Body at first overlap perfectly, but as I turn the Body moves a bit off the sprite then comes back when the Car is facing either North or South. Here's an image of what I mean: (Not sure what that line is, first time to show up) BLUE is the Body, RED is the Sprite, PURPLE is the Box2DDebugRenderer. Also, you probably noticed a purple square in the top right corner. Well that's the Car drawn by the Box2D Debug Renderer. I thought it might be the camera but I've been playing with the Cameras for hours and nothing seems to work. All give me weird results. Here's my code: Screen: public void show() { // --------------------- SETUP ALL THE CAMERA STUFF ------------------------------ // battleStage = new Stage( 720, 480, false ); // Setup the camera. In Box2D we operate on a meter scale, pixels won't do it. So we use // an Orthographic camera with a Viewport of 24 meters in width and 16 meters in height. battleStage.setCamera( new OrthographicCamera( CAM_METER_WIDTH, CAM_METER_HEIGHT ) ); battleStage.getCamera().position.set( CAM_METER_WIDTH / 2, CAM_METER_HEIGHT / 2, 0 ); // The Box2D Debug Renderer will handle rendering all physics objects for debugging debugger = new Box2DDebugRenderer( true, true, true, true ); //debugCam = new OrthographicCamera( CAM_METER_WIDTH, CAM_METER_HEIGHT ); } public void render(float delta) { // Update the Physics World, use 1/45 for something around 45 Frames/Second for mobile devices physicsWorld.step( 1/45.0f, 8, 3 ); // 1/45 for devices // Set the Camera matrices and clear the screen Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); battleStage.getCamera().update(); // Draw game objects here battleStage.act(delta); battleStage.draw(); // Again update the Camera matrices and call the debug renderer debugCam.update(); debugger.render( physicsWorld, debugCam.combined); // Vehicle handles its own interaction with the HUD // update all Actors movements in the game Stage hudStage.act( delta ); // Draw each Actor onto the Scene at their new positions hudStage.draw(); } Car: (extends Actor) public Car( Texture texture, float posX, float posY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( WIDTH * Consts.PIXEL_METER_RATIO, HEIGHT * Consts.PIXEL_METER_RATIO ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); // set the origin to be at the center of the body mSprite.setPosition( posX * Consts.PIXEL_METER_RATIO, posY * Consts.PIXEL_METER_RATIO ); // place the car in the center of the game map FixtureDef carFixtureDef = new FixtureDef(); mBody = Physics.createBoxBody( BodyType.DynamicBody, carFixtureDef, mSprite ); } public void draw() { mSprite.setPosition( mBody.getPosition().x * Consts.PIXEL_METER_RATIO, mBody.getPosition().y * Consts.PIXEL_METER_RATIO ); mSprite.setRotation( MathUtils.radiansToDegrees * mBody.getAngle() ); // draw the sprite mSprite.draw( batch ); } Physics: (Create the Body) public static Body createBoxBody( final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; boxBodyDef.position.x = pSprite.getX() / Consts.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Consts.PIXEL_METER_RATIO; // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Consts.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Consts.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = BattleScreen.getPhysicsWorld().createBody(boxBodyDef); boxBody.createFixture(pFixtureDef); } Sorry for all the code and long description but it's hard to pin down what exactly might be causing the problem.

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• How to raycast select a scaled OBB?

  - by user3254944

  I have the OBB picking code to select an OBB with code inspired from Real time Rendering 3 and opengl-tutorial.org. I can successfully select objects that have been moved or rotated. However, I cant correctly select an object that has been scaled. The bounding box scales right, but the I can only select the object in a thin strip on its center. How do I fix the checkForHits() function to allow it to read the scaling that I passed to it in the raycast matrix? void GLWidget::selectObjRaycast() { glm::vec2 mouse = (glm::vec2(mousePos.x(), mousePos.y()) / glm::vec2(this->width(), this->height())) * 2.0f - 1.0f; mouse.y *= -1; glm::mat4 toWorld = glm::inverse(ProjectionM * ViewM); glm::vec4 from = toWorld * glm::vec4(mouse, -1.0f, 1.0f); glm::vec4 to = toWorld * glm::vec4(mouse, 1.0f, 1.0f); from /= from.w; to /= to.w; fromAABB = glm::vec3(from); toAABB = glm::normalize(glm::vec3(to - from)); checkForHits(); } void GLWidget::checkForHits() { for (int i = 0; i < myWin.myEtc->allObj.size(); ++i) //check for hits on each obj's bb { bool miss = 0; float tMin = 0.0f; float tMax = 100000.0f; glm::vec3 bbPos(myWin.myEtc->allObj[i]->raycastM[3].x, myWin.myEtc->allObj[i]->raycastM[3].y, myWin.myEtc->allObj[i]->raycastM[3].z); glm::vec3 delta = bbPos - fromAABB; for (int j = 0; j < 3; ++j) { glm::vec3 axis(myWin.myEtc->allObj[i]->raycastM[j].x, myWin.myEtc->allObj[i]->raycastM[j].y, myWin.myEtc->allObj[i]->raycastM[j].z); float e = glm::dot(axis, delta); float f = glm::dot(toAABB, axis); if (fabs(f) > 0.001f) { float t1 = (e + myWin.myEtc->allObj[i]->bbMin[j]) / f; float t2 = (e + myWin.myEtc->allObj[i]->bbMax[j]) / f; if (t1 > t2) { float w = t1; t1 = t2; t2 = w; } if (t2 < tMax) tMax = t2; if (t1 > tMin) tMin = t1; if (tMax < tMin) miss = 1; } else { if (-e + myWin.myEtc->allObj[i]->bbMin[j] > 0.0f || -e + myWin.myEtc->allObj[i]->bbMax[j] < 0.0f) miss = 1; } } if (miss == 0) { intersection_distance = tMin; myWin.myEtc->sel.push_back(myWin.myEtc->allObj[i]); myWin.myEtc->allObj[i]->highlight = myWin.myGLHelp->highlight; break; } } } void Object::render(glm::mat4 PV) { scaleM = glm::scale(glm::mat4(), s->val_3); r_quat = glm::quat(glm::radians(r->val_3)); rotationM = glm::toMat4(r_quat); translationM = glm::translate(glm::mat4(), t->val_3); transLocal1M = glm::translate(glm::mat4(), -rsPivot->val_3); transLocal2M = glm::translate(glm::mat4(), rsPivot->val_3); raycastM = translationM * transLocal2M * rotationM * scaleM * transLocal1M; // MVP = PV * translationM * transLocal2M * rotationM * scaleM * transLocal1M; }

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• Best depth sorting method for a Top Down 2D game using a 3D physics engine

  - by Alic44

  I've spent many days googling this and still have issues with my game engine I'd like to ask about, which I haven't seen addressed before. I think the problem is that my game is an unusual combination of a completely 2D graphical approach using XNA's SpriteBatch, and a completely 3D engine (the amazing BEPU physics engine) with rotation mostly disabled. In essence, my question is similar to this one (the part about "faux 3D"), but the difference is that in my game, the player as well as every other creature is represented by 3D objects, and they can all jump, pick up other objects, and throw them around. What this means is that sorting by one value, such as a Z position (how far north/south a character is on the screen) won't work, because as soon as a smaller creature jumps on top of a larger creature, or a box, and walks backwards, the moment its z value is less than that other creature, it will appear to be behind the object it is actually standing on. I actually originally solved this problem by splitting every object in the game into physics boxes which MUST have a Y height equal to their Z depth. I then based the depth sorting value on the object's y position (how high it is off the ground) PLUS its z position (how far north or south it is on the screen). The problem with this approach is that it requires all moving objects in the game to be split graphically into chunks which match up with a physical box which has its y dimension equal to its z dimension. Which is stupid. So, I got inspired last night to rewrite with a fresh approach. My new method is a little more complex, but I think a little more sane: every object which needs to be sorted by depth in the game exposes the interface IDepthDrawable and is added to a list owned by the DepthDrawer object. IDepthDrawable contains: public interface IDepthDrawable { Rectangle Bounds { get; } //possibly change this to a class if struct copying of the xna Rectangle type becomes an issue DepthDrawShape DepthShape { get; } void Draw(SpriteBatch spriteBatch); } The Bounds Rectangle of each IDepthDrawable object represents the 2D Axis-Aligned Bounding Box it will take up when drawn to the screen. Anything that doesn't intersect the screen will be culled at this stage and the remaining on-screen IDepthDrawables will be Bounds tested for intersections with each other. This is where I get a little less sure of what I'm doing. Each group of collisions will be added to a list or other collection, and each list will sort itself based on its DepthShape property, which will have access to the object-to-be-drawn's physics information. For starting out, lets assume everything in the game is an axis aligned 3D Box shape. Boxes are pretty easy to sort. Something like: if (depthShape1.Back > depthShape2.Front) //if depthShape1 is in front of depthShape2. //depthShape1 goes on top. else if (depthShape1.Bottom > depthShape2.Top) //if depthShape1 is above depthShape2. //depthShape1 goes on top. //if neither of these are true, depthShape2 must be in front or above. So, by sorting draw order by several different factors from the physics engine, I believe I can get a really correct draw order. My question is, is this a good way of going about this, or is there some tried and true, tested way which is completely different and has somehow completely eluded me on the internets? And, if this does seem like a good way to remake my draw order sorting, what's the right sorting algorithm for reordering the Bounds Rectangle collision lists, and how do you deal with a Bounds Rectangle colliding with two different object which don't collide with eachother. I know these are solved problems, but I've only been programming for a year so any specific input here will be greatly appreciated. Thanks for reading this far, ye who made it -- sorry it was so long!

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• Shadows shimmer when camera moves

  - by Chad Layton

  I've implemented shadow maps in my simple block engine as an exercise. I'm using one directional light and using the view volume to create the shadow matrices. I'm experiencing some problems with the shadows shimmering when the camera moves and I'd like to know if it's an issue with my implementation or just an issue with basic/naive shadow mapping itself. Here's a video: http://www.youtube.com/watch?v=vyprATt5BBg&feature=youtu.be Here's the code I use to create the shadow matrices. The commented out code is my original attempt to perfectly fit the view frustum. You can also see my attempt to try clamping movement to texels in the shadow map which didn't seem to make any difference. Then I tried using a bounding sphere instead, also to no apparent effect. public void CreateViewProjectionTransformsToFit(Camera camera, out Matrix viewTransform, out Matrix projectionTransform, out Vector3 position) { BoundingSphere cameraViewFrustumBoundingSphere = BoundingSphere.CreateFromFrustum(camera.ViewFrustum); float lightNearPlaneDistance = 1.0f; Vector3 lookAt = cameraViewFrustumBoundingSphere.Center; float distanceFromLookAt = cameraViewFrustumBoundingSphere.Radius + lightNearPlaneDistance; Vector3 directionFromLookAt = -Direction * distanceFromLookAt; position = lookAt + directionFromLookAt; viewTransform = Matrix.CreateLookAt(position, lookAt, Vector3.Up); float lightFarPlaneDistance = distanceFromLookAt + cameraViewFrustumBoundingSphere.Radius; float diameter = cameraViewFrustumBoundingSphere.Radius * 2.0f; Matrix.CreateOrthographic(diameter, diameter, lightNearPlaneDistance, lightFarPlaneDistance, out projectionTransform); //Vector3 cameraViewFrustumCentroid = camera.ViewFrustum.GetCentroid(); //position = cameraViewFrustumCentroid - (Direction * (camera.FarPlaneDistance - camera.NearPlaneDistance)); //viewTransform = Matrix.CreateLookAt(position, cameraViewFrustumCentroid, Up); //Vector3[] cameraViewFrustumCornersWS = camera.ViewFrustum.GetCorners(); //Vector3[] cameraViewFrustumCornersLS = new Vector3[8]; //Vector3.Transform(cameraViewFrustumCornersWS, ref viewTransform, cameraViewFrustumCornersLS); //Vector3 min = cameraViewFrustumCornersLS[0]; //Vector3 max = cameraViewFrustumCornersLS[0]; //for (int i = 1; i < 8; i++) //{ // min = Vector3.Min(min, cameraViewFrustumCornersLS[i]); // max = Vector3.Max(max, cameraViewFrustumCornersLS[i]); //} //// Clamp to nearest texel //float texelSize = 1.0f / Renderer.ShadowMapSize; //min.X -= min.X % texelSize; //min.Y -= min.Y % texelSize; //min.Z -= min.Z % texelSize; //max.X -= max.X % texelSize; //max.Y -= max.Y % texelSize; //max.Z -= max.Z % texelSize; //// We just use an orthographic projection matrix. The sun is so far away that it's rays are essentially parallel. //Matrix.CreateOrthographicOffCenter(min.X, max.X, min.Y, max.Y, -max.Z, -min.Z, out projectionTransform); } And here's the relevant part of the shader: if (CastShadows) { float4 positionLightCS = mul(float4(position, 1.0f), LightViewProj); float2 texCoord = clipSpaceToScreen(positionLightCS) + 0.5f / ShadowMapSize; float shadowMapDepth = tex2D(ShadowMapSampler, texCoord).r; float distanceToLight = length(LightPosition - position); float bias = 0.2f; if (shadowMapDepth < (distanceToLight - bias)) { return float4(0.0f, 0.0f, 0.0f, 0.0f); } } The shimmer is slightly better if I drastically reduce the view volume but I think that's mostly just because the texels become smaller and it's harder to notice them flickering back and forth. I'd appreciate any insight, I'd very much like to understand what's going on before I try other techniques.

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• Circle-Line Collision Detection Problem

  - by jazzdawg

  I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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• CGContextDrawPDFPage taking up large amounts of memory

  - by Ed Marty

  I have a PDF file that I want to draw in outline form. I want to draw the first several pages on the document each in their own UIImage to use on a button so that when clicked, the main display will navigate to the clicked page. However, CGContextDrawPDFPage seems to be using copious amounts of memory when attempting to draw the page. Even though the image is only supposed to be around 100px tall, the application crashes while drawing one page in particular, which according to Instruments, allocates about 13 MB of memory just for the one page. Here's the code for drawing: //Note: This is always called in a background thread, but the autorelease pool is setup elsewhere + (void) drawPage:(CGPDFPageRef)m_page inRect:(CGRect)rect inContext:(CGContextRef) g { CGPDFBox box = kCGPDFMediaBox; CGAffineTransform t = CGPDFPageGetDrawingTransform(m_page, box, rect, 0,YES); CGRect pageRect = CGPDFPageGetBoxRect(m_page, box); //Start the drawing CGContextSaveGState(g); //Clip to our bounding box CGContextClipToRect(g, pageRect); //Now we have to flip the origin to top-left instead of bottom left //First: flip y-axix CGContextScaleCTM(g, 1, -1); //Second: move origin CGContextTranslateCTM(g, 0, -rect.size.height); //Now apply the transform to draw the page within the rect CGContextConcatCTM(g, t); //Finally, draw the page //The important bit. Commenting out the following line "fixes" the crashing issue. CGContextDrawPDFPage(g, m_page); CGContextRestoreGState(g); } Is there a better way to draw this image that doesn't take up huge amounts of memory?

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• Mimic CALayer shadow properties found in iPhone OS 3.2 for OS 3.1

  - by niblha

  The CALayer shadow properties like shadowOffset, shadowRadius, shadowColor are not available in iPhone OS versions below 3.2 and I'm wondering how I could mimic that functionality for use with 3.1 and below. I want to use this to be able to add drop shadows to UIViews in a clean way so that the shadows are drawn at layer level somehow, and not by drawing it in a view's -(void)drawRect:(CGRect)rect method which requires to shrink the actual views frame to accomodate for the shadow. (This shrinking approach have been proposed in the other UIView drop shadow related questions I found here on SO). I was thinking a layered approach would be cleaner. For example I tried creating subclassing CALayer to which I added a separate shadow layer as a sublayer, but then that would be drawn on top of whatever was draw in the drawRect: method of the UIView that had the main layer as backing layer. I've also tried implementing the subclass CALayer's drawInContext: something like this, - (void)drawInContext:(CGContextRef)ctx { // code to draw shadow for a frame the size of the layer's frame [super drawInContext:ctx]; } But then the shadow is still clipped to the current clipping bounding box of the context, which seems to be the layers own frame. I also had some idea of redirecting the drawing of the main layer to a sublayer, which would be placed above another sublayer which had the shadow drawn onto it. Then I would probably get rid of the clipping and the shadow would be farthest away. But I couldn't really wrap my head around how I would do that, and it doesn't really feel like a clean approach. Any ideas on how to go about this? Just to make clear how my UIView drop shadow related question is different from the other ones I found here on SO; I do not want to shrink the actual drawing frame of a UIView to accomodate for a shadow. I want it to somehow be on a separate layer in the background, whithout beeing clipped.

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