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  • Fast pixelshader 2D raytracing

    - by heishe
    I'd like to do a simple 2D shadow calculation algorithm by rendering my environment into a texture, and then use raytracing to determine what pixels of the texture are not visible to the point light (simply handed to the shader as a vec2 position) . A simple brute force algorithm per pixel would looks like this: line_segment = line segment between current pixel of texture and light source For each pixel in the texture: { if pixel is not just empty space && pixel is on line_segment output = black else output = normal color of the pixel } This is, of course, probably not the fastest way to do it. Question is: What are faster ways to do it or what are some optimizations that can be applied to this technique?

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  • XNA - Finding boundaries in isometric tilemap

    - by Yheeky
    I have an issue with my 2D isometric engine. I'm using my own 2D camera class which works with matrices and need to find the tilemaps boundaries so the user always sees the map. Currently my map size is 100x100 (with 128x128 tiles) so the calculation (e.g. for the right boundary) is: var maxX = (TileMap.MapWidth + 1) * (TileMap.TileWidth / 2) - ViewSize.X; var maxX = (100 + 1) * (128 / 2) - 1360; // = 5104 pixels. This works fine while having scale factor of 1.0f but not for any other zoom factor. When I zoom out to 0.9f the right border should be at approx. 4954. I´m using the following code for transformation but I always get a wrong value: var maxXVector = new Vector2(maxX, 0); var maxXTransformed = Vector2.Transform(maxXVector, tempTransform).X; The result is 4593. Does anyone of you have an idea what I´m during wrong? Thanks for your help! Yheeky

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  • Multiple volumetric lights

    - by notabene
    I recently read this GPU GEMS 3 article Volumetric Light Scattering as a Post-Process. I like the idea to add volumetric light property to realtime render i'm working on. Question is will it work for multiple lights? Our renderer uses one render pass per light and uses additive blending to sum incoming light. I'm mostly convinced that it have to work nice. Do you agree? Maybe there can be problem where light rays crosses each other.

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  • Reasoner Conversion Problems:

    - by Annalyne
    I have this code right here in Java and I wanted to translate it in C++, but I had some problems going: this is the java code: import java.io.*; import java.util.*; public class ClueReasoner { private int numPlayers; private int playerNum; private int numCards; private SATSolver solver; private String caseFile = "cf"; private String[] players = {"sc", "mu", "wh", "gr", "pe", "pl"}; private String[] suspects = {"mu", "pl", "gr", "pe", "sc", "wh"}; private String[] weapons = {"kn", "ca", "re", "ro", "pi", "wr"}; private String[] rooms = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; private String[] cards; public ClueReasoner() { numPlayers = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; numCards = i; // Initialize solver solver = new SATSolver(); addInitialClauses(); } private int getPlayerNum(String player) { if (player.equals(caseFile)) return numPlayers; for (int i = 0; i < numPlayers; i++) if (player.equals(players[i])) return i; System.out.println("Illegal player: " + player); return -1; } private int getCardNum(String card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; System.out.println("Illegal card: " + card); return -1; } private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); } private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; } public void addInitialClauses() { // TO BE IMPLEMENTED AS AN EXERCISE // Each card is in at least one place (including case file). for (int c = 0; c < numCards; c++) { int[] clause = new int[numPlayers + 1]; for (int p = 0; p <= numPlayers; p++) clause[p] = getPairNum(p, c); solver.addClause(clause); } // If a card is one place, it cannot be in another place. // At least one card of each category is in the case file. // No two cards in each category can both be in the case file. } public void hand(String player, String[] cards) { playerNum = getPlayerNum(player); // TO BE IMPLEMENTED AS AN EXERCISE } public void suggest(String suggester, String card1, String card2, String card3, String refuter, String cardShown) { // TO BE IMPLEMENTED AS AN EXERCISE } public void accuse(String accuser, String card1, String card2, String card3, boolean isCorrect) { // TO BE IMPLEMENTED AS AN EXERCISE } public int query(String player, String card) { return solver.testLiteral(getPairNum(player, card)); } public String queryString(int returnCode) { if (returnCode == SATSolver.TRUE) return "Y"; else if (returnCode == SATSolver.FALSE) return "n"; else return "-"; } public void printNotepad() { PrintStream out = System.out; for (String player : players) out.print("\t" + player); out.println("\t" + caseFile); for (String card : cards) { out.print(card + "\t"); for (String player : players) out.print(queryString(query(player, card)) + "\t"); out.println(queryString(query(caseFile, card))); } } public static void main(String[] args) { ClueReasoner cr = new ClueReasoner(); String[] myCards = {"wh", "li", "st"}; cr.hand("sc", myCards); cr.suggest("sc", "sc", "ro", "lo", "mu", "sc"); cr.suggest("mu", "pe", "pi", "di", "pe", null); cr.suggest("wh", "mu", "re", "ba", "pe", null); cr.suggest("gr", "wh", "kn", "ba", "pl", null); cr.suggest("pe", "gr", "ca", "di", "wh", null); cr.suggest("pl", "wh", "wr", "st", "sc", "wh"); cr.suggest("sc", "pl", "ro", "co", "mu", "pl"); cr.suggest("mu", "pe", "ro", "ba", "wh", null); cr.suggest("wh", "mu", "ca", "st", "gr", null); cr.suggest("gr", "pe", "kn", "di", "pe", null); cr.suggest("pe", "mu", "pi", "di", "pl", null); cr.suggest("pl", "gr", "kn", "co", "wh", null); cr.suggest("sc", "pe", "kn", "lo", "mu", "lo"); cr.suggest("mu", "pe", "kn", "di", "wh", null); cr.suggest("wh", "pe", "wr", "ha", "gr", null); cr.suggest("gr", "wh", "pi", "co", "pl", null); cr.suggest("pe", "sc", "pi", "ha", "mu", null); cr.suggest("pl", "pe", "pi", "ba", null, null); cr.suggest("sc", "wh", "pi", "ha", "pe", "ha"); cr.suggest("wh", "pe", "pi", "ha", "pe", null); cr.suggest("pe", "pe", "pi", "ha", null, null); cr.suggest("sc", "gr", "pi", "st", "wh", "gr"); cr.suggest("mu", "pe", "pi", "ba", "pl", null); cr.suggest("wh", "pe", "pi", "st", "sc", "st"); cr.suggest("gr", "wh", "pi", "st", "sc", "wh"); cr.suggest("pe", "wh", "pi", "st", "sc", "wh"); cr.suggest("pl", "pe", "pi", "ki", "gr", null); cr.printNotepad(); cr.accuse("sc", "pe", "pi", "bi", true); } } how can I convert this? there are too many errors I get. for my C++ code (as a commentor asked for) #include <iostream> #include <cstdlib> #include <string> using namespace std; void Scene_Reasoner() { int numPlayer; int playerNum; int cardNum; string filecase = "Case: "; string players [] = {"sc", "mu", "wh", "gr", "pe", "pl"}; string suspects [] = {"mu", "pl", "gr", "pe", "sc", "wh"}; string weapons [] = {"kn", "ca", "re", "ro", "pi", "wr"}; string rooms[] = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; string cards [0]; }; void Scene_Reason_Base () { numPlayer = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; cardNum = i; }; private int getCardNum (string card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; cout << "Illegal card: " + card <<endl; return -1; }; private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); }; private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; }; int main () { return 0; }

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  • Best practices with Vertices in Open GL

    - by Darestium
    What is the best practice in regards to storing vertex data in Open GL? I.e: struct VertexColored { public: GLfloat position[]; GLfloat normal[]; byte colours[]; } class Terrian { private: GLuint vbo_vertices; GLuint vbo_normals; GLuint vbo_colors; GLuint ibo_elements; VertexColored vertices[]; } or having them stored seperatly in the required class like: class Terrian { private: GLfloat vertices[]; GLfloat normals[]; GLfloat colors[]; GLuint vbo_vertices; GLuint vbo_normals; GLuint vbo_colors; GLuint ibo_elements; }

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  • 3d vertex translated onto 2d viewport

    - by Dan Leidal
    I have a spherical world defined by simple trigonometric functions to create triangles that are relatively similar in size and shape throughout. What I want to be able to do is use mouse input to target a range of vertices in the area around the mouse click in order to manipulate these vertices in real time. I read a post on this forum regarding translating 3d world coordinates into the 2d viewport.. it recommended that you should multiply the world vector coordinates by the viewport and then the projection, but they didn't include any code examples, and suffice to say i couldn't get any good results. Further information.. I am using a lookat method for the viewport. Does this cause a problem, and if so is there a solution? If this isn't the problem, does anyone have a simple code example illustrating translating one vertex in a 3d world into a 2d viewspace? I am using XNA.

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  • Audio Panning using RtAudio

    - by user1801724
    I use Rtaudio library. I would like to implement an audio program where I can control the panning (e.g. shifting the sound from the left channel to the right channel). In my specific case, I use a duplex mode (you can find an example here: duplex mode). It means that I link the microphone input to the speaker output. I seek on the web, but I did not find anything useful. Should I apply a filter on the output buffer? What kind of filter? Can anyone help me? Thanks

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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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  • Box2D physics editor for complex bodies

    - by Paul Manta
    Is there any editor out there that would allow me to define complex entities, with joins connecting their multiple bodies, instead of regular single body entities? For example, an editor that would allow me to 'define' a car as having a main body with two circles as wheels, connected through joints. Clarification: I realize I haven't been clear enough about what I need. I'd like to make my engine data-driven, so all entities (and therefore their Box2D bodies) should be defined externally, not in code. I'm looking for a program like Code 'N' Web's PhysicsEditor, except that one only handles single body entities, no joints or anything like that. Like PhysicsEditor, the program should be configurable so that I can save the data in whatever format I want to. Does anyone know of any such software?

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  • Looking for a good actionscript 3 book

    - by Jari Komppa
    I've been looking for a book on actionscript3 development, but while there's tons of books out there, nobody seems to want to recommend any specific one. One book I've been pointed towards is the cookbook by o'reilly, but it, like most books out there, seems to be based on the assumption that I'm using flexbuilder or flash. Instead, I'm "just" using flashdevelop, or the free SDK directly. I've also been told to just go with the api reference and live with it. I could do that, I suppose, but I'd rather have a book that gives me the big picture. Kind of like with cocoa, there's the hillegrass' book, or the red book of OpenGL. So, what would be the actionscript3 book out there?

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  • Finding direction of travel in a world with wrapped edges

    - by crazy
    I need to find the shortest distance direction from one point in my 2D world to another point where the edges are wrapped (like asteroids etc). I know how to find the shortest distance but am struggling to find which direction it's in. The shortest distance is given by: int rows = MapY; int cols = MapX; int d1 = abs(S.Y - T.Y); int d2 = abs(S.X - T.X); int dr = min(d1, rows-d1); int dc = min(d2, cols-d2); double dist = sqrt((double)(dr*dr + dc*dc)); Example of the world : : T : :--------------:--------- : : : S : : : : : : T : : : :--------------: In the diagram the edges are shown with : and -. I've shown a wrapped repeat of the world at the top right too. I want to find the direction in degrees from S to T. So the shortest distance is to the top right repeat of T. but how do I calculate the direction in degreed from S to the repeated T in the top right? I know the positions of both S and T but I suppose I need to find the position of the repeated T however there more than 1. The worlds coordinates system starts at 0,0 at the top left and 0 degrees for the direction could start at West. It seems like this shouldn’t be too hard but I haven’t been able to work out a solution. I hope somone can help? Any websites would be appreciated.

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  • Correct Rotation and Translation with a 4x4 matrix

    - by sFuller
    I am using a 4x4 matrix to transform verts in a shader. I multiply an identity matrix by a rotation matrix by a translation matrix. I am trying to first rotate the verts and then translate them, however in my result, it appears that the verts are being transformed and then rotated. My matrix looks something like this: m00 m01 m02 tx m10 m11 m12 ty m20 m21 m22 tz --- --- --- 1 I am not using OpenGL's fixed function pipeline, I am multiplying matrices on the client side, and uploading the matrix to a GLSL shader. If it helps, I am using my own matrix multiplication code, but I have recreated this problem using matrices on my graphing calculator, so I don't believe my matrix code has errors.. I'll include a visual aid if needed.

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  • Fitting a rectangle into screen with XNA

    - by alecnash
    I am drawing a rectangle with primitives in XNA. The width is: width = GraphicsDevice.Viewport.Width and the height is height = GraphicsDevice.Viewport.Height I am trying to fit this rectangle in the screen (using different screens and devices) but I am not sure where to put the camera on the Z-axis. Sometimes the camera is too close and sometimes to far. This is what I am using to get the camera distance: //Height of piramid float alpha = 0; float beta = 0; float gamma = 0; alpha = (float)Math.Sqrt((width / 2 * width/2) + (height / 2 * height / 2)); beta = height / ((float)Math.Cos(MathHelper.ToRadians(67.5f)) * 2); gamma = (float)Math.Sqrt(beta*beta - alpha*alpha); position = new Vector3(0, 0, gamma); Any idea where to put the camera on the Z-axis?

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  • 2D object-aligned bounding-box intersection test

    - by AshleysBrain
    Hi all, I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding box test to quickly discard distant objects, so it doesn't matter if the quad routine is a little slower.) My boxes are stored as four x,y points. I've searched around for answers, but I can't make sense of the variable names and algorithms in examples to apply them to my particular case. Can someone help show me how this would be done, in a clear and simple way? Thanks. (The particular language isn't important, C-style pseudo code is OK.)

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  • Any reliable polygon normal calculation code?

    - by Jenko
    I'm currently calculating the normal vector of a polygon using this code, but for some faces here and there it calculates a wrong normal. I don't really know what's going on or where it fails but its not reliable. Do you have any polygon normal calculation that's tested and found to be reliable? // calculate normal of a polygon using all points var n:int = points.length; var x:Number = 0; var y:Number = 0; var z:Number = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // turn large values into a unit vector if (length != 0){ x = x / length; y = y / length; z = z / length; }else { throw new Error("Cannot calculate normal since triangle has an area of 0"); }

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  • Why am I not getting an sRGB default framebuffer?

    - by Aaron Rotenberg
    I'm trying to make my OpenGL Haskell program gamma correct by making appropriate use of sRGB framebuffers and textures, but I'm running into issues making the default framebuffer sRGB. Consider the following Haskell program, compiled for 32-bit Windows using GHC and linked against 32-bit freeglut: import Foreign.Marshal.Alloc(alloca) import Foreign.Ptr(Ptr) import Foreign.Storable(Storable, peek) import Graphics.Rendering.OpenGL.Raw import qualified Graphics.UI.GLUT as GLUT import Graphics.UI.GLUT(($=)) main :: IO () main = do (_progName, _args) <- GLUT.getArgsAndInitialize GLUT.initialDisplayMode $= [GLUT.SRGBMode] _window <- GLUT.createWindow "sRGB Test" -- To prove that I actually have freeglut working correctly. -- This will fail at runtime under classic GLUT. GLUT.closeCallback $= Just (return ()) glEnable gl_FRAMEBUFFER_SRGB colorEncoding <- allocaOut $ glGetFramebufferAttachmentParameteriv gl_FRAMEBUFFER gl_FRONT_LEFT gl_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING print colorEncoding allocaOut :: Storable a => (Ptr a -> IO b) -> IO a allocaOut f = alloca $ \ptr -> do f ptr peek ptr On my desktop (Windows 8 64-bit with a GeForce GTX 760 graphics card) this program outputs 9729, a.k.a. gl_LINEAR, indicating that the default framebuffer is using linear color space, even though I explicitly requested an sRGB window. This is reflected in the rendering results of the actual program I'm trying to write - everything looks washed out because my linear color values aren't being converted to sRGB before being written to the framebuffer. On the other hand, on my laptop (Windows 7 64-bit with an Intel graphics chip), the program prints 0 (huh?) and I get an sRGB default framebuffer by default whether I request one or not! And on both machines, if I manually create a non-default framebuffer bound to an sRGB texture, the program correctly prints 35904, a.k.a. gl_SRGB. Why am I getting different results on different hardware? Am I doing something wrong? How can I get an sRGB framebuffer consistently on all hardware and target OSes?

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  • Pathfinding in multi goal, multi agent environment

    - by Rohan Agrawal
    I have an environment in which I have multiple agents (a), multiple goals (g) and obstacles (o). . . . a o . . . . . . . o . g . . a . . . . . . . . . . o . . . . o o o o . g . . o . . . . . . . o . . . . o . . . . o o o o a What would an appropriate algorithm for pathfinding in this environment? The only thing I can think of right now, is to Run a separate version of A* for each goal separately, but i don't think that's very efficient.

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  • Drawing isometric map in canvas / javascript

    - by Dave
    I have a problem with my map design for my tiles. I set player position which is meant to be the middle tile that the canvas is looking at. How ever the calculation to put them in x:y pixel location is completely messed up for me and i don't know how to fix it. This is what i tried: var offset_x = 0; //used for scrolling on x var offset_y = 0; //used for scrolling on y var prev_mousex = 0; //for movePos function var prev_mousey = 0; //for movePos function function movePos(e){ if (prev_mousex === 0 && prev_mousey === 0) { prev_mousex = e.pageX; prev_mousey = e.pageY; } offset_x = offset_x + (e.pageX - prev_mousex); offset_y = offset_y + (e.pageY - prev_mousey); prev_mousex = e.pageX; prev_mousey = e.pageY; run = true; } player_posx = 5; player_posy = 55; ct = 19; for (i = (player_posx-ct); i < (player_posx+ct); i++){ //horizontal for (j=(player_posy-ct); j < (player_posy+ct); j++){ // vertical //img[0] is 64by64 but the graphic is 64by32 the rest is alpha space var x = (i-j)*(img[0].height/2) + (canvas.width/2)-(img[0].width/2); var y = (i+j)*(img[0].height/4); var abposx = x - offset_x; var abposy = y - offset_y; ctx.drawImage(img[0],abposx,abposy); } } Now based on these numbers the first render-able tile is I = 0 & J = 36. As numbers in the negative are not in the array. But for I=0 and J= 36 the position it calculates is : -1120 : 592 Does any one know how to center it to canvas view properly?

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  • Light shaped like a line

    - by Michael
    I am trying to figure out how line-shaped lights fit into the standard point light/spotlight/directional light scheme. The way I see it, there are two options: Seed the line with regular point lights and just deal with the artifacts. Easy, but seems wasteful. Make the line some kind of emissive material and apply a bloom effect. Sounds like it could work, but I can't test it in my engine yet. Is there a standard way to do this? Or for non-point lights in general?

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  • matrix 4x4 position data

    - by freefallr
    I understand that a 4x4 matrix holds rotation and position data. The rotation data is held in the 3x3 sub-matrix at the top left of the matrix. The position data is held in the last column of the matrix. e.g. glm::vec3 vParentPos( mParent[3][0], mParent[3][1], mParent[3][2] ); My question is - am I accessing the parent matrix correctly in the example above? I know that opengl uses a different matrix ordering that directx, (row order instead of column order or something), so, should the mParent be accessed as follows instead? glm::vec3 vParentPos( mParent[0][3], mParent[1][3], mParent[2][3] ); thanks!

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  • Camera closes in on the fixed point

    - by V1ncam
    I've been trying to create a camera that is controlled by the mouse and rotates around a fixed point (read: (0,0,0)), both vertical and horizontal. This is what I've come up with: camera.Eye = Vector3.Transform(camera.Eye, Matrix.CreateRotationY(camRotYFloat)); Vector3 customAxis = new Vector3(-camera.Eye.Z, 0, camera.Eye.X); camera.Eye = Vector3.Transform(camera.Eye, Matrix.CreateFromAxisAngle(customAxis, camRotXFloat * 0.0001f)); This works quit well, except from the fact that when I 'use' the second transformation (go up and down with the mouse) the camera not only goes up and down, it also closes in on the point. It zooms in. How do I prevent this? Thanks in advance.

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  • Modern Shader Book?

    - by Michael Stum
    I'm interested in learning about Shaders: What are they, when/for what would I use them, and how to use them. (Specifically I'm interested in Water and Bloom effects, but I know close to 0 about Shaders, so I need a general introduction). I saw a lot of books that are a couple of years old, so I don't know if they still apply. I'm targeting XNA 4.0 at the moment (which I believe means HLSL Shaders for Shader Model 4.0), but anything that generally targets DirectX 11 and OpenGL 4 is helpful I guess.

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  • Light following me around the room. Something is wrong with my shader!

    - by Robinson
    I'm trying to do a spot (Blinn) light, with falloff and attenuation. It seems to be working OK except I have a bit of a space problem. That is, whenever I move the camera the light moves to maintain the same relative position, rather than changing with the camera. This results in the light moving around, i.e. not always falling on the same surfaces. It's as if there's a flashlight attached to the camera. I'm transforming the lights beforehand into view space, so Light_Position and Light_Direction are already in eye space (I hope!). I made a little movie of what it looks like here: My camera rotating around a point inside a box. The light is fixed in the centre up and its "look at" point in a fixed position in front of it. As you can see, as the camera rotates around the origin (always looking at the centre), so don't think the box is rotating (!). The lighting follows it around. To start, some code. This is how I'm transforming the light into view space (it gets passed into the shader already in view space): // Compute eye-space light position. Math::Vector3d eyeSpacePosition = MyCamera->ViewMatrix() * MyLightPosition; MyShaderVariables->Set(MyLightPositionIndex, eyeSpacePosition); // Compute eye-space light direction vector. Math::Vector3d eyeSpaceDirection = Math::Unit(MyLightLookAt - MyLightPosition); MyCamera->ViewMatrixInverseTranspose().TransformNormal(eyeSpaceDirection); MyShaderVariables->Set(MyLightDirectionIndex, eyeSpaceDirection); Can anyone give me a clue as to what I'm doing wrong here? I think the light should remain looking at a fixed point on the box, regardless of the camera orientation. Here are the vertex and pixel shaders: /////////////////////////////////////////////////// // Vertex Shader /////////////////////////////////////////////////// #version 420 /////////////////////////////////////////////////// // Uniform Buffer Structures /////////////////////////////////////////////////// // Camera. layout (std140) uniform Camera { mat4 Camera_View; mat4 Camera_ViewInverseTranspose; mat4 Camera_Projection; }; // Matrices per model. layout (std140) uniform Model { mat4 Model_World; mat4 Model_WorldView; mat4 Model_WorldViewInverseTranspose; mat4 Model_WorldViewProjection; }; // Spotlight. layout (std140) uniform OmniLight { float Light_Intensity; vec3 Light_Position; vec3 Light_Direction; vec4 Light_Ambient_Colour; vec4 Light_Diffuse_Colour; vec4 Light_Specular_Colour; float Light_Attenuation_Min; float Light_Attenuation_Max; float Light_Cone_Min; float Light_Cone_Max; }; /////////////////////////////////////////////////// // Streams (per vertex) /////////////////////////////////////////////////// layout(location = 0) in vec3 attrib_Position; layout(location = 1) in vec3 attrib_Normal; layout(location = 2) in vec3 attrib_Tangent; layout(location = 3) in vec3 attrib_BiNormal; layout(location = 4) in vec2 attrib_Texture; /////////////////////////////////////////////////// // Output streams (per vertex) /////////////////////////////////////////////////// out vec3 attrib_Fragment_Normal; out vec4 attrib_Fragment_Position; out vec2 attrib_Fragment_Texture; out vec3 attrib_Fragment_Light; out vec3 attrib_Fragment_Eye; /////////////////////////////////////////////////// // Main /////////////////////////////////////////////////// void main() { // Transform normal into eye space attrib_Fragment_Normal = (Model_WorldViewInverseTranspose * vec4(attrib_Normal, 0.0)).xyz; // Transform vertex into eye space (world * view * vertex = eye) vec4 position = Model_WorldView * vec4(attrib_Position, 1.0); // Compute vector from eye space vertex to light (light is in eye space already) attrib_Fragment_Light = Light_Position - position.xyz; // Compute vector from the vertex to the eye (which is now at the origin). attrib_Fragment_Eye = -position.xyz; // Output texture coord. attrib_Fragment_Texture = attrib_Texture; // Compute vertex position by applying camera projection. gl_Position = Camera_Projection * position; } and the pixel shader: /////////////////////////////////////////////////// // Pixel Shader /////////////////////////////////////////////////// #version 420 /////////////////////////////////////////////////// // Samplers /////////////////////////////////////////////////// uniform sampler2D Map_Diffuse; /////////////////////////////////////////////////// // Global Uniforms /////////////////////////////////////////////////// // Material. layout (std140) uniform Material { vec4 Material_Ambient_Colour; vec4 Material_Diffuse_Colour; vec4 Material_Specular_Colour; vec4 Material_Emissive_Colour; float Material_Shininess; float Material_Strength; }; // Spotlight. layout (std140) uniform OmniLight { float Light_Intensity; vec3 Light_Position; vec3 Light_Direction; vec4 Light_Ambient_Colour; vec4 Light_Diffuse_Colour; vec4 Light_Specular_Colour; float Light_Attenuation_Min; float Light_Attenuation_Max; float Light_Cone_Min; float Light_Cone_Max; }; /////////////////////////////////////////////////// // Input streams (per vertex) /////////////////////////////////////////////////// in vec3 attrib_Fragment_Normal; in vec3 attrib_Fragment_Position; in vec2 attrib_Fragment_Texture; in vec3 attrib_Fragment_Light; in vec3 attrib_Fragment_Eye; /////////////////////////////////////////////////// // Result /////////////////////////////////////////////////// out vec4 Out_Colour; /////////////////////////////////////////////////// // Main /////////////////////////////////////////////////// void main(void) { // Compute N dot L. vec3 N = normalize(attrib_Fragment_Normal); vec3 L = normalize(attrib_Fragment_Light); vec3 E = normalize(attrib_Fragment_Eye); vec3 H = normalize(L + E); float NdotL = clamp(dot(L,N), 0.0, 1.0); float NdotH = clamp(dot(N,H), 0.0, 1.0); // Compute ambient term. vec4 ambient = Material_Ambient_Colour * Light_Ambient_Colour; // Diffuse. vec4 diffuse = texture2D(Map_Diffuse, attrib_Fragment_Texture) * Light_Diffuse_Colour * Material_Diffuse_Colour * NdotL; // Specular. float specularIntensity = pow(NdotH, Material_Shininess) * Material_Strength; vec4 specular = Light_Specular_Colour * Material_Specular_Colour * specularIntensity; // Light attenuation (so we don't have to use 1 - x, we step between Max and Min). float d = length(-attrib_Fragment_Light); float attenuation = smoothstep(Light_Attenuation_Max, Light_Attenuation_Min, d); // Adjust attenuation based on light cone. float LdotS = dot(-L, Light_Direction), CosI = Light_Cone_Min - Light_Cone_Max; attenuation *= clamp((LdotS - Light_Cone_Max) / CosI, 0.0, 1.0); // Final colour. Out_Colour = (ambient + diffuse + specular) * Light_Intensity * attenuation; }

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  • Time calculation between openGL update calls.

    - by Vijayendra
    In XNA, the system calls update and draw function with the time information. This contains information such as how much time has passed since last update was called. This makes easy to integrate time and do animation calculation accordingly. But I dont see any such mechanism in openGL. I see openGL requires programmers to have their own implementation which could be buggy or inefficient. Is there any standard (and efficient) code that demonstrate this practice in openGL?

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  • Lighting-Reflectance Models & Licensing Issues

    - by codey
    Generally, or specifically, is there any licensing issue with using any of the well known lighting/reflectance models (i.e. the BRDFs or other distribution or approximation functions): Phong, Blinn–Phong, Cook–Torrance, Blinn-Torrance-Sparrow, Lambert, Minnaert, Oren–Nayar, Ward, Strauss, Ashikhmin-Shirley and common modifications where applicable, such as: Beckmann distribution, Blinn distribution, Schlick's approximation, etc. in your shader code utilised in a commercial product? Or is it a non-issue?

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