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• TGA loader: reverse height

  - by aVoX

  I wrote a TGA image loader in Java which is working perfectly for files created with GIMP as long as they are saved with the option "origin" set to "Top Left" (Note: Actually TGA files are meant to be stored upside down - "Bottom Left" in GIMP). My problem is that I want my image loader to be capable of reading all different kinds of TGAs, so my question is, how do I flip the image upside down? Note that I store all image data inside a one-dimensional byte array, because OpenGL (glTexImage2D to be specific) requires it that way. Thanks in advance.

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• I enabled and setup glBlendFunc, but my texture has a white outline. What am I doing wrong?

  - by vinzBad

  You can see most of my source code in this question: Instead of the specified Texture, black circles on a green background are getting rendered. Why? Now I have the problem, that my texture has a white outline on its transparent parts. After googling and setting up glBlendFunc, the outline just got "softer". This is how it looks like: This is how I now setup OpenGL: public static void SetupGL() { GL.Enable(EnableCap.Blend); GL.BlendFunc(BlendingFactorSrc.SrcAlpha, BlendingFactorDest.OneMinusSrcAlpha); GL.Enable(EnableCap.Texture2D); GL.Hint(HintTarget.PerspectiveCorrectionHint, HintMode.Nicest); }

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• Developing GLSL Shaders?

  - by skln

  I want to create shaders but I need a tool to create and see the visual result before I put them into my game. As to determine if there is something wrong with my game or if it's something with the shader I created. I've looked at some like Render Monkey and OpenGL Shader Designer from what I recall of Render Monkey it had a way to define your own attributes (now as "in" for vertex shaders = 330) easily though I can't remember to what extent. Shader Designer requires a plugin that I didn't even bother to look at creating cause it's an external process and plugin. Are there any tools out there that support a scripting language and I could easily provide specific input such as float movement = sin(elapsedTime()); and then define in float movement; in the vertex shader ? It'd be cool if anyone could share how they develop shaders, if they just code away and then plug it into their game hoping to get the result they wanted.

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• Data structures for storing finger/stylus movements in drawing application?

  - by mattja?øb

  I have a general question about creating a drawing application, the language could be C++ or ObjectiveC with OpenGL. I would like to hear what are the best methods and practices for storing strokes data. Think of the many iPad apps that allow you to draw with your finger (or a stylus) or any other similar function on a desktop app. To summarize, the data structure must: be highly responsive to the movement store precise values (close in space / time) usable for rendering the strokes with complex textures (textures based on the dynamic of the stroke etc) exportable to a text file for saving/loading

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• Should iOS games use a Timer?

  - by ????

  No matter what frameworks we use -- Core Graphics, Cocos2D, OpenGL ES -- to write games, should a timer be used (for games that has animation even when a user doesn't do any input, such as after firing a missile and waiting to see if the UFO is hit)? I read that NSTimer might not get fired until after scheduled time (interval), and CADisplayLink can delay and get fired at a later time as well, only that it tells you how late it is so you can move the object more, so it can make the object look like it skipped frame. Must we use a Timer? And if so, what is the best one to use?

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• Writing a basic shader for large input files

  - by Zoltan Varadi

  I started writing a shader for my iOS app and instead of starting from scratch i used this tutorial here: http://www.raywenderlich.com/3664/opengl-es-2-0-for-iphone-tutorial I wrote an import function, first to import wavefront .obj models. My problem is that with I can't handle larger inputs (with a simple cube it was working). I realized that the indices array is an array of GLubyte values, which is unsigned char, so as a result i cant have more than 256 indexes. I modified it to GLuint, but then only get a blank screen. What else needs to me modified? p.s.: the source can be downloaded from here: http://d1xzuxjlafny7l.cloudfront.net/downloads/HelloOpenGL.zip

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• TGA loader: reverse y-axis

  - by aVoX

  I've written a TGA image loader in Java which is working perfectly for files created with GIMP as long as they are saved with the option origin set to Top Left (Note: Actually TGA files are meant to be stored upside down - Bottom Left in GIMP). My problem is that I want my image loader to be capable of reading all different kinds of TGA, so my question is: How do I flip the image upside down? Note that I store all image data inside a one-dimensional byte array, because OpenGL (glTexImage2D to be specific) requires it that way. Thanks in advance.

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• Using OpenCl to jiggle the Pipe

  - by TOAOGG

  I've got the Idea to use OpenCL to program a simple Renderer. A clear contra is, that this approach won't benefit from the hardware as the functions on the device (I think). Would it be useful to do this in OpenCL..lets say we want to Cull as early as possible so we won't have many per vertex operations. Is it correct, that Culling is done after the Vertex-Shader? For static-vertecies who won't get effected by the shader it could be interesting to cull them before. Another idea would be an deferred renderer. So the main question is: Would it make sense to program a renderer in OpenCL (aside the effort)? The resulting picture would be drawn in OpenGL.

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• What are the semantics of glRotate and glTranslate's parameters?

  - by Zarkopafilis

  I have been trying to play with OpenGL after watching some tutorials and I don't understand how the glTranslatef and glRotatef functions work. I believe a simple picture would help me. I understand that glTranslatef changes the position of the "camera" (but does it change the position in wich the shapes are getting drawn)? However, I don't understand the rotation concept at all. If I do glRotatef(1,0,0,1) it makes my quad spin around. If I just do glRotatef(1,0,0,0) it makes the quad smaller (further away) but if I try to rotate around the X or Y axis, I get a black screen. I don't understand the angle either. Help would be appreciated.

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• In 3D camera math, calculate what Z depth is pixel unity for a given FOV

  - by badweasel

  I am working in iOS and OpenGL ES 2.0. Through trial and error I've figured out a frustum to where at a specific z depth pixels drawn are 1 to 1 with my source textures. So 1 pixel in my texture is 1 pixel on the screen. For 2d games this is good. Of course it means that I also factor in things like the size of the quad and the size of the texture. For example if my sprite is a quad 32x32 pixels. The quad size is 3.2 units wide and tall. And the texcoords are 32 / the size of the texture wide and tall. Then the frustum is: matrixFrustum(-(float)backingWidth/frustumScale,(float)backingWidth/frustumScale, -(float)backingHeight/frustumScale, (float)backingHeight/frustumScale, 40, 1000, mProjection); Where frustumScale is 800 for a retina screen. Then at a distance of 800 from camera the sprite is pixel for pixel the same as photoshop. For 3d games sometimes I still want to be able to do this. But depending on the scene I sometimes need the FOV to be different things. I'm looking for a way to figure out what Z depth will achieve this same pixel unity for a given FOV. For this my mProjection is set using: matrixPerspective(cameraFOV, near, far, (float)backingWidth / (float)backingHeight, mProjection); With testing I found that at an FOV of 45.0 a Z of 38.5 is very close to pixel unity. And at an FOV of 30.0 a Z of 59.5 is about right. But how can I calculate a value that is spot on? Here's my matrixPerspecitve code: void matrixPerspective(float angle, float near, float far, float aspect, mat4 m) { //float size = near * tanf(angle / 360.0 * M_PI); float size = near * tanf(degreesToRadians(angle) / 2.0); float left = -size, right = size, bottom = -size / aspect, top = size / aspect; // Unused values in perspective formula. m[1] = m[2] = m[3] = m[4] = 0; m[6] = m[7] = m[12] = m[13] = m[15] = 0; // Perspective formula. m[0] = 2 * near / (right - left); m[5] = 2 * near / (top - bottom); m[8] = (right + left) / (right - left); m[9] = (top + bottom) / (top - bottom); m[10] = -(far + near) / (far - near); m[11] = -1; m[14] = -(2 * far * near) / (far - near); } And my mView is set using: lookAtMatrix(cameraPos, camLookAt, camUpVector, mView); * UPDATE * I'm going to leave this here in case anyone has a different solution, can explain how they do it, or why this works. This is what I figured out. In my system I use a 10th scale unit to pixels on non-retina displays and a 20th scale on retina displays. The iPhone is 640 pixels wide on retina and 320 pixels wide on non-retina (obsolete). So if I want something to be the full screen width I divide by 20 to get the OpenGL unit width. Then divide that by 2 to get the left and right unit position. Something 32 units wide centered on the screen goes from -16 to +16. Believe it or not I have an excel spreadsheet do all this math for me and output all the vertex data for my sprite sheet. It's an arbitrary thing I made up to do .1 units = 1 non-retina pixel or 2 retina pixels. I could have made it .01 units = 2 pixels and someday I might switch to that. But for now it's the other. So the width of the screen in units is 32.0, and that means the left most pixel is at -16.0 and the right most is at 16.0. After messing a bit I figured out that if I take the [0] value of an identity modelViewProjection matrix and multiply it by 16 I get the depth required to get 1:1 pixels. I don't know why. I don't know if the 16 is related to the screen size or just a lucky guess. But I did a test where I placed a sprite at that calculated depth and varied the FOV through all the valid values and the object stays steady on screen with 1:1 pixels. So now I'm just calculating the unityDepth that way. If someone gives me a better answer I'll checkmark it.

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• Sprite rotation

  - by Kipras

  I'm using OpenGL and people suggest using glRotate for sprite rotation, but I find that strange. My problem with it is that it rotates the whole matrix, which sort of screws up all my collision detection and so on and so forth. Imagine I had a sprite at position (100, 100) and in position (100, 200) is an obstacle and the sprite's facing it. I rotate the sprite away from the obstacle and when move upwards my y axis, even though the projection shows like it's going away from the obstacle, the sprite will intersect it. So I don't see another way of a rotating a sprite and not screwing up all collision detection other than doing mathematical operations on the image itself. Am I right or am I missing something?

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• Vertex data split into separate buffers or one one structure?

  - by kiba2

  Is it better to have all vertex data in one structure like this: class MyVertex { int x,y,z; int u,v; int normalx, normaly, normalz; } Or to have each component (location, normal, texture coordinates) in separate arrays/buffers? To me it always seemed logical to keep the data grouped together in one structure because they'd always be the same for each instance of a shared vertex and that seems to be true for things like character models (ex: the normal should be an average of adjacent normals for smooth lighting). One instance where this doesn't seem to work is other kinds of meshes like say a cube where the texture coordinates for each may be the same but that causes them to be different where the vertices are shared. Does everybody normally keep them separate? Won't this make them less space efficient if there needs to be an instance of texture coordinates and normals for each triangle vertex (They won't be indexed)? Can OpenGL even handle this mixing of indexed (for location) vs non-indexed buffers in the same VBO?

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• Do unused vertices in a 3D object affect performance?

  - by Gajet

  For my game I need to generate a mesh dynamically. Now I'm wondering does it have a noticeable affect in FPS if I allocate more vertices than what I'm actually using or not? and does it matter if I'm using DirectX or OpenGL? Edit Final output will be a w*h cell grid, but for technical issues it's much easier for me to allocate (w+1)*(h+1) vertices. Sure I'll only use w*h vertices in indexing, and I know there is some memory wasting there, but I want to know if it also affect FPS or not? (Note that mesh is only generated once in each time you play the game)

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• How many threads should an Android game use?

  - by kvance

  At minimum, an OpenGL Android game has a UI thread and a Renderer thread created by GLSurfaceView. Renderer.onDrawFrame() should be doing a minimum of work to get the higest FPS. The physics, AI, etc. don't need to run every frame, so we can put those in another thread. Now we have: Renderer thread - Update animations and draw polys Game thread - Logic & periodic physics, AI, etc. updates UI thread - Android UI interaction only Since you don't ever want to block the UI thread, I run one more thread for the game logic. Maybe that's not necessary though? Is there ever a reason to run game logic in the renderer thread?

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• forward rendering and multiple shadow maps

  - by Irbis

  I have two light sources on my scene. I created two fbo's which store depth textures for these lights. A render loop looks like this: bind fbo1 save depth values for first light unbind fbo1 bind fbo2 save depth values for second light unbind fbo2 enable additive blending bind first depth texture render scene bind second depth texture render scene disable additive blending For one light source the program works fine. For many light sources I use an additive blending to acumulate lighting results but then some objects become transparent (for example when an object which is further away from the camera is drawn before an object which is closer to the camera). How to resolve that problem ? How should I accumulate lighting effects for many light sources (many shadow maps) ? P.S. I use OpenGL/GLSL 3.3+

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• How do you load in a .bmp file to use it as a height map in C++?

  - by user1324894

  I need to create a terrain that can be used in C++ and opengl and I am told that using a height map is the way to go. I have a .bmp file that is a greyscale image that I would like to use. However, I do not know how to load that greyscale image into the project so that it can be used as a height map or how I can apply a texture to it to create terrain nor how to compute the normals that I'm told will be required. How would I go about achieving what I would like to do?

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• does unused vertices in a 3D object affect performance?

  - by Gajet

  For my game I need to generate a mesh dynamically. now I'm wondering does it have a noticeable affect in fps if I allocate more vertices than what I'm actually using or not? and does it matter if I'm using DirectX or OpenGL? edit final output will be a w*h cell grid, but for technical issues it's much more easier for me to allocate (w+1)*(h+1) vertices. sure I'll only use w*h vertices in indexing, and I know there is some memory wasting there, but I want to know if it also affect fps or not? (note that mesh is only generated once in each time you play the game)

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• OpenGLES 2.0 gluunProject

  - by secheung

  I've spent more time than i should trying to get my ray picking program working. I'm pretty convinced my math is solid with respect to line plane intersection, but I believe the problem lies with the changing of the mouse screen touch into 3D world space. Heres my code public void passTouchEvents(MotionEvent e){ int[] viewport = {0,0,viewportWidth,viewportHeight}; float x = e.getX(), y = viewportHeight - e.getY(); float[] pos1 = new float[4]; float[] pos2 = new float[4]; GLU.gluUnProject( x, y, 0.0f, mViewMatrix, 0, mProjectionMatrix, 0, viewport, 0, pos1, 0); GLU.gluUnProject( x, y, 1.0f, mViewMatrix, 0, mProjectionMatrix, 0, viewport, 0, pos2, 0); } Just as a reference I've tried transforming the coordinates 0,0,0 and got an offset. It would be appreciated if you would answer using opengl es 2.0 code. Thanks

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• What Shading/Rendering techniques are being used in this image?

  - by Rhakiras

  My previous question wasn't clear enough. From a rendering point of view what kind of techniques are used in this image as I would like to apply a similar style (I'm using OpenGL if that matters): http://alexcpeterson.com/ My specific questions are: How is that sun glare made? How does the planet look "cartoon" like? How does the space around the planet look warped/misted? How does the water look that good? I'm a beginner so any information/keywords on each question would be helpful so I can go off and learn more. Thanks

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• is this the correct way to use glTexCoordPointer?

  - by RubyKing

  Hey all Just trying to work out how to use this function glTexCoordPointer. Here is the man pages http://www.opengl.org/sdk/docs/man/xhtml/glTexCoordPointer.xml which states that I must set a pointer to the first element of the array that uses the texture cordinate. Here is my array static const GLfloat GUIVertices[] = { //FIRST QUAD 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, -1.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, -1.0f, 0.94f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.94f, 0.0f, 1.0f, 1.0f, 1.0f, //2ND QUAD // x y z w X Y 1.0f, -1.0f, 0.0f, 1.0f, 1.0f, 0.0f, -1.0f,-1.0f, 0.0f, 1.0f, 0.0f, 0.0f, -1.0f,-0.94f, 0.0f,1.0f, 0.0f, 1.0f, 1.0f, -0.94f, 0.0f,1.0f, 1.0f, 1.0, }; But how do I set the pointer correctly? like this glTexCoordPointer(1, GL_FLOAT, 6, reinterpret_cast(29 * sizeof(float)) ); for the fifth element on the 2nd quad first row. any help is thankful

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• Why does DirectX use a left-handed coordinate system?

  - by greyfade

  I considered posting on Stack Overflow, but the question strikes me as being far too subjective since I can't think of a reasonable technical explanation for Microsoft's choice in this matter. But this question has bugged me for so long and the issue keeps coming up in one of my projects, and I have never actually seen an attempt at explaining this: OpenGL uses a right-handed coordinate system, where the +Z part of the world coordinate system extends toward the viewer. DirectX uses a left-handed system where the +Z part of the world coordinate extends into the screen, away from the viewer. I never used the Glide API, so I don't know how it worked, but from what I can gather, it uses a left-handed system as well. Is there a technical reason for this? And if not, is there some conceptual advantage to a particular handedness of a coordinate system? Why would one choose one over the other?

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• How to render a texture partly transparent?

  - by megamoustache

  Good Morning StackOverflow, I'm having a bit of a problem right now as I can't seem to find a way to render part of a texture transparently with openGL. Here is my setting : I have a quad, representing a wall, covered with this texture (converted to PNG for uploading purposes). Obviously, I want the wall to be opaque, except for the panes of glass. There is another plane behind the wall which is supposed to show a landscape. I want to see the landscape from behind the window. Each texture is a TGA with alpha channel. The "landscape" is rendered first, then the wall. I thought it would be sufficient to achieve this effect but apparently it's not the case. The part of the window supposed to be transparent is black and the landscape only appears when I move past the wall. I tried to fiddle with GLBlendFunc() after having enabled it but it doesn't seem to do the trick. Am i forgetting an important step ? Thank you :)

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• Rotate an object given only by its points?

  - by d33tah

  I was recently writing a simple 3D maze FPP game. Once I was done fiddling with planes in OpenGL, I wanted to add support for importing Blender objects. The approach I used was triangulization of the object, then using Three.js to export the points to plaintext and then parsing the result JSON in my app. The example file can be seen here: https://github.com/d33tah/tinyfpp/blob/master/Data/Models/cross.txt The numbers represent x,y,z,u,v of a single vertex, which combined in three make a triangle. Then I rendered such an object triangle-by-triangle and played with it. I could move it back and forth and sideways, but I still have no idea how to rotate it by some axis. Let's say I'd like to rotate all the points by five degrees to the left, how would a code doing it look like?

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• 2D Game Development dynamics in c++ [on hold]

  - by novice

  I am new to developing computer graphic applications in c++ using OpenGl. I want to develop games but I really am facing problems when it comes to understanding concepts like trajectory, collisions, gravity and also the use of various physics engines that are available. when i search the internet I kind of get lost because they aren't for beginners like me. There is some hardcore mathematics, physics and coding involved. I need to pick the concepts that are mostly needed in game dev like trajectory, collision etc. Any good tutorials that can help me out in picking these concepts from the start.

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• 3D primitive rendering library

  - by tomzx

  Hi, I am looking for a library which would easily allow me to render shapes (cubes, spheres, lines, circles, etc.) in 3D3 and OpenGL if possible. I want to be able to rapidly design visual debugging tools and I am not proefficient enough in graphics rendering to do it myself (writing the low level stuff that is). The library would have to be for C/C++. I've already taken a look at the open-source 3d engine, but I feel those are too big for what I really need. Do any of you know if such library exist? If so, links would be appreciated!

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