OpenGL is a graphics standard and API which targets the desktop and workstation markets. It is designed to be easy to accelerate with dedicated computer hardware, and hence most implementations give greatly improved performance over traditional software rendering. Currently, OpenGL is used for ...

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OpenGL Performance Questions

This subject, as with any optimisation problem, gets hit on a lot, but I just couldn't find what I (think) I want. A lot of tutorials, and even SO questions have similar tips; generally covering: ...
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3answers
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Order independent transparency in particle system

I'm writing a particle system and would like to find a trick to achieve proper alpha blending without sorting particles because: Each particle is a point sprite in a single mesh and I can't use ...
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1answer
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Texture mapping on gluDisk

I'm trying to map a brick texture on the edge of a fountain and I'm using gluDisk for that. How can I make the right coordinates for the disk? My code looks like this and I have only found a function ...
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6answers
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Correct level of abstraction for a 3d rendering component?

I've seen lots of questions around this area but not this exact question so apologies if this is a duplicate. I'm making a small 3d game. Well to be honest, it's just a little hobby project and ...
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2answers
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How to deal with OpenGL and Fullscreen on OS X

I do most of my development on OS X and for my current game project this is my target environment. However when I play games I play on Windows. As a windows gamer I am used to Alt+Tab switching from ...
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How do I draw a point sprite using OpenGL ES on Android?

Edit: I'm using the GL enum, which is incorrect since it's not part of OpenGL ES (see my answer). I should have used GL10, GL11 or GL20 instead. Here's a few snippets of what I have so far... void ...
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2answers
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Double sides face with two normals

I think this isn't possible, but I just want to check this: Is it possible to create a face in opengl that has two normals? So: I want the inside and outside of some cilinder to be drawn, but I ...
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4answers
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2D Platformer Collision Handling

I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font ...
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4answers
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How to improve batching performance

I am developing a sprite based 2D game for mobile platform(s) and I'm using OpenGL (well, actually Irrlicht) to render graphics. First I implemented sprite rendering in a simple way: every game object ...
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2answers
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OpenGL - Stack overflow if I do, Stack underflow if I don't!

I'm in a multimedia class in college, and we're "learning" OpenGL as part of the class. I'm trying to figure out how the OpenGL camera vs. modelview works, and so I found this example. I'm trying to ...
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7answers
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Library to load images into textures, Linux, C and OpenGl

I am looking for simple, self-contained C library for Linux to load images from files into OpenGL textures. The licence should be quite liberal: zlib, bsd, mit or something. I have found SOIL, however ...
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3D primitive rendering library

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 ...
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OpenGL ES 2.0: Vertex and Fragment Shader for 2D with Transparency

Could I knindly ask for correct examples of OpenGL ES 2.0 Vertex and Fragment shader for displaying 2D textured sprites with transparency? I have fairly simple shaders that display textured polygon ...
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2answers
318 views

Manually invoke key callback in (free)glut

I have to watch the keyboard during rendering. So, is there a way to force glut to invoke the Keyboard callback immediately?
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1answer
213 views

Can I change the order of these OpenGL / Win32 calls?

I've been adapting the NeHe OpenGL/Win32 code to be more object-oriented and I don't like the way some of the calls are structured. The example has the following pseudo-structure: Register ...
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2answers
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How can I convert a mouse click to a ray?

I have a perspective projection. When the user clicks on the screen, I want to compute the ray between the near and far planes that projects from the mouse point, so I can do some ray intersection ...
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1answer
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Restoring projection matrix

I am learning to use FBOs and one of the things that I need to do when rendering something onto user defined FBO, I have to setup the projection, modelview and viewport for it. Once I am done ...
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3answers
1k views

Multiple Vertex Buffers per Mesh

I've run into the situation where the size of my mesh with all its vertices and indices, is larger than the (optimal) vertex buffer object upper limit (~8MB). I was wondering if I can sub-divide the ...
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2answers
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View matrix in opengl

Sorry for my clumsy question. But I don't know where I am wrong at creating view matrix. I have the following code: createMatrix(vec4f(xAxis.x, xAxis.y, xAxis.z, dot(xAxis,eye)), vec4f( yAxis.x_,...
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1answer
4k views

Computing a normal matrix in conjunction with gluLookAt

I have a hand-rolled camera class that converts yaw, pitch, and roll angles into a forward, side, and up vector suitable for calling gluLookAt. Using this camera class I can modify the model-view ...
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1answer
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How to use OpenGL blend mode/functions to brighten/darken a texture.

Tried this code, but the texture didnot get any lighter. try { texture = TextureLoader.getTexture("png", Game.class.getResourceAsStream("/brick....
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1answer
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Atmospheric Scattering

I'm trying to implement atmospheric scattering based on Sean O`Neil algorithm that was published in GPU Gems 2. But I have some trouble getting the shader to work. I've downloaded sample code of O`...
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2answers
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FrameBuffer Render to texture not working all the way

I am learning to use Frame Buffer Objects. For this purpose, I chose to render a triangle to a texture and then map that to a quad. When I render the triangle, I clear the color to something blue. So,...
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2answers
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GLSL Shader Effects: How to do motion blur, etc?

I am not sure how right it is to ask this question, but still here it goes. I have a full 2D environment, with sprites going around as landscape, characters, etc And to make it more state-of-art ...
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1answer
767 views

Broken alpha of two-sided OpenGL mesh

How do I get rid of this alpha transparency artifacting with classic fixed function OpenGL? I tried all kinds of settings but I'm not sure why it's good in the upper half of the mask but not in the ...
5
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3answers
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how to add water effect to an image

This is what I am trying to achieve: A given image would occupy say 3/4th height of the screen. The remaining 1/4th area would be a reflection of it with some waves (water effect) on it. I'm not sure ...
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2answers
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OpenGL ES 2.0: Picking Individual Polygon Sprites from within VBO

Say, I send 10 polygon pairs (one polygon pair == one 2d sprite == one rectangle == two triangles) into OpenGL ES 2.0 VBO. The 10 polygon pairs represent one animated 2D object consisting of 10 frames....
17
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1answer
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GLSL: How do I cast a float to an int?

In a GLSL fragment shader I am trying to cast a float into an int. The compiler raises an error: ERROR: 0:60: '=' : cannot convert from 'mediump float' to 'highp int' I tried raising the precision ...
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1answer
412 views

Mandelbrot set not displaying properly

I am trying to render mandelbrot set using glsl. I'm not sure why its not rendering the correct shape. Does the mandelbrot calculation require values to be within a range for the (x,y) [ or (real, ...
6
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2answers
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OpenGL ES 2.0: Using VBOs?

OpenGL VBOs (vertex buffer objects) have been developed to improve performance of OpenGL (OpenGL ES 2.0 in my case). The logic is that with the help of VBOs, the data does not need to be copied from ...
7
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4answers
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glsl demo suggestions?

In a lot of places I interviewed recently, I have been asked many a times if I have worked with shaders. Even though, I have read and understand the pipeline, the answer to that question has been no. ...
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4answers
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Setting up OpenGL camera with off-center perspective

I'm using OpenGL ES (in iOS) and am struggling with setting up a viewport with an off-center distance point. Consider a game where you have a character in the left hand side of the screen, and some ...
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2answers
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A good way to build a game loop in OpenGL

I'm currently beginning to learn OpenGL at school, and I've started making a simple game the other day (on my own, not for school). I'm using freeglut, and am building it in C, so for my game loop I ...
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2answers
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How do I change a sprite's color?

In my rhythm game, I have a note object which can be of a different color depending on the note chart. I could use a sprite sheet with all the different color variations I use, but I would prefer to ...
2
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2answers
658 views

Make OpenGL game perform better

I have programmed an OpenGL game which just contains one F1 car and a track. It is very simple and only uses around of 10'000 - 20'000 triangles. It should run on any PC but it won't, it needs a ...
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3answers
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Missing features from WebGL and OpenGL ES

I've started using WebGL and am pleased with how easy it is to leverage my OpenGL (and by extension OpenGL ES) experience. However, my understanding is as follows: OpenGL ES is a subset of OpenGL ...
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1answer
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Using gluLookAt to move camera in 2D iPhone game?

I'm trying to use gluLookAt to move the camera in my iPhone game, but every time I've tried to use gluLookAt my screen just goes "blank" ( grey in this case ) I'm trying to render a simple triangle ...
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2answers
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In OpenGL, how can I discover the depth range of a depth buffer?

I am doing a GL multi-pass rendering app for iOS. The first pass renders to a depth buffer texture. The second pass uses the values in the depth buffer to control the application of a fragment shader. ...
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4answers
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Vertex Array Object (OpenGL)

I've just started out with OpenGL I still haven't really understood what Vertex Array Objects are and how they can be employed. If Vertex Buffer Object are used to store vertex data (such as their ...
32
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5answers
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Should I use textures not sized to a power of 2?

In the early days of OpenGL and DirectX, texture sizes were required to be powers of two. This meant interpolation of float values could be done very quickly, using shifting and such. Since OpenGL 2....
10
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2answers
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Efficient skeletal animation

I am looking at adopting a skeletal animation format (as prompted here) for an RTS game. The individual representation of each model on-screen will be small but there will be lots of them! In ...
3
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2answers
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Implementing camera for 2d side scroller game?

I'm implementing a 2D side scroller for iOS (using C/C++ with OpenGL) (beat'em up style like double dragon/final fight ). My scenes are composed of one cyclical background image ( the end of the ...
8
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1answer
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Sprite sheets with buffer objects and shaders

What is the "best" way to handle sprite sheets with shaders and buffers? In immediate mode it is easy to modify a sprite's texcoords when it is drawn, but I don't know how to do this with modern ...
3
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2answers
562 views

WinAPI window taking 50% of CPU when idle

I'm currently working on a game that creates a window using WindowsAPI. However, at the moment the process is taking up 50% of my CPU. All I am doing is creating the window and looping using the ...
7
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2answers
670 views

OpenGL or OpenGL ES

What should I learn? OpenGL 4.1 or OpenGL ES 2.0? I will be developing desktop applications using Qt but I may start developing mobile applications in a few months, too. I don't know anything about ...
6
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3answers
2k views

Common light map practices

My scene consists of individual meshes. At the moment each mesh has its associated light map texture, I was able to implement the light mapping using these many small textures. 1) Of course, I want ...
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3answers
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What is the difference between OpenGL 1.x and 2.x?

Is there a good tutorial that shows the difference between OpenGL 1.* and 2.*? It would be very helpful to know which functions I should not be calling (like glBegin(), I assume).
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1answer
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Why does glGetUniformLocation report some of my uniform locations as -1?

I have been writing GLSL shaders for over a year but this is the first time I have run into this problem. I am on the iOS platform - if that matters. In a vertex shader I have this: uniform mediump ...
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2answers
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opengl memory issue - quite strange

I have heard that textures consumes lot of memory but I am surprised how much.... I have 7 textures 1024 16 bit each. And while I will run my app it consumes 57MB of memory. I think that this is "a ...
3
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1answer
995 views

Is there a global “low resolution” filter for OpenGL?

I'm trying to learn a little about OpenGL, so I'm making a simple 2D game (with OpenTK), and so far it's coming along well. I thought it would be fun to give it that, for lack of a better word, ...