Tagged Questions

1
vote
2answers
74 views

Calling glGetError() in release builds?

Currently, I'm calling glGetError() after each OpenGL function call in order to be able to detect and report bugs. I've been reading that glGetError() calls should be reduced to once per frame in ...
2
votes
1answer
89 views

Proper way to maintain Vertex Buffer Objects

I've started learning WebGL, currently I'm building a 2D lighting system, but there is some confusion going on inside my head. How the lighting works is based on this tutorial ...
3
votes
1answer
111 views

Cut a translucent square in a texture

How to remove (cut-out) a transparent rectangle in a Texture, so that the hole will be translucent. On Android I would use the Xfermodes approach: ...
1
vote
2answers
93 views

How to get a texture from current point of view in OpenGL 2.0 ES?

Probably the title is confusing, but I didn't know how to ask better, sorry about that. What I would like to do is get a bitmap texture that represents exactly what's rendered at one point in time and ...
0
votes
3answers
194 views

Why doesn't glBindVertexArray work in this case?

From my understanding of what glBindVertexArray does and how it works, the following code should work fine: First init: glGenVertexArraysOES(1, &_vertexArray); ...
3
votes
1answer
141 views

Fill texture with white color

How to paint texture with white color? Example what I mean: SpriteBatch.setColor changes tint only.
0
votes
1answer
86 views

OpenGL RTT FrameBuffer question and Rendering to texture while sampling it

What i need to do: Blur the selected texture and pass the texture to another effect for postprocessing. Notice that i want one texture passed all over. How do i want to do this: Bind the FBO ( ...
12
votes
2answers
326 views

OpenGL: Where shoud I place shaders?

I'm trying to learn OpenGL ES 2.0 and I'm wondering what is the most common practice to "manage" shaders. I'm asking this question because in the examples I've found (like the one included in the API ...
2
votes
0answers
349 views

exporting bind and keyframe bone poses from blender to use in OpenGL

EDIT: I decided to reformulate the question in much simpler terms to see if someone can give me a hand with this. Basically, I'm exporting meshes, skeletons and actions from blender into an engine ...
2
votes
1answer
176 views

Is there any reason not to save skinning animation data in texture?

I have thought about saving animation data in texture. I think I can save shader parameter setting and interpolation cost in CPU, and also enable animated instancing. But I couldn't find no text ...
1
vote
3answers
254 views

OpenGL are strips/fans faster for rendering or just data bandwidth

When we send data for drawing we can mark it as TRIANGLE_STRIP or TRIANGLE_FAN to reduce the number of vertices we have to specify. Now, does this actually improve the rendering speed on the graphics ...
4
votes
1answer
490 views

Multiplication for MVP matrices: Any benefits to doing so within the vertex shader?

I'd like to understand under what circumstances (if any) it is worth doing MVP matrix multiplication inside a vertex shader. The vertex shader is run once per vertex, and a single mesh typically ...
6
votes
4answers
440 views

Impact of variable-length loops on GPU shaders

Its popular to render procedural content inside the GPU e.g. in the demoscene (drawing a single quad to fill the screen and letting the GPU compute the pixels). Ray marching is popular: This means ...
3
votes
4answers
2k views

Geometry instancing in OpenGL ES 2.0

I am planning to do geometry instancing in OpenGL ES 2.0 Basically I plan to render the same geometry(a chair) maybe 1000 times in my scene. What is the best way to do this in OpenGL ES 2.0? I am ...
0
votes
1answer
268 views

Straightforward guidelines for converting OpenGL to OpenGL ES?

Is there a straightforward list of finite steps that I need to follow to convert an OpenGL program into an OpenGL ES that's used on the iPhone and iPad? I'd be using GLKit. I've seen some similar API ...
6
votes
1answer
611 views

How can I organize render and transformation data in a scalable fashion?

I am writing for OpenGL 2.0 and in the future porting to OpenGL ES 2.0. I only use VBOs and shaders (no immediate mode, no vertex arrays). I already have working solutions, they just... feel wrong. ...
8
votes
3answers
2k views

How can I bend an object in OpenGL?

Is there a way one could bend an object, like a cylinder or a plane using OpenGL? I'm an OpenGL beginner (I'm using OpenGL ES 2.0, if that matters, although I suspect, math matters most in this case, ...
3
votes
1answer
803 views

How can I create an orthographic display that handles different screen dimensions?

I'm trying to create an iPad/iPhone game using GLES2.0 that contains a 3D scene with a heads-up-display/GUI overlaid on the top. However, this problem would also apply if I were to port my game to a ...
5
votes
2answers
731 views

Getting the number of fragments which passed the depth test

In "modern" environments, the "NV Occlusion Query" extension provides a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension ...
1
vote
1answer
1k views

How can I write only to the stencil buffer in OpenGL ES 2.0?

I'd like to write to the stencil buffer without incurring the cost of my expensive shaders. As I understand it, I write to the stencil buffer as a 'side effect' of rendering something. In this first ...
3
votes
1answer
1k views

How should I move 2D objects in OpenGL ES 2?

I am a bit confused about what I need to move a basic square. Should I use a translation matrix or just change the object vertices? Which one is better? I use a simple vertex shader, gl_Position = ...