[OpenGL] Best approach to setting every pixel's color

[Antony Kossoski]

I'm working on a 2D surface, where n kinds of lighting spheres move along with my mouse. Every pixel's color got to be calculated per movement, since it is obtained by the distance between the pixel and all of the sphere's centers. This way, I have n * width * height calculations per frame, and that's a lot of work when trying to reach 60 fps with a 1024x768 resolution and with n = 3 or so.

I want to know the fastest (doesn't mean the easiest) way to do such thing in OpenGL.

Thanks

[manasij7479]

I want to know the fastest (doesn't mean the easiest) way to do such thing in OpenGL.

Write a fragment shader in glsl.

[VirtualAce]

Any time you need to touch texels or pixels you should do so in a shader regardless if you using Direct3D or OpenGL. Doing this in any other place is going to impact performance. Note that although shaders are blazing fast you can slow them down by adding texel fetches when they are not needed.

[Antony Kossoski]

Thank you both for the answers.

Because I want the pixels to be update per mouse movement, shoud I declare 2 uniform variables (x, y) in my fragment shader and update them every frame with glUniform...?