Passing int array to fragment shader

Question

I'm attempting to plot an iterative function in OpenGL ES. An array of ints is being updated with how often a given pixel is hit by the iterative function. I'd like to pass this density array to a fragment shader and use it to plot the result on a simple quad covering the whole screen.

My question is: can I pass this array directly to the shader as a uniform and generate pixels by using gl_FragCoord to look up the density for the given position

or

should I rather use the array to create a texture with one channel using GL_LUMINANCE and pass that to the shader?

Dr. Snoopy · Accepted Answer · 2010-12-02 12:41:25Z

4

You have a limited number of uniforms available, and the indexing might be troubling since not all GPUs support non-constant indexing. A 2D Nx1 texture doesn't have any of these issues but will return values into the [0, 1] range. You can scale back this values to obtain the original integer and use it.

answered Dec 2, 2010 at 12:41

Dr. Snoopy

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2 Comments

Kos Over a year ago

Why not use a 1D texture instead of 2D 1xN texture? BTW- Could you specify which GPUs don't support non-constant indexing? Would sure be useful to know :)

Dr. Snoopy Over a year ago

@Kos: Because OpenGL ES 2.0 doesn't support 1D textures.

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