[Public WebGL] createTextures vs. genTexture 2^32 limit

Glenn Maynard [email protected]
Sun Apr 15 08:18:59 PDT 2012


In OpenGL ES, genTexture appears to be underdefined after the first 2^32
calls:

> void GenTextures( sizei n, uint *textures ); returns n previously unused
texture object names in textures. These names are marked as used, for the
purposes of GenTextures only, ...

That is, even after a glDeleteTextures() call on a texture, glGenTextures
will never return the same value again.  However, the ES spec doesn't
appear to say what happens if it runs out--if you overflow uint.

It's definitely possible to call createTexture() 2^32 times; in Chrome 18
on my system, it takes about three hours.  This shouldn't happen in
well-written programs, but it still needs to be defined.

I'm not actually concerned about ES's behavior here, since WebGL's texture
objects don't expose integer texture IDs.  However, the underdefined
overflow problem is inherited by WebGL, since createTexture is defined in
terms of genTextures.

WebGL can avoid this by not defining createTexture() in terms of
glGenTextures.  Instead, say: "Create a WebGLTexture object and initialize
it with a texture object name not in use by any other WebGLTexture in this
context."  That's still valid, since OpenGL doesn't actually require that
you use glGenTextures.

The same applies to the other create* functions as well, of course.

(I'd call this one low-priority, but a good thing to tighten up.)

-- 
Glenn Maynard
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