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captainfreedom

OpenGL glTexImage2D with GL_ALPHA

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I am using opengl es. I thought that I would be saving memory by using glTexImage2D with GL_ALPHA rather than GL_RGBA, but according to the documentation (http://www.khronos.org/opengles/documentation/opengles1_1/gl_egl_ref_1_1_20041110/glTexImage2D.html) everything is just converted to RGBA in the end, so it makes no difference. Is this right?

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The function behaves as if it was expanded to RGBA with fixed RGB values, but that doesn't mean it actually happens. That is an implementation detail you don't know about.

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There are internal 8bpp formats, GL_LUMINANCE8 is usually preferred, I think. In your shader, all 4 components of texel.xyzw are filled with the same value.

Also, there are many alias-names to the same really-internal format, which is making things confusing imho. I rely on vendor-provided (nVidia/AMD) examples for how to define texture-formats.

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