WebGL parameter - "must be zero" - why provide it?

3
votes

framebufferTexture2D has several arguments of which last one is level.

A GLint specifying the mipmap level of the texture image to be attached. Must be 0.

If it must be zero, why do we have to specify it?

1
webgl
Seems it was "copy-pasted" from the OpenGL ES 2 spec: khronos.org/registry/OpenGL-Refpages/es2.0/xhtml/… - UnholySheep

1 Answers

3
votes

It's based on the OpenGL ES 2 spec, and doing it this way enables better forwards compatibility. There's no logical reason why the mipmap level has to be zero (aside from the fact the spec currently doesn't support it), so it enables future versions of the spec the ability to widen the scope of that argument and allow other values without changing the method signature.

This has indeed already happened in OpenGL ES 3, which no longer requires the parameter to be zero in all cases.