OpenGL.GL.ARB.texture_query_levels

OpenGL extension ARB.texture_query_levels

This module customises the behaviour of the OpenGL.raw.GL.ARB.texture_query_levels to provide a more Python-friendly API

Overview (from the spec)

This extension provides a new set of texture functions (textureQueryLevels) in the OpenGL Shading Language that exposes the number of accessible mipmap levels in the texture associated with a GLSL sampler variable. The set of accessible levels includes all the levels of the texture defined either through TexImage*, TexStorage*, or TextureView* (ARB_texture_view) APIs that are not below the TEXTURE_BASE_LEVEL or above the TEXTURE_MAX_LEVEL parameters. For textures defined with TexImage*, the set of resident levels is somewhat implementation-dependent. For fully defined results, applications should use TexStorage*/TextureView unless the texture has a full mipmap chain and is used with a mipmapped minification filter.

These functions means that shaders are not required to manually recompute, approximate, or maintain a uniform holding a pre-computed level count, since the true level count is already available to the implementation. This value can be used to avoid black or leaking pixel artifacts for rendering methods which are using texture images as memory pages (eg: virtual textures); methods that can't only rely on the fixed pipeline texture functions which take advantage of TEXTURE_MAX_LEVEL for their sampling.

The official definition of this extension is available here: http://www.opengl.org/registry/specs/ARB/texture_query_levels.txt