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drawElements Quality Program Test Specification
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Copyright 2014 The Android Open Source Project

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
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    Mipmapping tests

Tests:
 + dEQP-GLES3.functional.texture.mipmap.*

Includes:
 + All mipmap filtering modes
 + Lod computation verification
 + Affine and projected transforms
 + User-supplied bias to texture lookup
 + Lod controls: min and max lod
 + 2D and cube map textures

Excludes:
 + Only selected texture formats are exercised

Description:

Mipmapping tests render a pre-defined grid of quads. For 2D textures regular
4x4 grid layout is used. For cube map textures the viewport is recursively
subdivided into smaller areas and each is filled with samples from single
cube face.

Each texture level is filled with single color. However, each mipmap level
gets assigned a different color from a continuous gradient. Thus it is possible
to evaluate how accurately the lod was computed by inspecting the resulting
colorbuffer.

OpenGL ES specification allows approximating both derivate- and lod computation.
Thus two reference images are rendered: one rendered according to the minimum
bound for the approximation and another based on the maximum bound. The rendered
pixels must be in between the two bounds in order to be valid. In order to
compensate the derivate approximation the pixels are actually checked against
a 3x3 neighbor around the pixel.