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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,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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    Depth test

Tests:
 + dEQP-GLES2.functional.depth.*

Includes:
 + Depth buffer update when rendering triangles with GL_ALWAYS
 + Depth test when rendering triangles
 + All depth comparison functions

Excludes:
 + Lines and points
 + Depth mask
 + glPolygonOffset()
 + Overlapping primitives in single draw call
 + Interaction with stencil test

Description:

Each test case renders 4 pairs of quads, arranged in a 2x2 grid. First
quad is rendered with GL_ALWAYS depth test mode, while the second uses
the depth test mode stated in test case name. First pair of quads have
exactly same z, in the second pair z1 < z2 and in the third pair z2 < z1.
In the fourth pair z1 = 0 and z2 is interpolated between -1.0 and 1.0,
e.g. the quads are intersecting.

The first quad in each pair is red, while the second one is green.
The resulting image depends on the depth test mode used when rendering
the second quads.

Test results are verified by comparing the rendered image against a
reference image. The reference is rendered using a simplified model
of the GL rendering pipe.