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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
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    Instanced rendering tests

Tests:
 + dEQP-GLES3.functional.instanced.*

Includes:
 + Draw using:
   - glDrawArraysInstanced()
   - glDrawElementsInstanced()
 + Do instancing using:
   - gl_InstanceID vertex shader input
   - glVertexAttribDivisor()
   - Mixture of the above
 + Instance counts 1, 2, 4, 20
 + Instanced attribute tests with different types

Description:

For each instance a rectangle-shaped grid of triangles is drawn. Instanced
variables are rectangle offset and color components R, G and B. Offsets are
chosen such that the rectangles are drawn next to each other.

In the cases that test draw function, instancing method and instance count, the
instance variables are either calculated based on gl_InstanceID in the vertex
shader or given to the vertex shader as attributes instanced with
glVertexAttribDivisor(). In a mixed case different methods are used for
different variables. Instanced attributes are of type float, except for the
offset attribute, which is of type vec3.

In the tests for instanced attribute types, only the vertex attribute divisor
method is used. The instanced attributes for color components R, G and B are
all int, uint, float or corresponding vectors, or matrices. The instance offset
attribute is of type vec3. In these cases, draw function and instance count are
fixed to glDrawArraysInstanced() and 4, respectively.

In all cases, the resulting image is compared against a reference image
produced by a reference renderer.