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Name
MESA_shader_integer_mix
Name Strings
GL_MESA_shader_integer_mix
Contact
Matt Turner (matt.turner 'at' intel.com)
Contributors
Matt Turner, Intel
Ian Romanick, Intel
Status
Shipping
Version
Last Modified Date: 09/09/2013
Author Revision: 5
Number
Dependencies
OpenGL 3.0 or OpenGL ES 3.0 is required. This extension interacts with
GL_ARB_ES3_compatibility.
This extension is written against the OpenGL 4.4 (core) specification
and the GLSL 4.40 specification.
Overview
GLSL 1.30 (and GLSL ES 3.00) expanded the mix() built-in function to
operate on a boolean third argument that does not interpolate but
selects. This extension extends mix() to select between int, uint,
and bool components.
New Procedures and Functions
None.
New Tokens
None.
Additions to Chapter 8 of the GLSL 4.40 Specification (Built-in Functions)
Modify Section 8.3, Common Functions
Additions to the table listing common built-in functions:
Syntax Description
--------------------------- --------------------------------------------------
genIType mix(genIType x, Selects which vector each returned component comes
genIType y, from. For a component of a that is false, the
genBType a) corresponding component of x is returned. For a
genUType mix(genUType x, component of a that is true, the corresponding
genUType y, component of y is returned.
genBType a)
genBType mix(genBType x,
genBType y,
genBType a)
Additions to the AGL/GLX/WGL Specifications
None.
Modifications to The OpenGL Shading Language Specification, Version 4.40
Including the following line in a shader can be used to control the
language features described in this extension:
#extension GL_MESA_shader_integer_mix : <behavior>
where <behavior> is as specified in section 3.3.
New preprocessor #defines are added to the OpenGL Shading Language:
#define GL_MESA_shader_integer_mix 1
Interactions with ARB_ES3_compatibility
On desktop implementations that support ARB_ES3_compatibility,
GL_MESA_shader_integer_mix can be enabled (and the new functions
used) in shaders declared with '#version 300 es'.
GLX Protocol
None.
Errors
None.
New State
None.
New Implementation Dependent State
None.
Issues
1) Should we allow linear interpolation of integers via a non-boolean
third component?
RESOLVED: No.
2) Should we allow mix() to select between boolean components?
RESOLVED: Yes. Implementing the same functionality using casts would be
possible but ugly.
Revision History
Rev. Date Author Changes
---- -------- -------- ---------------------------------------------
5 09/09/2013 idr Add ARB_ES3_compatibility interaction.
4 09/06/2013 mattst88 Allow extension on OpenGL ES 3.0.
3 08/28/2013 mattst88 Add #extension/#define changes.
2 08/26/2013 mattst88 Change vendor prefix to MESA. Add mix() that
selects between boolean components.
1 08/26/2013 mattst88 Initial revision
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