EXT_shader_integer_mix

Name

EXT_shader_integer_mix

Name Strings

GL_EXT_shader_integer_mix

Contact

Matt Turner (matt.turner 'at' intel.com)

Contributors

Matt Turner, Intel
Ian Romanick, Intel
  

Status

Shipping

Version

Last Modified Date:         09/12/2013
Author Revision:            6
  

Number

OpenGL Extension #437
OpenGL ES Extension #161 
  

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_EXT_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_EXT_shader_integer_mix        1

Interactions with ARB_ES3_compatibility

On desktop implementations that support ARB_ES3_compatibility,
GL_EXT_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
----  --------    --------  ---------------------------------------------
  6   09/12/2013  idr       After discussions in Khronos, change vendor
                            prefix to EXT.

  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
  