XXX - Not complete yet!!! But pretty close.
Name
SGIX_blend_alpha_minmax
Name Strings
GL_SGIX_blend_alpha_minmax
Version
$Date: 1998/03/31 00:55:21 $ $Revision: 1.3 $
Number
119
Dependencies
EXT_blend_minmax is required
EXT_blend_subtract affects the number of values of BLEND_EQUATION_EXT
Overview
Two additional blending equations are specified using the interface
defined by EXT_blend_minmax. These equations are similar to the
MIN_EXT and MAX_EXT blending equations, but the outcome for all four
color components is determined by a comparison of just the alpha
component's source and destination values. These equations are useful
in image processing and advanced shading algorithms.
New Procedures and Functions
None
New Tokens
Accepted by the parameter of BlendEquationEXT:
ALPHA_MIN_SGIX 0x8320
ALPHA_MAX_SGIX 0x8321
Additions to Chapter 2 of the GL Specification (OpenGL Operation)
None
Additions to Chapter 3 of the GL Specification (Rasterization)
None
Additions to Chapter 4 of the GL Specification (Per-Fragment Operations
and the Framebuffer)
Two additional blending equations are defined. If BlendEquationEXT is
called with set to ALPHA_MIN_EXT, the blending equation becomes
/ Cs As < Ad
C' = (
\ Cd As >= Ad
where C' is the color resulting from the blending operation,
Cs and Cd are the source and destination colors, and As and Ad
are the source and destination alpha in particular.
If BlendEquationEXT is called with set to ALPHA_MAX_SGIX, the
blending equation becomes
/ Cs As > Ad
C' = (
\ Cd As <= Ad
In both cases the blending equation is evaluated separately for each
color component in a quadruplet.
Additions to Chapter 5 of the GL Specification (Special Functions)
None
Additions to Chapter 6 of the GL Specification (State and State Requests)
None
Additions to the GLX Specification
None
GLX Protocol
None
Dependencies on EXT_blend_minmax
EXT_blend_minmax is required.
Errors
INVALID_ENUM is generated by BlendEquationEXT if its single parameter
is not FUNC_ADD_EXT, MIN_EXT, MAX_EXT, FUNC_SUBTRACT_EXT,
FUNC_REVERSE_SUBTRACT_EXT, ALPHA_MIN_SGIX, or ALPHA_MAX_SGIX.
INVALID_OPERATION is generated if BlendEquationEXT is executed between
the execution of Begin and the corresponding execution to End.
New State
Two new values of BLEND_EQUATION_EXT:
Get Value Get Command Type Initial Value Attribute
--------- ----------- ---- ------------- ---------
BLEND_EQUATION_EXT GetIntegerv Z7 FUNC_ADD_EXT color-buffer
New Implementation Dependent State
None