blob: c233773e5f5f773365a5b3cb95edb2bd3d82db4e [file] [log] [blame]
Name
SGIX_fog_blend_alpha
SGIX_fog_blend_color
Name Strings
GL_SGIX_fog_blend
Version
$Date: 1997/09/15 19:26:36 $ $Revision: 1.3 $
Number
????
Dependencies
XXX
Overview
This extension affect the way the fog coefficient (f) is used to
blend the rasterized fragments in non-indexed color mode.
When enabled using the GL_FOG_BLEND_ALPHA_SGIX parameter,
the alpha component of the fog color is used to change the
resulting alpha, as well as the RGB components.
The color components may stay unchanged by the fog computation
if the GL_FOG_BLEND_COLOR_SGIX is disabled.
No change is done to the equation C = f*Cr + (1-f)Cf
New Procedures and Functions
None
New Tokens
Accepted by the <cap> parameter of Enable, Disable, and IsEnabled
GL_FOG_BLEND_ALPHA_SGIX 0x81FE
GL_FOG_BLEND_COLOR_SGIX 0x81FF
Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
None
Additions to Chapter 3 of the 1.0 Specification (Rasterization)
3.9 Fog
... (The rasterized fragment's A value is not changed by fog blending.)...
is removed and replaced by.
The rasterized fragment alpha value is not changed by the fog blending,
unless specified otherwise by enabling it with the GL_FOG_BLEND_ALPHA_SGIX
parameter. Color modifications can be turned off by disabling with
the GL_FOG_BLEND_COLOR_SGIX paramater.
Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations
and the Framebuffer)
None
Additions to Chapter 5 of the 1.0 Specification (Special Functions)
None
Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
Fog alpha blend enable/disable state is checked by calling glIsEnable
function with GL_FOG_BLEND_ALPHA_SGIX parameter.
Fog color blend enable/disable state is checked by calling glIsEnable
function with GL_FOG_BLEND_COLOR_SGIX parameter.
When PushAttrib is called with FOG_BIT enabled, the state of the
fog color and alpha blend is pushed. When an attribute set
that includes enable information is popped, the state of the fog
color and alpha blend is restored to the pushed value.
Additions to the GLX Specification
None
Errors
None
New State
Get Value Get Command Type Initial Value Attribute
--------- ----------- ---- ------------- ---------
FOG_BLEND_ALPHA_SGIX IsEnabled B FALSE fog
FOG_BLEND_COLOR_SGIX IsEnabled B TRUE fog
New Implementation Dependent State
None