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GL_NV_texture_env_combine4
NV_texture_env_combine4
Name Strings
GL_NV_texture_env_combine4
Contact
Michael Gold, NVIDIA Corporation (gold 'at' nvidia.com)
Notice
Copyright NVIDIA Corporation, 1999, 2000, 2001.
IP Status
NVIDIA Proprietary.
Version
NVIDIA date: January 18, 2001
$Date: 1999/06/21 13:54:17 $ $Revision: 1.2 $
$Id: //sw/main/docs/OpenGL/specs/GL_NV_texture_env_combine4.txt#14 $
Number
195
Dependencies
EXT_texture_env_combine is required and is modified by this extension
ARB_multitexture affects the definition of this extension
Overview
New texture environment function COMBINE4_NV allows programmable
texture combiner operations, including
ADD Arg0 * Arg1 + Arg2 * Arg3
ADD_SIGNED_EXT Arg0 * Arg1 + Arg2 * Arg3 - 0.5
where Arg0, Arg1, Arg2 and Arg3 are derived from
ZERO the value 0
PRIMARY_COLOR_EXT primary color of incoming fragment
TEXTURE texture color of corresponding texture unit
CONSTANT_EXT texture environment constant color
PREVIOUS_EXT result of previous texture environment; on
texture unit 0, this maps to PRIMARY_COLOR_EXT
TEXTURE<n>_ARB texture color of the <n>th texture unit
In addition, the result may be scaled by 1.0, 2.0 or 4.0.
Issues
None
None
Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, and
TexEnviv when the <pname> parameter value is TEXTURE_ENV_MODE
COMBINE4_NV 0x8503
Accepted by the <pname> parameter of GetTexEnvfv, GetTexEnviv,
TexEnvf, TexEnvi, TexEnvfv, and TexEnviv when the <target> parameter
value is TEXTURE_ENV
SOURCE3_RGB_NV 0x8583
SOURCE3_ALPHA_NV 0x858B
OPERAND3_RGB_NV 0x8593
OPERAND3_ALPHA_NV 0x859B
Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, and
TexEnviv when the <pname> parameter value is SOURCE0_RGB_EXT,
SOURCE1_RGB_EXT, SOURCE2_RGB_EXT, SOURCE3_RGB_NV, SOURCE0_ALPHA_EXT,
SOURCE1_ALPHA_EXT, SOURCE2_ALPHA_EXT, or SOURCE3_ALPHA_NV
ZERO
TEXTURE<n>_ARB
where <n> is in the range 0 to NUMBER_OF_TEXTURE_UNITS_ARB-1.
Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, and
TexEnviv when the <pname> parameter value is OPERAND0_RGB_EXT,
OPERAND1_RGB_EXT, OPERAND2_RGB_EXT or OPERAND3_RGB_NV
SRC_COLOR
ONE_MINUS_SRC_COLOR
SRC_ALPHA
ONE_MINUS_SRC_ALPHA
Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, and
TexEnviv when the <pname> parameter value is OPERAND0_ALPHA_EXT,
OPERAND1_ALPHA_EXT, OPERAND2_ALPHA_EXT, or OPERAND3_ALPHA_NV
SRC_ALPHA
ONE_MINUS_SRC_ALPHA
Additions to Chapter 2 of the OpenGL 1.2 Specification (OpenGL Operation)
None
Additions to Chapter 3 of the OpenGL 1.2 Specification (Rasterization)
Added to subsection 3.8.9, before the paragraph describing the state
requirements:
If the value of TEXTURE_ENV_MODE is COMBINE4_NV, the form of the
texture function depends on the values of COMBINE_RGB_EXT and
COMBINE_ALPHA_EXT, according to table 3.21. The RGB and ALPHA results
of the texture function are then multiplied by the values of
RGB_SCALE_EXT and ALPHA_SCALE, respectively. The results are clamped
to [0,1]. If the value of COMBINE_RGB_EXT or COMBINE_ALPHA_EXT is not
one of the listed values, the result is undefined.
COMBINE_RGB_EXT or
COMBINE_ALPHA_EXT Texture Function
------------------ ----------------
ADD Arg0 * Arg1 + Arg2 * Arg3
ADD_SIGNED_EXT Arg0 * Arg1 + Arg2 * Arg3 - 0.5
Table 3.21: COMBINE4_NV texture functions
The arguments Arg0, Arg1, Arg2 and Arg3 are determined by the values
of SOURCE<n>_RGB_EXT, SOURCE<n>_ALPHA_EXT, OPERAND<n>_RGB_EXT and
OPERAND<n>_ALPHA_EXT. In the following two tables, Ct and At are the
filtered texture RGB and alpha values; Cc and Ac are the texture
environment RGB and alpha values; Cf and Af are the RGB and alpha of
the primary color of the incoming fragment; and Cp and Ap are the RGB
and alpha values resulting from the previous texture environment. On
texture environment 0, Cp and Ap are identical to Cf and Af,
respectively. Ct<n> and At<n> are the filtered texture RGB and alpha
values from the texture bound to the <n>th texture unit. If the <n>th
texture unit is disabled, the value of each component is 1. The
relationship is described in tables 3.22 and 3.23.
SOURCE<n>_RGB_EXT OPERAND<n>_RGB_EXT Argument
----------------- -------------- --------
ZERO SRC_COLOR 0
ONE_MINUS_SRC_COLOR 1
SRC_ALPHA 0
ONE_MINUS_SRC_ALPHA 1
TEXTURE SRC_COLOR Ct
ONE_MINUS_SRC_COLOR (1-Ct)
SRC_ALPHA At
ONE_MINUS_SRC_ALPHA (1-At)
CONSTANT_EXT SRC_COLOR Cc
ONE_MINUS_SRC_COLOR (1-Cc)
SRC_ALPHA Ac
ONE_MINUS_SRC_ALPHA (1-Ac)
PRIMARY_COLOR_EXT SRC_COLOR Cf
ONE_MINUS_SRC_COLOR (1-Cf)
SRC_ALPHA Af
ONE_MINUS_SRC_ALPHA (1-Af)
PREVIOUS_EXT SRC_COLOR Cp
ONE_MINUS_SRC_COLOR (1-Cp)
SRC_ALPHA Ap
ONE_MINUS_SRC_ALPHA (1-Ap)
TEXTURE<n>_ARB SRC_COLOR Ct<n>
ONE_MINUS_SRC_COLOR (1-Ct<n>)
SRC_ALPHA At<n>
ONE_MINUS_SRC_ALPHA (1-At<n>)
Table 3.22: Arguments for COMBINE_RGB_EXT functions
SOURCE<n>_ALPHA_EXT OPERAND<n>_ALPHA_EXT Argument
----------------- -------------- --------
ZERO SRC_ALPHA 0
ONE_MINUS_SRC_ALPHA 1
TEXTURE SRC_ALPHA At
ONE_MINUS_SRC_ALPHA (1-At)
CONSTANT_EXT SRC_ALPHA Ac
ONE_MINUS_SRC_ALPHA (1-Ac)
PRIMARY_COLOR_EXT SRC_ALPHA Af
ONE_MINUS_SRC_ALPHA (1-Af)
PREVIOUS_EXT SRC_ALPHA Ap
ONE_MINUS_SRC_ALPHA (1-Ap)
TEXTURE<n>_ARB SRC_ALPHA At<n>
ONE_MINUS_SRC_ALPHA (1-At<n>)
Table 3.23: Arguments for COMBINE_ALPHA_EXT functions
Additions to Chapter 4 of the OpenGL 1.2 Specification (Per-Fragment Operations
and the Framebuffer)
None
Additions to Chapter 5 of the OpenGL 1.2 Specification (Special Functions)
None
Additions to Chapter 6 of the OpenGL 1.2 Specification (State and State Requests)
None
Additions to the AGL/GLX/WGL Specifications
None
GLX Protocol
None
Errors
INVALID_ENUM is generated if <params> value for SOURCE0_RGB_EXT,
SOURCE1_RGB_EXT, SOURCE2_RGB_EXT, SOURCE3_RGB_NV, SOURCE0_ALPHA_EXT,
SOURCE1_ALPHA_EXT, SOURCE2_ALPHA_EXT or SOURCE3_ALPHA_NV is not one of
ZERO, TEXTURE, CONSTANT_EXT, PRIMARY_COLOR_EXT, PREVIOUS_EXT or
TEXTURE<n>_ARB, where <n> is in the range 0 to
NUMBER_OF_TEXTURE_UNITS_ARB-1.
INVALID_ENUM is generated if <params> value for OPERAND0_RGB_EXT,
OPERAND1_RGB_EXT, OPERAND2_RGB_EXT or OPERAND3_RGB_NV is not one of
SRC_COLOR, ONE_MINUS_SRC_COLOR, SRC_ALPHA or ONE_MINUS_SRC_ALPHA.
INVALID_ENUM is generated if <params> value for OPERAND0_ALPHA_EXT
OPERAND1_ALPHA_EXT, OPERAND2_ALPHA_EXT, or OPERAND3_ALPHA_NV is not
one of SRC_ALPHA or ONE_MINUS_SRC_ALPHA.
Modifications to EXT_texture_env_combine
This extension relaxes the restrictions on SOURCE<n>_RGB_EXT,
SOURCE<n>_ALPHA_EXT, OPERAND<n>_RGB_EXT and OPERAND<n>_ALPHA_EXT for
use with EXT_texture_env_combine. All params specified by Table 3.22
and Table 3.23 are valid.
Dependencies on ARB_multitexture
If ARB_multitexture is not implemented, all references to
TEXTURE<n>_ARB and NUMBER_OF_TEXTURE_UNITS_ARB are deleted.
New State
Get Value Get Command Type Initial Value Attribute
--------- ----------- ---- ------------- ---------
SOURCE3_RGB_NV GetTexEnviv n x Z5+n ZERO texture
SOURCE3_ALPHA_NV GetTexEnviv n x Z5+n ZERO texture
OPERAND3_RGB_NV GetTexEnviv n x Z2 ONE_MINUS_SRC_COLOR texture
OPERAND3_ALPHA_NV GetTexEnviv n x Z2 ONE_MINUS_SRC_ALPHA texture
New Implementation Dependent State
None
NVIDIA Implementation Details
Because of a hardware limitation, TNT, TNT2, GeForce, and Quadro
treat "scale by 4.0" with the COMBINE_RGB_EXT or COMBINE_ALPHA_EXT
mode of ADD_SIGNED_EXT as "scale by 2.0".
Revision History
2/22/00 mjk - added NVIDIA Implementation Details
Implementation Support
List of OpenGL implementations supporting the GL_NV_texture_env_combine4 extension
Original File
Original text file for the GL_NV_texture_env_combine4 extension
Page generated on Sun Nov 20 18:39:12 2005