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GL_NV_register_combiners
NV_register_combiners
Name Strings
GL_NV_register_combiners
Contact
Mark J. Kilgard, NVIDIA Corporation (mjk 'at' nvidia.com)
Notice
Copyright NVIDIA Corporation, 1999, 2000, 2001, 2002, 2003.
IP Status
NVIDIA Proprietary.
Status
Shipping (version 1.6)
Version
NVIDIA Date: September 30, 2003 (version 1.6)
$Date$ $Revision$
$Id: //sw/main/docs/OpenGL/specs/GL_NV_register_combiners.txt#51 $
Number
191
Dependencies
ARB_multitexture, assuming the value of MAX_TEXTURE_UNITS_ARB is
at least 2.
Written based on the wording of the OpenGL 1.2 specification with
the ARB_multitexture appendix E.
NV_texture_shader affects the definition of this extension.
ARB_depth_texture and ARB_shadow -or- SGIX_depth_texture and
SGIX_shadow affect the definition of this extension.
Overview
NVIDIA's next-generation graphics processor and its derivative
designs support an extremely configurable mechanism know as "register
combiners" for computing fragment colors.
The register combiner mechanism is a significant redesign of NVIDIA's
original TNT combiner mechanism as introduced by NVIDIA's RIVA
TNT graphics processor. Familiarity with the TNT combiners will
help the reader appreciate the greatly enhanced register combiners
functionality (see the NV_texture_env_combine4 OpenGL extension
specification for this background). The register combiner mechanism
has the following enhanced functionality:
The numeric range of combiner computations is from [-1,1]
(instead of TNT's [0,1] numeric range),
The set of available combiner inputs is expanded to include the
secondary color, fog color, fog factor, and a second combiner
constant color (TNT's available combiner inputs consist of
only zero, a single combiner constant color, the primary color,
texture 0, texture 1, and, in the case of combiner 1, the result
of combiner 0).
Each combiner variable input can be independently scaled and
biased into several possible numeric ranges (TNT can only
complement combiner inputs).
Each combiner stage computes three distinct outputs (instead
TNT's single combiner output).
The output operations include support for computing dot products
(TNT has no support for computing dot products).
After each output operation, there is a configurable scale and bias
applied (TNT's combiner operations builds in a scale and/or bias
into some of its combiner operations).
Each input variable for each combiner stage is fetched from any
entry in a combiner register set. Moreover, the outputs of each
combiner stage are written into the register set of the subsequent
combiner stage (TNT could only use the result from combiner 0 as
a possible input to combiner 1; TNT lacks the notion of an
input/output register set).
The register combiner mechanism supports at least two general
combiner stages and then a special final combiner stage appropriate
for applying a color sum and fog computation (TNT provides two
simpler combiner stages, and TNT's color sum and fog stages are
hard-wired and not subsumed by the combiner mechanism as in register
combiners).
The register combiners fit into the OpenGL pipeline as a rasterization
processing stage operating in parallel to the traditional OpenGL
texture environment, color sum, AND fog application. Enabling this
extension bypasses OpenGL's existing texture environment, color
sum, and fog application processing and instead use the register
combiners. The combiner and texture environment state is orthogonal
so modifying combiner state does not change the traditional OpenGL
texture environment state and the texture environment state is
ignored when combiners are enabled.
OpenGL application developers can use the register combiner mechanism
for very sophisticated shading techniques. For example, an
approximation of Blinn's bump mapping technique can be achieved with
the combiner mechanism. Additionally, multi-pass shading models
that require several passes with unextended OpenGL 1.2 functionality
can be implemented in several fewer passes with register combiners.
Issues
Should we expose the full register combiners mechanism?
RESOLUTION: NO. We ignore small bits of NV10 hardware
functionality. The texture LOD input is ignored. We also ignore
the inverts on input to the EF product.
Do we provide full gets for all the combiner state?
RESOLUTION: YES.
Do we parameterize combiner input and output updates to avoid
enumerant explosions?
RESOLUTION: YES. To update a combiner stage input variable, you
need to specify the <stage>, <portion>, and <variable>. To update a
combiner stage output operation, you need to specify the <stage> and
<portion>. This does mean that we need to add special Get routines
that are likewise parameterized. Hence, GetCombinerInputParameter*,
GetCombinerOutputParameter*, and GetFinalCombinerInputParameter*.
Is the register combiner functionality a super-set of the TNT combiner
functionality?
Yes, but only in the sense of being a computational super-set.
All computations performed with the TNT combiners can be performed
with the register combiners, but the sequence of operations necessary
to configure an identical computational result can be quite
different.
For example, the TNT combiners have an operation that includes
a final complement operation. The register combiners can perform
range mappings only on inputs, but not on outputs. The register
combiners can mimic the TNT operation with a post-operation
complement only by taking pains to complement on input any uses
of the output in later combiner stages.
What this does mean is that NV10's hardware functionality
will permit support for both the NV_register_combiners AND
NV_texture_env_combine4 extensions.
Note the existance of an "speclit" input complement bit supported
by NV10 (but not accessible through the NV_register_combiners
extensions).
Should we say anything about the precision of the combiner
computations?
RESOLUTION: NO. The spec is written as if the computations are
done on floating point values ranging from -1.0 to 1.0 (clamping is
specified where this range is exceeded). The fact that NV10 does
the computations as 9-bit signed fixed point is not mentioned in
the spec. This permits a future design to support more precision
or use a floating pointing representation.
What should the initial combiner state be?
RESOLUTION: See tables NV_register_combiners.5 and
NV_register_combiners.6. The default state has one general combiner
stage active that modulates the incoming color with texture 0.
The final combiner is setup initially to implement OpenGL 1.2's
standard color sum and fog stages.
What should happen to the TEXTURE0_ARB and TEXTUER1_ARB inputs if
one or both textures are disabled?
RESOLUTION: The value of these inputs is undefined.
What do the TEXTURE0_ARB and TEXTURE1_ARB inputs correspond to?
Does the number correspond to the absolute texture unit number
or is the number based on how many textures are enabled (ie,
TEXTURE_ARB0 would correspond to the 2nd texture unit if the
2nd unit is enabled, but the 1st is disabled).
RESOLUTION: The absolute texture unit.
This should be a lot less confusing to the programmer than having
the texture inputs switch textures if texture 0 is disabled.
Note that the proposed hardware actually determines the TEXTURE0
and TEXTURE1 input based on which texture is enabled. This means
it is up to the ICD to properly update the combiner state when just
one texture is enabled. Since we will already have to do this to
track the standard OpenGL texture environment for ARB_multitexture,
we can do it for this extension too.
Should the combiners state be PushAttrib/PopAttrib'ed along with
the texture state?
RESOLUTION: YES.
Should we advertise the LOD fractional input to the combiners?
RESOLUTION: NO.
There will be a performance impact when two combiner stages are
enabled versus just one stage. Should we mention that somewhere?
RESOLUTION: NO. (But it is worth mentioning in this issues
section.)
Should the scale and bias for the CombinerOutputNV be indicated
by enumerants or specified outright as floats?
RESOLUTION: ENUMERANTS. While some future combiners might
support an arbitrary scale & bias specified as floats, NV10 just
does the enumerated options.
Should a dot product be computed in parralel with the sum of
products?
RESOLUTION: YES (changed for version 1.6). The hardware is
capable of summing the two dot products.
Versions of this specification prior to version 1.6 documented that
an INVALID_OPERATION should be generated if either <abDotProduct>
or <cdDotProduct> is true and then <sumOutput> is not GL_DISCARD.
However, this check was never added to the driver and some
applications found the mode useful.
void CombinerParameterfvNV(GLenum pname,
const GLfloat *params);
void CombinerParameterivNV(GLenum pname,
const GLint *params);
void CombinerParameterfNV(GLenum pname,
GLfloat param);
void CombinerParameteriNV(GLenum pname,
GLint param);
void CombinerInputNV(GLenum stage,
GLenum portion,
GLenum variable,
GLenum input,
GLenum mapping,
GLenum componentUsage);
void CombinerOutputNV(GLenum stage,
GLenum portion,
GLenum abOutput,
GLenum cdOutput,
GLenum sumOutput,
GLenum scale,
GLenum bias,
GLboolean abDotProduct,
GLboolean cdDotProduct,
GLboolean muxSum);
void FinalCombinerInputNV(GLenum variable,
GLenum input,
GLenum mapping,
GLenum componentUsage);
void GetCombinerInputParameterfvNV(GLenum stage,
GLenum portion,
GLenum variable,
GLenum pname,
GLfloat *params);
void GetCombinerInputParameterivNV(GLenum stage,
GLenum portion,
GLenum variable,
GLenum pname,
GLint *params);
void GetCombinerOutputParameterfvNV(GLenum stage,
GLenum portion,
GLenum pname,
GLfloat *params);
void GetCombinerOutputParameterivNV(GLenum stage,
GLenum portion,
GLenum pname,
GLint *params);
void GetFinalCombinerInputParameterfvNV(GLenum variable,
GLenum pname,
GLfloat *params);
void GetFinalCombinerInputParameterivNV(GLenum variable,
GLenum pname,
GLint *params);
Accepted by the <cap> parameter of Enable, Disable, and IsEnabled,
and by the <pname> parameter of GetBooleanv, GetIntegerv,
GetFloatv, and GetDoublev:
REGISTER_COMBINERS_NV 0x8522
Accepted by the <stage> parameter of CombinerInputNV,
CombinerOutputNV, GetCombinerInputParameterfvNV,
GetCombinerInputParameterivNV, GetCombinerOutputParameterfvNV,
and GetCombinerOutputParameterivNV:
COMBINER0_NV 0x8550
COMBINER1_NV 0x8551
COMBINER2_NV 0x8552
COMBINER3_NV 0x8553
COMBINER4_NV 0x8554
COMBINER5_NV 0x8555
COMBINER6_NV 0x8556
COMBINER7_NV 0x8557
Accepted by the <variable> parameter of CombinerInputNV,
GetCombinerInputParameterfvNV, and GetCombinerInputParameterivNV:
VARIABLE_A_NV 0x8523
VARIABLE_B_NV 0x8524
VARIABLE_C_NV 0x8525
VARIABLE_D_NV 0x8526
Accepted by the <variable> parameter of FinalCombinerInputNV,
GetFinalCombinerInputParameterfvNV, and
GetFinalCombinerInputParameterivNV:
VARIABLE_A_NV
VARIABLE_B_NV
VARIABLE_C_NV
VARIABLE_D_NV
VARIABLE_E_NV 0x8527
VARIABLE_F_NV 0x8528
VARIABLE_G_NV 0x8529
Accepted by the <input> parameter of CombinerInputNV:
ZERO (not new)
CONSTANT_COLOR0_NV 0x852A
CONSTANT_COLOR1_NV 0x852B
FOG (not new)
PRIMARY_COLOR_NV 0x852C
SECONDARY_COLOR_NV 0x852D
SPARE0_NV 0x852E
SPARE1_NV 0x852F
TEXTURE0_ARB (see ARB_multitexture)
TEXTURE1_ARB (see ARB_multitexture)
Accepted by the <mapping> parameter of CombinerInputNV:
UNSIGNED_IDENTITY_NV 0x8536
UNSIGNED_INVERT_NV 0x8537
EXPAND_NORMAL_NV 0x8538
EXPAND_NEGATE_NV 0x8539
HALF_BIAS_NORMAL_NV 0x853A
HALF_BIAS_NEGATE_NV 0x853B
SIGNED_IDENTITY_NV 0x853C
SIGNED_NEGATE_NV 0x853D
Accepted by the <input> parameter of FinalCombinerInputNV:
ZERO (not new)
CONSTANT_COLOR0_NV
CONSTANT_COLOR1_NV
FOG (not new)
PRIMARY_COLOR_NV
SECONDARY_COLOR_NV
SPARE0_NV
SPARE1_NV
TEXTURE0_ARB (see ARB_multitexture)
TEXTURE1_ARB (see ARB_multitexture)
E_TIMES_F_NV 0x8531
SPARE0_PLUS_SECONDARY_COLOR_NV 0x8532
Accepted by the <mapping> parameter of FinalCombinerInputNV:
UNSIGNED_IDENTITY_NV
UNSIGNED_INVERT_NV
Accepted by the <scale> parameter of CombinerOutputNV:
NONE (not new)
SCALE_BY_TWO_NV 0x853E
SCALE_BY_FOUR_NV 0x853F
SCALE_BY_ONE_HALF_NV 0x8540
Accepted by the <bias> parameter of CombinerOutputNV:
NONE (not new)
BIAS_BY_NEGATIVE_ONE_HALF_NV 0x8541
Accepted by the <abOutput>, <cdOutput>, and <sumOutput> parameter
of CombinerOutputNV:
DISCARD_NV 0x8530
PRIMARY_COLOR_NV
SECONDARY_COLOR_NV
SPARE0_NV
SPARE1_NV
TEXTURE0_ARB (see ARB_multitexture)
TEXTURE1_ARB (see ARB_multitexture)
Accepted by the <pname> parameter of GetCombinerInputParameterfvNV
and GetCombinerInputParameterivNV:
COMBINER_INPUT_NV 0x8542
COMBINER_MAPPING_NV 0x8543
COMBINER_COMPONENT_USAGE_NV 0x8544
Accepted by the <pname> parameter of GetCombinerOutputParameterfvNV
and GetCombinerOutputParameterivNV:
COMBINER_AB_DOT_PRODUCT_NV 0x8545
COMBINER_CD_DOT_PRODUCT_NV 0x8546
COMBINER_MUX_SUM_NV 0x8547
COMBINER_SCALE_NV 0x8548
COMBINER_BIAS_NV 0x8549
COMBINER_AB_OUTPUT_NV 0x854A
COMBINER_CD_OUTPUT_NV 0x854B
COMBINER_SUM_OUTPUT_NV 0x854C
Accepted by the <pname> parameter of CombinerParameterfvNV,
CombinerParameterivNV, GetBooleanv, GetDoublev, GetFloatv, and
GetIntegerv:
CONSTANT_COLOR0_NV
CONSTANT_COLOR1_NV
Accepted by the <pname> parameter of CombinerParameterfvNV,
CombinerParameterivNV, CombinerParameterfNV, CombinerParameteriNV,
GetBooleanv, GetDoublev, GetFloatv, and GetIntegerv:
NUM_GENERAL_COMBINERS_NV 0x854E
COLOR_SUM_CLAMP_NV 0x854F
Accepted by the <pname> parameter of GetFinalCombinerInputParameterfvNV
and GetFinalCombinerInputParameterivNV:
COMBINER_INPUT_NV
COMBINER_MAPPING_NV
COMBINER_COMPONENT_USAGE_NV
Accepted by the <pname> parameter of GetBooleanv, GetDoublev,
GetFloatv, and GetIntegerv:
MAX_GENERAL_COMBINERS_NV 0x854D
Additions to Chapter 2 of the 1.2 Specification (OpenGL Operation)
None
Additions to Chapter 3 of the 1.2 Specification (Rasterization)
-- Figure 3.1 "Rasterization" (page 58)
+ Change the "Texturing" block to say "Texture Fetching".
+ Insert a new block between "Texture Fetching" and "Color Sum".
Name the new block "Texture Environment Application".
+ Insert a new block after "Texture Fetching". Name the new block
"Register Combiners Application".
+ The output of the "Texture Fetching" stage feeds to both "Texture
Environment Application" and "Register Combiners Application".
+ The input for "Color Sum" comes from "Texture Environment
Application".
+ The output to "Fragments" is switched (controlled by
Disable/Enable REGISTER_COMBINERS_NV) between the output of "Fog"
and "Register Combiners Application".
Essentially, when register combiners are enabled, the entire standard
texture environment application, color sum, and fog blocks are
replaced with the single register combiners block. [Note that this
is different from how the NV_texture_env_combine4 extension works;
that extension controls the texture environment application
block, but still uses the standard color sum and fog blocks.]
-- NEW Section 3.8.12 "Register Combiners Application"
"In parallel to the texture application, color sum, and fog processes
described in sections 3.8.10, 3.9, and 3.10, register combiners
provide a means of computing fcoc, the final combiner output color,
for each fragment generated by rasterization.
The register combiners consist of two or more general combiner stages
arranged in a fixed sequence ordered by each combiner stage's number.
An implementation supports a maximum number of general combiners
stages, which may be queried by calling GetIntegerv with the symbolic
constant MAX_GENERAL_COMBINERS_NV. Implementations must
support at least two general combiner stages. The general combiner
stages are named COMBINER0_NV, COMBINER1_NV, and so on.
Each general combiner in the sequence receives its inputs and
computes its outputs in an identical manner. At the end of the
sequence of general combiner stages, there is a final combiner stage
that operates in a different manner than the general combiner stages.
The general combiner operation is described first, followed by a
description of the final combiner operation.
Each combiner stage (the general combiner stages and the final
combiner stage) has an associated combiner register set. Each
combiner register set contains <n> RGBA vectors with components
ranging from -1.0 to 1.0 where <n> is 8 plus the maximum number
of active textures supported (that is, the implementation's value
for MAX_TEXTURE_UNITS_ARB). The combiner register set entries
are listed in the table NV_register_combiners.1.
[ Table NV_register_combiners.1 ]
Initial Output
Register Name Value Reference Status
--------------------- ---------- ---------------- ---------
ZERO 0 - read only
CONSTANT_COLOR0_NV ccc0 Section 3.8.12.1 read only
CONSTANT_COLOR1_NV ccc1 Section 3.8.12.1 read only
FOG Cf Section 3.10 read only
PRIMARY_COLOR_NV cpri Section 2.13.1 read/write
SECONDARY_COLOR_NV csec Section 2.13.1 read/write
SPARE0_NV see below Section 3.8.12 read/write
SPARE1_NV undefined Section 3.8.12 read/write
TEXTURE0_ARB CT0 Figure E.2 read/write
TEXTURE1_ARB CT1 Figure E.2 read/write
TEXTURE<i>_ARB CT<i> Figure E.2 read/write
The register set of COMBINER0_NV, the first combiner stage,
is initialized as described in table NV_register_combiners.1.
The initial value of the alpha portion of register SECONDARY_COLOR_NV
is undefined. The initial value of the alpha portion of register
SPARE0_NV is the alpha component of texture 0 if texturing is
enabled for texture 0; however, the initial value of the RGB portion
SPARE0_NV is undefined. The initial value of the SPARE1_NV register
is undefined. The initial of registers TEXTURE0_ARB, TEXTURE1_ARB,
and TEXTURE<i>_ARB are undefined if texturing is not enabled for
textures 0, 1, and <i>, respectively.
The mapping of texture components to components of texture registers
is summarized in Table NV_register_combiners.2. In the following
table, At, Lt, It, Rt, Gt, Bt, and Dt, are the filtered texel
values.
[Table NV_register_combiners.2]: Correspondence of texture components
to register components for texture registers.
Base Internal Format RGB Values Alpha Value
-------------------- ---------- -----------
ALPHA 0, 0, 0 At
LUMINANCE Lt, Lt, Lt 1
LUMINANCE_ALPHA Lt, Lt, Lt At
INTENSITY It, It, It It
RGB Rt, Gt, Bt 1
RGBA Rt, Gt, Bt At
DEPTH_COMPONENT 0, 0, 0, Lt
(when TEXTURE_COMPARE_MODE_ARB is NONE -or-
TEXTURE_COMPARE_SGIX is false)
DEPTH_COMPONENT Lt, Lt, Lt, Lt
(when TEXTURE_COMPARE_MODE_ARB is COMPARE_R_TO_TEXTURE -or-
TEXTURE_COMPARE_SGIX is true)
HILO_NV 0, 0, 0, 0
DSDT_NV 0, 0, 0, 0
DSDT_MAG_NV 0, 0, 0, 0
DSDT_MAG_INTENSITY_NV 0, 0, 0, It
Note that the ALPHA, DEPTH_COMPONENT, and DSDT_MAG_INTENSITY_NV
base internal formats are mapped to components differently than
one could infer from the standard texture environment operations
with this formats. A texture's DEPTH_TEXTURE_MODE_ARB state (see
the ARB_depth_texture extension) is irrelevant for determining the
correspondence of texture components to register components for
texture registers when REGISTER_COMBINERS_NV is enabled.
3.8.12.1 Combiner Parameters
Combiner parameters are specified by
CombinerParameterfvNV(GLenum pname, const GLfloat *params);
CombinerParameterivNV(GLenum pname, const GLint *params);
CombinerParameterfNV(GLenum pname, GLfloat param);
CombinerParameteriNV(GLenum pname, GLint param);
<pname> is a symbolic constant indicating which parameter is to be
set as described in the table NV_register_combiners.3:
[ Table NV_register_combiners.3 ]
Number
Parameter Name of values Type
--------- ------------------------- --------- ---------------
ccc0 CONSTANT_COLOR0_NV 4 color
ccc1 CONSTANT_COLOR1_NV 4 color
ngc NUM_GENERAL_COMBINERS_NV 1 positive integer
csc COLOR_SUM_CLAMP_NV 1 boolean
<params> is a pointer to a group of values to which to set the
indicated parameter. <param> is simply the indicated parameter.
The number of values pointed to depends on the parameter being
set as shown in the table above. Color parameters specified with
CombinerParameter*NV are converted to floating-point values (if
specified as integers) as indicated by Table 2.6 for signed integers.
The floating-point color values are then clamped to the range [0,1].
The values ccc0 and ccc1 named by CONSTANT_COLOR0_NV and
CONSTANT_COLOR1_NV are constant colors available for inputs to the
combiner stages. The value ngc named by NUM_GENERAL_COMBINERS_NV
is a positive integer indicating how many general combiner stages are
active, that is, how many general combiner stages a fragment should
be processed by. Setting ngc to a value less than one or
greater than the value of MAX_GENERAL_COMBINERS_NV generates an
INVALID_VALUE error. The value csc named by COLOR_SUM_CLAMP_NV
is a boolean described in section 3.8.12.3.
3.8.12.2 General Combiner Stage Operation
The command
CombinerInputNV(GLenum stage,
GLenum portion,
GLenum variable,
GLenum input,
GLenum mapping,
GLenum componentUsage);
controls the assignment of all the general combiner input variables.
For the RGB combiner portion, these are Argb, Brgb, Crgb, and
Drgb; and for the combiner alpha portion, these are Aa, Ba, Ca,
and Da. The <stage> parameter is a symbolic constant of the form
COMBINER<i>_NV, indicating that general combiner stage <i> is to
be updated. The constant COMBINER<i>_NV = COMBINER0_NV + <i>
where <i> is in the range 0 to <k>-1 and <k> is the implementation
dependent value of MAX_COMBINERS_NV. The <portion> parameter
may be either RGB or ALPHA and determines whether the RGB color
vector or alpha scalar portion of the specified combiner stage is
updated. The <variable> parameter may be one of VARIABLE_A_NV,
VARIABLE_B_NV, VARIABLE_C_NV, or VARIABLE_D_NV and determines
which respective variable of the specified combiner stage and
combiner stage portion is updated.
The <input>, <mapping>, and <componentUsage> parameters specify
the assignment of a value for the input variable indicated by
<stage>, <portion>, and <variable>. The <input> parameter may be
one of the register names from table NV_register_combiners.1.
The <componentUsage> parameter may be one of RGB, ALPHA, or BLUE.
When the <portion> parameter is RGB, a <componentUsage> parameter
of RGB indicates that the RGB portion of the indicated register
should be assigned to the RGB portion of the combiner input variable,
while an ALPHA <componentUsage> parameter indicates that the
alpha portion of the indicated register should be replicated across
the RGB portion of the combiner input variable.
When the <portion> parameter is ALPHA, the <componentUsage>
parameter of ALPHA indicates that the alpha portion of the indicated
register should be assigned to the alpha portion of the combiner
input variable, while a BLUE <componentUsage> parameter indicates
that the blue component of the indicated register should be assigned
to the alpha portion of the combiner input variable.
When the <portion> parameter is ALPHA, a <componentUsage> parameter
of RGB generates an INVALID_OPERATION error. When the <portion>
parameter is RGB, a <componentUsage> parameter of BLUE generates
an INVALID_OPERATION error.
When the <componentUsage> parameter is ALPHA, an <input> parameter
of FOG generates an INVALID_OPERATION error. The alpha component of
the fog register is only available in the final combiner. The alpha
component of the fog register is the fragment's fog factor when fog
is enabled; otherwise, the alpha component of the fog register is
one.
Before the value in the register named by <input> is assigned to the
specified input variable, a range mapping is performed based on
<mapping>. The mapping may be one of the tokens from the table
NV_register_combiners.4.
[ Table NV_register_combiners.4 ]
Mapping Name Mapping Function
----------------------- -------------------------------------
UNSIGNED_IDENTITY_NV max(0.0, e)
UNSIGNED_INVERT_NV 1.0 - min(max(e, 0.0), 1.0)
EXPAND_NORMAL_NV 2.0 * max(0.0, e) - 1.0
EXPAND_NEGATE_NV -2.0 * max(0.0, e) + 1.0
HALF_BIAS_NORMAL_NV max(0.0, e) - 0.5
HALF_BIAS_NEGATE_NV -max(0.0, e) + 0.5
SIGNED_IDENTITY_NV e
SIGNED_NEGATE_NV -e
Based on the <mapping> parameter, the mapping function in the table
above is evaluated for each element <e> of the input vector before
assigning the result to the specified input variable. Note that
the mapping for the RGB and alpha portion of each input variable
is distinct.
Each general combiner stage computes the following ten expressions
based on the values assigned to the variables Argb, Brgb, Crgb,
Drgb, Aa, Ba, Ca, and Da as determined by the combiner state set
by CombinerInputNV.
["gcc" stands for general combiner computation.]
gcc1rgb = [ Argb[r]*Brgb[r], Argb[g]*Brgb[g], Argb[b]*Brgb[b] ]
gcc2rgb = [ Argb[r]*Brgb[r] + Argb[g]*Brgb[g] + Argb[b]*Brgb[b],
Argb[r]*Brgb[r] + Argb[g]*Brgb[g] + Argb[b]*Brgb[b],
Argb[r]*Brgb[r] + Argb[g]*Brgb[g] + Argb[b]*Brgb[b] ]
gcc3rgb = [ Crgb[r]*Drgb[r], Crgb[g]*Drgb[g], Crgb[b]*Drgb[b] ]
gcc4rgb = [ Crgb[r]*Drgb[r] + Crgb[g]*Drgb[g] + Crgb[b]*Drgb[b],
Crgb[r]*Drgb[r] + Crgb[g]*Drgb[g] + Crgb[b]*Drgb[b],
Crgb[r]*Drgb[r] + Crgb[g]*Drgb[g] + Crgb[b]*Drgb[b] ]
gcc5rgb = gcc1rgb + gcc3rgb
gcc6rgb = gcc1rgb or gcc3rgb [see below]
gcc1a = Aa * Ba
gcc2a = Ca * Da
gcc3a = gcc1a + gcc2a
gcc4a = gcc1a or gcc2a [see below]
The computation of gcc6rgb and gcc4a involves a special "or"
operation. This operation evaluates to the left-hand operand if
the alpha component of the combiner's SPARE0_NV register is less than
0.5; otherwise, the operation evaluates to the right-hand operand.
The command
CombinerOutputNV(GLenum stage,
GLenum portion,
GLenum abOutput,
GLenum cdOutput,
GLenum sumOutput,
GLenum scale,
GLenum bias,
GLboolean abDotProduct,
GLboolean cdDotProduct,
GLboolean muxSum);
controls the general combiner output operation including designating
the register set locations where results of the general combiner's
three computations are written. The <stage> and <portion>
parameters take the same values as the respective parameters for
CombinerInputNV.
If the <portion> parameter is ALPHA, specifying a non-FALSE value
for either of the parameters <abDotProduct> or <cdDotProduct>,
generates an INVALID_VALUE error.
The <scale> parameter must be one of NONE, SCALE_BY_TWO_NV,
SCALE_BY_FOUR_NV, or SCALE_BY_ONE_HALF_NV and specifies the
value of the combiner stage's portion scale, either cscalergb or
cscalea depending on the <portion> parameter, to 1.0, 2.0, 4.0,
or 0.5, respectively.
The <bias> parameter must be either NONE or
BIAS_BY_NEGATIVE_ONE_HALF_NV and specifies the value of the
combiner stage's portion bias, either cbiasrgb or cbiasa depending
on the <portion> parameter, to 0.0 or -0.5, respectively. If <scale>
is either SCALE_BY_ONE_HALF_NV or SCALE_BY_FOUR_NV, a <bias> of
BIAS_BY_NEGATIVE_ONE_HALF_NV generates an INVALID_OPERATION error.
If the <abDotProduct> parameter is FALSE, then
if <portion> is RGB, out1rgb = max(min(gcc1rgb + cbiasrgb) * cscalergb, 1), -1)
if <portion> is ALPHA, out1a = max(min((gcc1a + cbiasa) * cscalea, 1), -1)
otherwise <portion> must be RGB and
out1rgb = max(min((gcc2rgb + cbiasrgb) * cscalergb, 1), -1)
If the <cdDotProduct> parameter is FALSE, then
if <portion> is RGB, out2rgb = max(min((gcc3rgb + cbiasrgb) * cscalergb, 1), -1)
if <portion> is ALPHA, out2a = max(min((gcc2a + cbiasa) * cscalea, 1), -1)
otherwise <portion> must be RGB so
out2rgb = max(min((gcc4rgb + cbiasrgb) * cscalergb, 1), -1)
If the <muxSum> parameter is FALSE, then
if <portion> is RGB, out3rgb = max(min((gcc5rgb + cbiasrgb) * cscalergb, 1), -1)
if <portion> is ALPHA, out3a = max(min((gcc3a + cbiasa) * cscalea, 1), -1)
otherwise
if <portion> is RGB, out3rgb = max(min((gcc6rgb + cbiasrgb) * cscalergb, 1), -1)
if <portion> is ALPHA, out3a = max(min((gcc4a + cbiasa) * cscalea, 1), -1)
out1rgb, out2rgb, and out3rgb are written to the RGB portion of
combiner stage's registers named by <abOutput>, <cdOutput>, and
<sumOutput> respectively. out1a, out2a, and out3a are written to
the alpha portion of combiner stage's registers named by <abOutput>,
<cdOutput>, and <sumOutput> respectively. The parameters <abOutput>,
<cdOutput>, and <sumOutput> must be either DISCARD_NV or one of
the register names from table NV_register_combiners.1 that has an output
status of read/write. If an output is set to DISCARD_NV, that
output is not written to any register. The error INVALID_OPERATION
is generated if <abOutput>, <cdOutput>, and <sumOutput> do not all
name unique register names (though multiple outputs to DISCARD_NV
are legal).
When the general combiner stage's register set is written based on
the computed outputs, the updated register set is copied to the
register set of the subsequent combiner stage in the combiner
sequence. Copied undefined values are likewise undefined.
The subsequent combiner stage following the last active general
combiner stage, indicated by the general combiner stage's number
being equal to ngc-1, in the sequence is the final combiner
stage. In other words, the number of general combiner stages
each fragment is transformed by is determined by the value of
NUM_GENERAL_COMBINERS_NV.
3.8.12.3 Final Combiner Stage Operation
The final combiner stage operates differently from the general
combiner stages. While a general combiner stage updates its register
set and passes the register set to the next combiner stage, the final
combiner outputs an RGBA color fcoc, the final combiner output color.
The final combiner stage is capable of applying the standard OpenGL
color sum and fog operations, but has the configurability to be
used for other purposes.
The command
FinalCombinerInputNV(GLenum variable,
GLenum input,
GLenum mapping,
GLenum componentUsage);
controls the assignment of all the final combiner input variables.
The variables A, B, C, D, E, and F are RGB vectors. The variable
G is an alpha scalar. The <variable> parameter may be one of
VARIABLE_A_NV, VARIABLE_B_NV, VARIABLE_C_NV, VARIABLE_D_NV,
VARIABLE_E_NV, VARIABLE_F_NV, and VARIABLE_G_NV, and determines
which respective variable of the final combiner stage is updated.
The <input>, <mapping>, and <componentUsage> parameters specify
the assignment of a value for the input variable indicated by
<variable>.
The <input> parameter may be any one of the register names from
table NV_register_combiners.1 or be one of two pseudo-register
names, either E_TIMES_F_NV or SPARE0_PLUS_SECONDARY_COLOR_NV.
The value of E_TIMES_F_NV is the product of the value of
variable E times the value of variable F. The value of
SPARE0_PLUS_SECONDARY_COLOR_NV is the value the SPARE0_NV
register mapped using the UNSIGNED_IDENITY_NV input mapping plus
the value of the SECONDARY_COLOR_NV register mapped using the
UNSIGNED_IDENTITY_NV input mapping. If csc, the color sum clamp,
is non-FALSE, the value of SPARE0_PLUS_SECONDARY_COLOR_NV is first
clamped to the range [0,1]. The alpha component of E_TIMES_F_NV
and SPARE0_PLUS_SECONDARY_COLOR_NV is always zero.
When <variable> is one of VARIABLE_E_NV, VARIABLE_F_NV,
or VARIABLE_G_NV and <input> is either E_TIMES_F_NV or
SPARE0_PLUS_SECONDARY_COLOR_NV, generate an INVALID_OPERATION
error. When <variable> is VARIABLE_A_NV and <input> is
SPARE0_PLUS_SECONDARY_COLOR_NV, generate an INVALID_OPERATION
error.
The <componentUsage> parameter may be one of RGB, BLUE, ALPHA
(with certain restrictions depending on the <variable> and <input>
as described below).
When the <variable> parameter is not VARIABLE_G_NV, a
<componentUsage> parameter of RGB indicates that the RGB portion of
the indicated register should be assigned to the RGB portion of the
combiner input variable, while an ALPHA <componentUsage> parameter
indicates that the alpha portion of the indicated register should
be replicated across the RGB portion of the combiner input variable.
When the <variable> parameter is VARIABLE_G_NV, a <componentUsage>
parameter of ALPHA indicates that the alpha component of the
indicated register should be assigned to the alpha portion of the
G input variable, while a BLUE <componentUsage> parameter indicates
that the blue component of the indicated register should be assigned
to the alpha portion of the G input variable.
The INVALID_OPERATION error is generated when <componentUsage> is
BLUE and <variable> is not VARIABLE_G_NV. The INVALID_OPERATION
error is generated when <componentUsage> is RGB and <variable>
is VARIABLE_G_NV.
The INVALID_OPERATION error is generated when both the <input>
parameter is either E_TIMES_F_NV or SPARE0_PLUS_SECONDARY_COLOR_NV
and the <componentUsage> parameter is ALPHA or BLUE.
Before the value in the register named by <input> is assigned to
the specified input variable, a range mapping is performed based
on <mapping>. The mapping may be either UNSIGNED_IDENTITY_NV
or UNSIGNED_INVERT_NV and operates as specified in table
NV_register_combiners.4.
The final combiner stage computes the following expression based
on the values assigned to the variables A, B, C, D, E, F, and G as
determined by the combiner state set by FinalCombinerInputNV
fcoc = [ min(ab[r] + iac[r] + D[r], 1.0),
min(ab[g] + iac[g] + D[g], 1.0),
min(ab[b] + iac[b] + D[b], 1.0),
G ]
where
ab = [ A[r]*B[r], A[g]*B[g], A[b]*B[b] ]
iac = [ (1.0 -A [r])*C[r], (1.0 - A[g])*C[g], (1.0 - A[b])*C[b] ]
3.8.12.4 Required State
The state required for the register combiners is a bit indicating
whether register combiners are enabled or disabled, an integer
indicating how many general combiners are active, a bit indicating
whether or not the color sum clamp to 1 should be performed, two
RGBA constant colors, <n> sets of general combiner stage state where
<n> is the value of MAX_GENERAL_COMBINERS_NV, and the final
combiner stage state. The per-stage general combiner state consists
of the RGB input portion state and the alpha input portion state.
Each portion (RGB and alpha) of the per-stage general combiner
state consists of: four integers indicating the input register for
the four variables A, B, C, and D; four integers to indicate each
variable's range mapping; four bits to indicate whether to use the
alpha component of the input for each variable; a bit indicating
whether the AB dot product should be output; a bit indicating
whether the CD dot product should be output; a bit indicating
whether the sum or mux output should be output; two integers to
maintain the output scale and bias enumerants; three integers to
maintain the output register set names. The final combiner stage
state consists of seven integers to indicate the input register
for the seven variables A, B, C, D, E, F, and G; seven integers to
indicate each variable's range mapping; and seven bits to indicate
whether to use the alpha component of the input for each variable.
The general combiner per-stage state is initialized as described
in table NV_register_combiners.5.
[ Table NV_register_combiners.5 ]
Component
Portion Variable Input Usage Mapping
------- -------- ------------------ --------- ----------------------
RGB A PRIMARY_COLOR_NV RGB UNSIGNED_IDENTITY_NV
RGB B ZERO RGB UNSIGNED_INVERT_NV
RGB C ZERO RGB UNSIGNED_IDENTITY_NV
RGB D ZERO RGB UNSIGNED_IDENTITY_NV
alpha A PRIMARY_COLOR_NV ALPHA UNSIGNED_IDENTITY_NV
alpha B ZERO ALPHA UNSIGNED_INVERT_NV
alpha C ZERO ALPHA UNSIGNED_IDENTITY_NV
alpha D ZERO ALPHA UNSIGNED_IDENTITY_NV
The final combiner stage state is initialized as described in table
NV_register_combiners.6.
[ Table NV_register_combiners.6 ]
Component
Variable Input Usage Mapping
-------- -------------------------------- --------- ----------------------
A FOG ALPHA UNSIGNED_IDENTITY_NV
B SPARE0_PLUS_SECONDARY_COLOR_NV RGB UNSIGNED_IDENTITY_NV
C FOG RGB UNSIGNED_IDENTITY_NV
D ZERO RGB UNSIGNED_IDENTITY_NV
E ZERO RGB UNSIGNED_IDENTITY_NV
F ZERO RGB UNSIGNED_IDENTITY_NV
G SPARE0_NV ALPHA UNSIGNED_IDENTITY_NV"
-- NEW Section 3.8.11 "Antialiasing Application"
Insert the following paragraph BEFORE the section's first paragraph:
"Register combiners are enabled or disabled using the generic Enable
and Disable commands, respectively, with the symbolic constant
REGISTER_COMBINERS_NV. If the register combiners are enabled (and not in color
index mode), the fragment's color value is replaced with fcoc, the
final combiner output color, computed in section 3.8.12; otherwise,
the fragment's color value is the result of the fog application
in section 3.10."
Additions to Chapter 4 of the 1.2 Specification (Per-Fragment Operations
and the Frame Buffer)
None
Additions to Chapter 5 of the 1.2 Specification (Special Functions)
None
Additions to Chapter 6 of the 1.2 Specification (State and State Requests)
-- Section 6.1.3 "Enumerated Queries"
Change the first two sentences (page 182) to say:
"Other commands exist to obtain state variables that are identified by
a category (clip plane, light, material, combiners, etc.) as well as
a symbolic constant. These are"
Add to the bottom of the list of function prototypes (page 183):
void GetCombinerInputParameterfvNV(GLenum stage, GLenum portion, GLenum variable,
GLenum pname, const GLfloat *params);
void GetCombinerInputParameterivNV(GLenum stage, GLenum portion, GLenum variable,
GLenum pname, const GLint *params);
void GetCombinerOutputParameterfvNV(GLenum stage, GLenum portion, GLenum pname, const GLfloat *params);
void GetCombinerOutputParameterivNV(GLenum stage, GLenum portion, GLenum pname, GLint *params);
void GetFinalCombinerInputParameterfvNV(GLenum variable, GLenum pname, const GLfloat *params);
void GetFinalCombinerInputParameterivNV(GLenum variable, GLenum pname, const GLfloat *params);
Add the following paragraph to the end of the section (page 184):
"The GetCombinerInputParameterfvNV,
GetCombinerInputParameterivNV, GetCombinerOutputParameterfvNV,
and GetCombinerOutputParameterivNV parameter <stage> may be one of
COMBINER0_NV, COMBINER1_NV, and so on, indicating which general
combiner stage to query. The GetCombinerInputParameterfvNV,
GetCombinerInputParameterivNV, GetCombinerOutputParameterfvNV,
and GetCombinerOutputParameterivNV parameter <portion> may be
either RGB or ALPHA, indicating which portion of the general
combiner stage to query. The GetCombinerInputParameterfvNV
and GetCombinerInputParameterivNV parameter <variable> may
be one of VARIABLE_A_NV, VARIABLE_B_NV, VARIABLE_C_NV,
or VARIABLE_D_NV, indicating which variable of the general
combiner stage to query. The GetFinalCombinerInputParameterfvNV
and GetFinalCombinerInputParameterivNV parameter <variable> may be one
of VARIABLE_A_NV, VARIABLE_B_NV, VARIABLE_C_NV, VARIABLE_D_NV,
VARIABLE_E_NV, VARIABLE_F_NV, or VARIABLE_G_NV."
Additions to the GLX Specification
None.
GLX Protocol
Thirteen new GL commands are added.
The following seven rendering commands are sent to the sever as part
of a glXRender request:
CombinerParameterfNV
2 12 rendering command length
2 4136 rendering command opcode
4 ENUM pname
4 FLOAT32 param
CombinerParameterfvNV
2 8+4*n rendering command length
2 4137 rendering command opcode
4 ENUM pname
0x852A n=4 GL_CONSANT_COLOR0_NV
0x852B n=4 GL_CONSANT_COLOR1_NV
0x854E n=1 GL_NUM_GENERAL_COMBINERS_NV
0x854F n=1 GL_COLOR_SUM_CLAMP_NV
else n=0
4*n LISTofFLOAT32 params
CombinerParameteriNV
2 12 rendering command length
2 4138 rendering command opcode
4 ENUM pname
4 INT32 param
CombinerParameterivNV
2 8+4*n rendering command length
2 4139 rendering command opcode
4 ENUM pname
0x852A n=4 GL_CONSANT_COLOR0_NV
0x852B n=4 GL_CONSANT_COLOR1_NV
0x854E n=1 GL_NUM_GENERAL_COMBINERS_NV
0x854F n=1 GL_COLOR_SUM_CLAMP_NV
else n=0
4*n LISTofINT32 params
CombinerInputNV
2 28 rendering command length
2 4140 rendering command opcode
4 ENUM stage
4 ENUM portion
4 ENUM variable
4 ENUM input
4 ENUM mapping
4 ENUM componentUsage
CombinerOutputNV
2 36 rendering command length
2 4141 rendering command opcode
4 ENUM stage
4 ENUM portion
4 ENUM abOutput
4 ENUM cdOutput
4 ENUM sumOutput
4 ENUM scale
4 ENUM bias
1 BOOL abDotProduct
1 BOOL cdDotProduct
1 BOOL muxSum
1 BOOL unused
FinalCombinerInputNV
2 20 rendering command length
2 4142 rendering command opcode
4 ENUM variable
4 ENUM input
4 ENUM mapping
4 ENUM componentUsage
The remaining six commands are non-rendering commands. These commands
are sent separately (i.e., not as part of a glXRender or glXRenderLarge
request), using the glXVendorPrivateWithReply request:
GetCombinerInputParameterfvNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 7 request length
4 1270 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM stage
4 ENUM portion
4 ENUM variable
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 FLOAT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofFLOAT32 params
GetCombinerInputParameterivNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 7 request length
4 1271 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM stage
4 ENUM portion
4 ENUM variable
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 INT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofINT32 params
GetCombinerOutputParameterfvNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 6 request length
4 1272 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM stage
4 ENUM portion
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 FLOAT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofFLOAT32 params
GetCombinerOutputParameterivNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 6 request length
4 1273 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM stage
4 ENUM portion
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 INT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofINT32 params
GetFinalCombinerInputParameterfvNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 5 request length
4 1274 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM variable
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 FLOAT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofFLOAT32 params
GetFinalCombinerInputParameterivNV
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 5 request length
4 1275 vendor specific opcode
4 GLX_CONTEXT_TAG context tag
4 ENUM variable
4 ENUM pname
=>
1 1 reply
1 unused
2 CARD16 sequence number
4 m reply length, m = (n==1 ? 0 : n)
4 unused
4 CARD32 unused
if (n=1) this follows:
4 INT32 params
12 unused
otherwise this follows:
16 unused
n*4 LISTofINT32 params
Dependencies on NV_texture_shader
If NV_texture_shader is not supported, references to HILO_NV,
DSDT_NV, DSDT_MAG_NV, and DSDT_MAG_INTENSITY_NV base internal
formats in this document are invalid and should be ignored.
Dependencies on ARB_depth_texture and ARB_shadow -or- SGIX_depth_texture
and SGIX_shadow
If ARB_depth_texture and ARB_shadow -or- SGIX_depth_texture and
SGIX_shadow are not supported, references to the DEPTH_COMPONENT base
internal format in this document are invalid and should be ignored.
If ARB_depth_texture and ARB_shadow are not supported, references
to the DEPTH_TEXTURE_MODE_ARB state in this document are invalid
and should be ignored.
Errors
INVALID_VALUE is generated when CombinerParameterfvNV
or CombinerParameterivNV is called with <pname> set to
NUM_GENERAL_COMBINERS and the value pointed to by <params>
is less than one or greater or equal to the value of
MAX_GENERAL_COMBINERS_NV.
INVALID_OPERATION is generated when CombinerInputNV is called
with a <componentUsage> parameter of RGB and a <portion> parameter
of ALPHA.
INVALID_OPERATION is generated when CombinerInputNV is called
with a <componentUsage> parameter of BLUE and a <portion> parameter
of RGB.
INVALID_OPERATION is generated When CombinerInputNV is called with a
<componentUsage> parameter of ALPHA and an <input> parameter of FOG.
INVALID_VALUE is generated when CombinerOutputNV is called with
a <portion> parameter of ALPHA, but a non-FALSE value for either
of the parameters <abDotProduct> or <cdDotProduct>.
INVALID_OPERATION is generated when CombinerOutputNV is called with
a <scale> of either SCALE_BY_ONE_HALF_NV or SCALE_BY_FOUR_NV and
a <bias> of BIAS_BY_NEGATIVE_ONE_HALF_NV.
INVALID_OPERATION is generated when CombinerOutputNV is called such
that <abOutput>, <cdOutput>, and <sumOutput> do not all name unique
register names (though multiple outputs to DISCARD_NV are legal).
INVALID_OPERATION is generated when FinalCombinerInputNV
is called where <variable> is one of VARIABLE_E_NV,
VARIABLE_F_NV, or VARIABLE_G_NV and <input> is E_TIMES_F_NV or
SPARE0_PLUS_SECONDARY_COLOR_NV.
INVALID_OPERATION is generated when FinalCombinerInputNV
is called where <variable> is VARIABLE_A_NV and <input> is
SPARE0_PLUS_SECONDARY_COLOR_NV.
INVALID_OPERATION is generated when FinalCombinerInputNV is called
with VARIABLE_G_NV for <variable> and RGB for <componentUsage>.
INVALID_OPERATION is generated when FinalCombinerInputNV is called
with a value other than VARIABLE_G_NV for <variable> and BLUE for
<componentUsage>.
INVALID_OPERATION is generated when FinalCombinerInputNV is
called where the <input> parameter is either E_TIMES_F_NV or
SPARE0_PLUS_SECONDARY_COLOR_NV and the <componentUsage> parameter
is ALPHA.
New State
-- (NEW table 6.29, after p217)
Get Value Type Get Command Initial Value Description Sec Attribute
--------- -------- ---------------------------------- ---------------------- ---------------- -------- --------------
REGISTER_COMBINERS_NV B IsEnabled False register 3.8.11 texture/enable
combiners enable
NUM_GENERAL_COMBINERS_NV Z+ GetIntegerv 1 number of active 3.8.12.1 texture
combiner stages
COLOR_SUM_CLAMP_NV B GetBooleanv True whether or not 3.8.12.1 texture
SPARE0_PLUS_
SECONDARY_
COLOR_NV clamps
combiner stages
CONSTANT_COLOR0_NV C GetFloatv 0,0,0,0 combiner constant 3.8.12.1 texture
color zero
CONSTANT_COLOR1_NV C GetFloatv 0,0,0,0 combiner constant 3.8.12.1 texture
color one
COMBINER_INPUT_NV Z8x#x2x4 GetCombinerInputParameter*NV see 3.8.12.4 combiner input 3.8.12.2 texture
variables
COMBINER_COMPONENT_USAGE_NV Z3x#x2x4 GetCombinerInputParameter*NV see 3.8.12.4 use alpha for 3.8.12.2 texture
combiner input
COMBINER_MAPPING_NV Z8x#x2x4 GetCombinerInputParameter*NV see 3.8.12.4 complement 3.8.12.2 texture
combiner input
COMBINER_AB_DOT_PRODUCT_NV Bx#x2 GetCombinerOutputParameter*NV False output AB dot 3.8.12.3 texture
product
COMBINER_CD_DOT_PRODUCT_NV Bx#x2 GetCombinerOutputParameter*NV False output CD dot 3.8.12.3 texture
product
COMBINER_MUX_SUM_NV Bx#x2 GetCombinerOutputParameter*NV False output mux sum 3.8.12.3 texture
COMBINER_SCALE_NV Z2x#x2 GetCombinerOutputParameter*NV NONE output scale 3.8.12.3 texture
COMBINER_BIAS_NV Z2x#x2 GetCombinerOutputParameter*NV NONE output bias 3.8.12.3 texture
COMBINER_AB_OUTPUT_NV Z7x#x2 GetCombinerOutputParameter*NV DISCARD_NV AB output 3.8.12.3 texture
register
COMBINER_CD_OUTPUT_NV Z7x#x2 GetCombinerOutputParameter*NV DISCARD_NV CD output 3.8.12.3 texture
register
COMBINER_SUM_OUTPUT_NV Z7x#x2 GetCombinerOutputParameter*NV SPARE0_NV sum output 3.8.12.3 texture
register
COMBINER_INPUT_NV Z10x7 GetFinalCombinerInputParameter*NV see 3.8.12.4 final combiner 3.8.12.4 texture
input
COMBINER_MAPPING_NV Z2x7 GetFinalCombinerInputParameter*NV UNSIGNED_IDENTITY_NV final combiner 3.8.12.4 texture
input mapping
COMBINER_COMPONENT_USAGE_NV Z2x7 GetFinalCombinerInputParameter*NV see 3.8.12.4 use alpha for 3.8.12.4 texture
final combiner
input mapping
[ where # is the value of MAX_GENERAL_COMBINERS_NV ]
New Implementation Dependent State
(table 6.24, p214) add the following entry:
Get Value Type Get Command Minimum Value Description Sec Attribute
-------------------------- ---- ----------- ------------- ---------------- ------ --------------
MAX_GENERAL_COMBINERS_NV Z+ GetIntegerv 2 Maximum num of 3.8.12 -
general combiner
NVIDIA Implementation Details
The effective range of the RGB portion of the final combiner should
be [0,4] if the color sum clamp is false. Exercising this range
requires assigning SPARE0_PLUS_SECONDARY_COLOR_NV to the D variable
and either B or C or both B and C. In practice this is a very
unlikely configuration.
However due to a bug in the GeForce 256 and Quadro hardware, values
generated above 2 in the RGB portion of the final combiner will be
computed incorrectly. GeForce2 GTS and subsequent NVIDIA GPUs have
fixed this bug.
The behavior of the SIGNED_NEGATE_NV mapping mode is undefined on
GeForce3 GPUs (NV20) when used to map the initial value of a texture
register corresponding to an enabled texture with a base internal
format of GL_DEPTH_COMPONENT and a GL_TEXTURE_COMPARE_MODE_ARB mode of
GL_COMPARE_R_TO_TEXTURE (or for SGIX_shadow, GL_TEXTURE_COMPARE_SGIX
mode of true) mode when multiple enabled textures have different
values for GL_TEXTURE_COMPARE_FUNC_ARB (or for SGIX_shadow,
GL_TEXTURE_COMPARE_OPERATOR_SGIX). Values subsequently assigned
to such registers and then mapped with SIGNED_NEGATIE_NV operate
as expected. This issue does not affect GeForce4 Ti (NV25) and
subsequent GPUs.
Revision History
April 4, 2000 - Document that alpha component of the FOG register
should be zero when fog is disabled. The Release 4 NVIDIA drivers
have a bug where this is not always true (though it often still is).
The bug is fixed in the Release 5 NVIDIA drivers.
June 8, 2000 - The alpha component of the FOG register is not
available for use until the final combiner. The specification
previously incorrectly stated:
"INVALID_OPERATION is generated When CombinerInputNV is called with
a <portion> parameter of ALPHA and an <input> parameter of FOG."
It is actually the <componentUsage> (not the <portion>) that should
not be allowed to be ALPHA. The Release 4 NVIDIA drivers implemented
the above incorrect error check. The Release 5 (and later) NVIDIA
drivers (after June 8, 2000) have fixed this bug and correctly
implement the error based on <componentUsage>.
The specification previously did not allow BLUE for the
<componentUsage> of the G variable in the final combiner. This is
now allowed in the Release 5 (and later) NVIDIA drivers (after June
8, 2000). The Release 4 NVIDIA drivers do not permit BLUE for the
<componentUsage> of the G variable and generate an INVALID_OPERATION
error if this is attempted. The Release 5 NVIDIA drivers (after June
8, 2000) have fixed this bug and permit BLUE for the <componentUsage>
of the G variable.
August 11, 2000 - The "mux" operation was incorrectly documented in
previous versions of this specification. The correct mux behave is
as follows:
spare0_alpha >= 0.5 ? C*D : A*B
or
spare0_alpha < 0.5 ? A*B : C*D
Previous versions of this specification had the mux sense reversed.
October 31, 2000 - The initial general combiner state
was misdocumented for the B variable. Previously, Table
NV_register_combiners.5 said that the RGB and alpha inputs for B
were GL_TEXTURE#_ARB and the RGB and alpha input mappings for B
were GL_UNSIGNED_IDENTITY_NV. The table is now updated so that the
RGB and alpha inputs for B are GL_ZERO and the RGB and alpha input
mappings for B are GL_UNSIGNED_INVERT_NV. The implementation has
always behaved in the manner described by the updated specification.
December 13, 2000 - Added a new table NV_register_combiners.2
describing the correspondence of texture components to register
components for texture registers. This table is based on the
table in the EXT_texture_env_combine extension. The table includes
correspondences for HILO, DSDT, DSDT_MAG, DSDT_MAG_INTENSITY, and
DEPTH_COMPONENT formatted textures when supported in conjunction
with the NV_texture_shader, SGIX_depth_texture, and SGIX_shadow
extensions.
Because a new table 2 was inserted, all the tables beyond it are
renumbered.
Document the behavior of SIGNED_NEGATE_NV in conjunction with shadow
mapping in the "NVIDIA Implementation Details" section.
June 28, 2002 - Properly document NV_register_combiners interactions
with the ARB_depth_texture and ARB_shadow extensions (previously,
the extension just addressed the SGIX versions of these extensions).
September 30, 2003 - Remove an error (not implemented in early NVIDIA
drivers prior to Release 4x.xx drivers; implemented in Relase
4x.xx drivers; and again removed for Release 5x.xx drivers and up)
that was meant to restrict the API to not allow the summing of dot
product outputs. NVIDIA hardware handles this case correctly however
so the functionality might as well be supported; some applications
found it useful. The deleted error read:
If the <abDotProduct> or <cdDotProduct> parameter is non-FALSE,
the value of the <sumOutput> parameter must be GL_DISCARD_NV;
otherwise, generate an INVALID_OPERATION error.
Implementation Support
List of OpenGL implementations supporting the GL_NV_register_combiners extension
Original File
Original text file for the GL_NV_register_combiners extension
Page generated on Sun Nov 20 18:39:10 2005