geforce 256 and riva tnt combiners -...

11/02/1999

Copyright NVIDIA Corporation, 1999. NVIDIA Proprietary.

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GeForce 256 and RIVA TNT Combiners

How to best utilize the per-pixel operations using OpenGL on NVIDIA Graphics Processors

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PointRasterization

LineRasterization

PolygonRasterization

Pixel RectangleRasterization

BitmapRasterization

FromPrimitiveAssembly

DrawPixels

Bitmap

TextureFetching

TextureEnvironmentApplication

Color Sum

FogTo fragmentprocessing

NVIDIA OpenGL Combiners(see Figure 3.1 of OpenGL 1.2 spec)

CoverageApplication

RegisterCombiners

Texture Unit 0

General Stage 1

Final Stage

Texture Unit 1

General Stage 0

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Which Texture Environment orCombiner Extension to use?

•Base OpenGL texture environment•supports modulate, replace, blend, decal•all OpenGL implementation support this

• EXT_texture_env_add•supports add•widely supported extension, but not guaranteed

•EXT_texture_env_combine•supports AB+C, AB+(1-A)C•additional scale & bias capability•user-defined constant•multi-vendor extension (NVIDIA & ATI)

•NV_texture_env_combine4•supports AB+CD, generalizes EXT_texture_env_combine•TNT & later NVIDIA graphics processors

•NV_register_combiners•register model, non-linear data flow•signed math, input mappings, multiple dot products•subsumes texture environment, color sum, & fog stages•additional inputs: fog color & factor, & secondary color•number of stages independent of active textures•GeForce & future NVIDIA graphics processors (not TNT)

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zeroconstant color

primary colortexture 0

texture 1A × B + C × D

A × B + C × D

combiner 0 resultzero

constant colorprimary color

texture 0texture 1

NV_texture_env_combine4

TextureUnit 0

TextureUnit 1

combiner inputs (RGBA)

post-combiner color (RGBA)

zeroconstant color

primary colortexture 0

texture 1A × B + C × D

A × B + C × D

combiner 0 resultzero

constant colorprimary color

texture 0texture 1

RRGGBB portionportion

Alphaportionportion

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NV_register_combinersFunctional Overview

•overrides texture stages/environment, color sum, and fog in current APIs

•signed math (negative one to positive range)•extended range through scaling

•dot products for lighting and image processing applications•specially designed for specular, diffuse, and ambient per-pixel lighting•object space bump map lighting•tangent space bump map lighting•non-photorealistic lighting models•post-filtering 3x3 color matrix for color space conversions

•register model supports non-linear data flows•superior to linear chain in current APIs

•effectively, a VLIW instruction set for fragment coloring

•very efficient hardware implementation

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NV_register_combinersExamples

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NV_register_combinersRegister Combiner Operational Overview

generalcombiner

stages

final combiner

RGB Portion Alpha Portioninitializeregisters

stage #0

stage #1(optional)

AB+CD, AB, CD

AB+CD, AB, CD

AB+CD, AB, CD

AB+CD, AB, CD

AB+(1-A)C+D, EF, G RGBA fragment

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NV_register_combinersRegister Set

•primary (diffuse) color•initialized to RGBA of fragment’s primary color

•secondary (specular) color•initialized to RGB of fragment’s secondary color•alpha initially undefined

•texture 0 & texture 1•initialized to fragment’s filtered RGBA texel from numbered texture unit•undefined if numbered texture unit is disabled

•spare 0 & spare 1•initially undefined

•fog•RGB is current fog color•Alpha is fragment’s fog factor (only available in final combiner)•read-only

•constant color 0 & constant color 1•initialized to user-defined RGBA value•read-only

•zero•constant, read-only value of zero

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NV_register_combiners

zero

primary color

secondary color

constant color 0

constant color 1

fog

spare 1

spare 0

texture 0

texture 1

A B + C D

A B mux C D

-or-

A B

A • B

-or-

C • D

C D

-or-

A B C D

inputmap

inputmap

inputmap

not writeable

RGB A RGB A

input registers

computations

output registers

General Combiner Operation, RGB portion

scaleandbias

inputmap

not readable

written output registers mustbe mutually exclusive

zero

primary color

secondary color

constant color 0

constant color 1

fog

spare 1

spare 0

texture 0

texture 1

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NV_register_combinersGeneral Combiner Stage RGB Computations

A = (Ar, Ag, Ab) B = (Br, Bg, Bb) C = (Cr, Cg, Cb) D = (Dr, Dg, Db)

A B C D

(Ar Br, Ag Bg, Ab Bb) (Cr Dr, Cg Dg, Cb Db)

A B + C D A B mux C DA • B C • D

AB output ABCD output CD output

(Ar Br + Ag Bg + Ab Bb,Ar Br + Ag Bg + Ab Bb,Ar Br + Ag Bg + Ab Bb)

(Cr Dr + Cg Dg + Cb Db,Cr Dr + Cg Dg + Cb Db,Cr Dr + Cg Dg + Cb Db)

(Ar Br + Cr Dr,Ag Bg + Cg Bg,Ab Bb + Cb Db)

(Ar Br mux Cr Dr,Ag Bg mux Cg Bg,Ab Bb mux Cb Db)

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NV_register_combinersGeneral Combiner Mux Computation

the AB mux CD computation is

if (texture 0 alpha > 0.5)output AB

elseoutput CD

note that texture 0 alpha is initially undefined if textureunit zero is not enabled

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NV_register_combinersGeneral Combiner Input Mapping Modes

•unsigned identity[0, 1] -> [0, 1]max(0.0, x)

•unsigned invert[0, 1] -> [1, 0]1.0 - min(max(x, 0.0, 1.0))

•expand normal[0, 1] -> [-1, 1]2.0 * max(0, x) - 1.0

•expand negate[0, 1] -> [1, -1]-2.0 * max(0.0, x) + 1.0

•half bias normal[0, 1] -> [-0.5, 0.5]max(0.0, x) - 0.5

•half bias negate[0, 1] -> [0.5, -0.5]-max(0.0, x) + 0.5

•signed identity[-1, 1] -> [-1 1]x

•signed negate[-1, 1] -> [1, -1]-x

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NV_register_combinersGeneral Combiner Scale & Bias Modes

•Scale by 1.0, no biasx

•Scale by 1.0, bias by -0.5x - 0.5

•Scale by 0.5, no bias0.5 * x


•Scale by 2.0, bias by -0.52.0 * x - 0.5


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NV_register_combinersGeneral Combiner Stage Register Outputs

six outputs per general combiner stage:

three RGB outputs (AB, CD, ABCD)written to RGB portion of writable registers

three Alpha outputs (AB, CD, ABCD)written to Alpha portion of writable registers

RGB outputs must be written to distinct registersAlpha outputs must be written to distinct registers

I.e., outputs can not be written to same register portion

if either the RGB AB or CD output of a stage computes a dot product, the RGB ABCD output for the stage must be discarded

any output can be discarded

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zero

primary color

secondary color

constant color 0

constant color 1

fog

spare 1

spare 0

texture 0

texture 1

A B + C D

A B mux C D

-or-

A B

C D

A B C D

inputmap

inputmap

inputmap

not writeable

RGB A RGB A

input registers

computations

output registers

General Combiner Operation, Alpha portion

scaleandbias

inputmap

not readableonly blue componentis readable from RGB

written output registers mustbe mutually exclusive

zero

primary color

secondary color

constant color 0

constant color 1

fog

spare 1

spare 0

texture 0

texture 1

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NV_register_combinersGeneral Combiner Stage Alpha Computations

A = (Aa) B = (Ba) C = (Ca) D = (Da)

A B C D

(Aa Ba) (Ca Da)

A B + C D A B mux C D

AB output ABCD output CD output

(Aa Ba + Ca Da) (Aa Ba mux Ca Da)

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zero

primary color

secondary color

constant color 0

constant color 1

fog

spare 1

spare 0

texture 0

texture 1

A B C D

RGB A

input registers

computations

Final Combiner Operation

A B + ( 1 - A) C + D

G

E F

E F

G

spare 0 +secondary color

inputmap

inputmap

inputmap

inputmap

inputmap

inputmap

inputmap

fragment RGB out

fragment Alpha out

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NV_register_combinersFinal Combiner Input Mapping Modes

•unsigned identity[0, 1] -> [0, 1]max(0.0, x)

•unsigned invert[0, 1] -> [1, 0]1.0 - min(max(x, 0.0, 1.0))

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NV_register_combinersFinal Combiner Color Sum Clamping

•spare 0 + secondary color clamping optionsclamp to [0,1] rangeor sum has [0, 2] range

•A B + (1-A) C + D operates in [0, 4] range

But bug in GeForce and Quadro hardware means useful range is [0, 2].

This bug is fixed in subsequent hardware!

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NV_register_combinersOpenGL API

Register Combiners Enable/Disable

Enable register combiners

glEnable(GL_REGISTER_COMBINERS_NV);

Disable register combiners

glDisable(GL_REGISTER_COMBINERS_NV);

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General Combiner Input/Output Control

glCombinerInputNV(GLenum stage,GLenum portion,GLenum variable,GLenum input,GLenum mapping,GLenum componentUsage);

glCombinerOutputNV(GLenum stage,GLenum portion,GLenum abOutput,GLenum cdOutput,GLenum sumOutput,GLenum scale,GLenum bias,GLboolean abDotProduct,GLboolean cdDotProduct,GLboolean muxSum);

Red indicates specifiersBlue indicates state values

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General Combiner Input/Output Control Tokens

stage = { GL_COMBINER0_NV, GL_COMBINER1_NV }portion = { GL_RGB, GL_ALPHA }variable = { GL_VARIABLE_A_NV, GL_VARIABLE_B_NV,

GL_VARIABLE_C_NV, GL_VARIABLE_D_NV }input = { GL_ZERO, GL_PRIMARY_COLOR_NV, GL_SECONDARY_COLOR_NV,

GL_CONSTANT_COLOR0_NV, GL_CONSTANT_COLOR1_NV,GL_TEXTURE0_ARB, GL_TEXTURE1_ARB, GL_FOG,GL_SPARE0_NV, GL_SPARE1_NV }

mapping = { GL_UNSIGNED_IDENTITY_NV, GL_UNSIGNED_INVERT_NV,GL_EXPAND_NORMAL_NV, GL_EXPAND_NEGATE_NV,GL_HALF_BIAS_NORMAL_NV, GL_HALF_BIAS_NEGATE_NV,GL_SIGNED_IDENTITY_NV, GL_SIGNED_NEGATE_NV }

componentUsage = { GL_RGB, GL_BLUE, GL_ALPHA }abOutput, cdOutput,sumOutput = { GL_DISCARD_NV,

GL_PRIMARY_COLOR_NV, GL_SECONDARY_COLOR_NV,GL_TEXTURE0_ARB, GL_TEXTURE1_ARB,GL_SPARE0_NV, GL_SPARE1_NV }

scale = { GL_NONE, GL_SCALE_BY_TWO_NV, GL_SCALE_BY_FOUR_NV,GL_SCALE_BY_ONE_HALF_NV }

bias = { GL_NONE, GL_BIAS_BY_NEGATIVE_ONE_HALF_NV }

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Final Combiner Input Control

glFinalCombinerInputNV(GLenum variable,GLenum input,GLenum mapping,GLenum componentUsage);

Red indicates specifiersBlue indicates state values

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Final Combiner Input Control Tokens

variable = { GL_VARIABLE_A_NV, GL_VARIABLE_B_NV,GL_VARIABLE_C_NV, GL_VARIABLE_D_NV,

GL_VARIABLE_E_NV, GL_VARIABLE_F_NV,GL_VARIABLE_G_NV }

input = { GL_ZERO, GL_PRIMARY_COLOR_NV, GL_SECONDARY_COLOR_NV,GL_CONSTANT_COLOR0_NV, GL_CONSTANT_COLOR1_NV,GL_TEXTURE0_ARB, GL_TEXTURE1_ARB, GL_FOG,GL_SPARE0_NV, GL_SPARE1_NV,GL_E_TIMES_F_NV, GL_SPARE0_PLUS_SECONDARY_COLOR_NV }

mapping = { GL_UNSIGNED_IDENTITY_NV, GL_UNSIGNED_INVERT_NV }componentUsage = { GL_RGB, GL_BLUE, GL_ALPHA }

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Combiner Parameter Control

glCombinerParameterfvNV(GLenum pnamev,const GLfloat *params);

glCombinerParameterivNV(GLenum pname,const GLint *params);

glCombinerParameterfNV(GLenum pname,GLfloat param);

glCombinerParameteriNV(GLenum pnamev,GLint param);

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Combiner Parameter Control Tokens

pname = { GL_NUM_COMBINERS_NV, GL_COLOR_SUM_CLAMP_NV }

pnamev = { GL_NUM_COMBINERS_NV, GL_COLOR_SUM_CLAMP_NV,GL_CONSTANT_COLOR0_NV, GL_CONSTANT_COLOR1_NV }

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Combiner State Queries

glGetCombinerInputParameterfvNV(GLenum stage,GLenum portion,GLenum variable,GLenum pname_i,GLfloat *params);

glGetCombinerInputParameterivNV(GLenum stage,GLenum portion,GLenum variable,GLenum pname_i,GLint *params);

glGetCombinerOutputParameterfvNV(GLenum stage,GLenum portion, GLenum pname_o,GLfloat *params);

glGetCombinerOutputParameterivNV(GLenum stage,GLenum portion, GLenum pname_o,GLint *params);

glGetFinalCombinerInputParameterfvNV(GLenum fvariable,GLenum pname_i,GLfloat *params);

glGetFinalCombinerInputParameterivNV(GLenum fvariable,GLenum pname_i,GLfloat *params);

Red indicates specifiers

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Combiner State Queries Tokens

stage = { GL_COMBINER0_NV, GL_COMBINER1_NV }portion = { GL_RGB, GL_ALPHA }variable = { GL_VARIABLE_A_NV, GL_VARIABLE_B_NV,

GL_VARIABLE_C_NV, GL_VARIABLE_D_NV }fvariable = { GL_VARIABLE_A_NV, GL_VARIABLE_B_NV,

GL_VARIABLE_C_NV, GL_VARIABLE_D_NV,GL_VARIABLE_E_NV, GL_VARIABLE_F_NV,GL_VARIABLE_G_NV }

pname_i = { GL_COMBINER_INPUT_NV, GL_COMBINER_MAPPING_NV,GL_COMPONENT_USAGE_NV }

pname_o = { GL_COMBINER_AB_DOT_PRODUCT_NV,GL_COMBINER_CD_DOT_PRODUCT_NV,GL_COMBINER_MUX_SUM_NV,GL_COMBINER_SCALE_NV,GL_COMBINER_BIAS_NV,GL_COMBINER_AB_OUTPUT_NV,GL_COMBINER_CD_OUTPUT_NV,GL_COMBINER_SUM_OUTPUT_NV }

geforce 256 and riva tnt combiners -...

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