Modern Graphics Hardware2002

Vertex ProgramsJoe Michael Kniss

Overview

• Pipeline overview

• VP/FP overview

• Vertex Programs – Me

• Fragment Programs – Aaron

• Discussion

Modern Graphics Hardware

Anti-Aliasing

Primitive construction Tessellation

Transform & Lighting

Transform to homogeneous eye space, light, texgen, deform…

Triangle setup View volume clip, view surface coordinates

Rasterization Generate fragments, interpolate color & texcoords

Fragment processing

Access textures, & compute final color

Tests Stencil, alpha, scissor, depth ….

Blending Add, mult, interpolate, max…

Modern Graphics Hardware

Primitive construction

Transform & Lighting

Triangle setup

Rasterization

Fragment processing

Tests

Blending Anti-Aliasing

Pre--98

99

00 Vertex Programs 01

CombinersFragment Programs

Vertex Programs 2.0 02

Primitive Programs?

03?

Vertex Programs

Fragment Programs

Higher order surfaces

Higher order surface

Transform & Lighting

Triangle setup

Rasterization

Fragment processing

Tests

Blending Anti-Aliasing

Vertex Programs

Fragment Programs

• PN Triangles (ATI)

•Bezier patches (NVIDIA)

Vertex Programs

Higher order surface

Transform & Lighting

Triangle setup

Rasterization

Fragment processing

Tests

Blending Anti-Aliasing

Vertex Programs

Fragment Programs

16 inputvectors

256 staticvectors 12 temp

vectors

22 outputvectors

Post T&L cache

Loops

Vertex Programs

• 3-5 flavors– nv vertex programs 1.0 & 2.0– ati vertex program (EXT)– ARB vertex program 1.0 ( & 2.0 ???)

• nv 1.0 + ati ext ARB 1.0

• Next gen == ARB 2.0 ????

• Closely matches Direct3D

Vertex Programs

• First generation (nv1.0, ati ext, ARB1.0)– 128 instructions– 96 constants– 12 temps– No loops

16 inputvectors

96 staticvectors 12 temp

vectors

15 outputvectors

Post T&L cache

Vertex Programs

• First gen. inputs

Generic Attribute Conventional Attribute Conventional Attribute Command --------- ------------------------ ------------------------------ 0 vertex position Vertex 1 vertex weights 0-3 WeightARB, VertexWeightEXT 2 normal Normal 3 primary color Color 4 secondary color SecondaryColorEXT 5 fog coordinate FogCoordEXT 6 - - 7 - - 8 texture coordinate set 0 MultiTexCoord(TEXTURE0, ...) 9 texture coordinate set 1 MultiTexCoord(TEXTURE1, ...) 10 texture coordinate set 2 MultiTexCoord(TEXTURE2, ...) 11 texture coordinate set 3 MultiTexCoord(TEXTURE3, ...) 12 texture coordinate set 4 MultiTexCoord(TEXTURE4, ...) 13 texture coordinate set 5 MultiTexCoord(TEXTURE5, ...) 14 texture coordinate set 6 MultiTexCoord(TEXTURE6, ...) 15 texture coordinate set 7 MultiTexCoord(TEXTURE7, ...) 8+n texture coordinate set n MultiTexCoord(TEXTURE0+n, ...)

Vertex Programs

• First gen. inputs Conventional Attribute Binding Generic Attribute Binding ------------------------------ ------------------------- vertex.position vertex.attrib[0] vertex.weight vertex.attrib[1] vertex.weight[0] vertex.attrib[1] vertex.normal vertex.attrib[2] vertex.color vertex.attrib[3] vertex.color.primary vertex.attrib[3] vertex.color.secondary vertex.attrib[4] vertex.fogcoord vertex.attrib[5] vertex.texcoord vertex.attrib[8] vertex.texcoord[0] vertex.attrib[8] vertex.texcoord[1] vertex.attrib[9] vertex.texcoord[2] vertex.attrib[10] vertex.texcoord[3] vertex.attrib[11] vertex.texcoord[4] vertex.attrib[12] vertex.texcoord[5] vertex.attrib[13] vertex.texcoord[6] vertex.attrib[14] vertex.texcoord[7] vertex.attrib[15] vertex.texcoord[n] vertex.attrib[8+n]

ARB 1.0 notation (inputs == Read only)

Vertex Programs

• First gen instruction set Instruction Inputs Output Description ----------- ------ ------ -------------------------------- ABS v v absolute value ADD v,v v add ARL v a address register load DP3 v,v ssss 3-component dot product DP4 v,v ssss 4-component dot product DPH v,v ssss homogeneous dot product DST v,v v distance vector EX2 s ssss exponential base 2 EXP s v exponential base 2 (approximate) FLR v v floor FRC v v fraction LG2 s ssss logarithm base 2 LIT v v compute light coefficients LOG s v logarithm base 2 (approximate) MAD v,v,v v multiply and add MAX v,v v maximum MIN v,v v minimum MOV v v move MUL v,v v multiply POW s,s ssss exponentiate RCP s ssss reciprocal RSQ s ssss reciprocal square root SGE v,v v set on greater than or equal SLT v,v v set on less than SUB v,v v subtract SWZ v v extended swizzle XPD v,v v cross product

Vertex Programs

• First gen instruction set– Wow! That’s a lot of instructions– Why: SIMD processor– Single clock execution– Taken from ARB spec, not all instructions

available on all platforms

Vertex Programs

• First gen. outputs

Binding Components Description ----------------------------- ---------- ---------------------------- result.position (x,y,z,w) position in clip coordinates result.color (r,g,b,a) front-facing primary color result.color.primary (r,g,b,a) front-facing primary color result.color.secondary (r,g,b,a) front-facing secondary color result.color.front (r,g,b,a) front-facing primary color result.color.front.primary (r,g,b,a) front-facing primary color result.color.front.secondary (r,g,b,a) front-facing secondary color result.color.back (r,g,b,a) back-facing primary color result.color.back.primary (r,g,b,a) back-facing primary color result.color.back.secondary (r,g,b,a) back-facing secondary color result.fogcoord (f,*,*,*) fog coordinate result.pointsize (s,*,*,*) point size result.texcoord (s,t,r,q) texture coordinate, unit 0 result.texcoord[n] (s,t,r,q) texture coordinate, unit n

ARB 1.0 notation (outputs == Write only??)

Vertex Programs

• What’s special about the ARB 1.0 spec?– Unifies coding for multiple platforms

(That’s their job!)– Access to “tracked” OGL state

(Materials, Matrices,…)– Unifies vertex programs and next gen

fragment programs

Vertex Programs

• ARB 1.0 continued– Position invariant vertex programs

• Use the fixed function pipe to transform vertices• You still do the lighting• Same transformation even if vertex program

enabled• Option set in VP text file• KEY for multi-pass algorithms!!!

Vertex Programs

• ARB 1.0 continued…– Vender specific “enhancements”– Access special functionality of chip– Use “OPTION BLAH” at top of program text

Vertex Programs

• Other ARB 1.0 features– Constant scoping, env, state, local

• Determines life time & update behavior

– Temporary aliasing (tmp1 = tmp2)– Automatic constant management, let

driver deal with constant numbering!

Vertex Programs

• ARB 1.0 example

!!ARBvp1.0

# comment here ;)

ATTRIB pos = vertex.position; #alias long names

ATTRIB norm = vertex.normal;

PARAM mv[4] = { state.matrix.modelview }; #alias

PARAM mvit[4] = { state.matrix.modelview.invtrans };

TEMP tnorm; # temp for the transformed normal

DP4 result.position.x mv[0] pos; # vertex to clip space

DP4 result.position.y mv[1] pos;

DP4 result.position.z mv[2] pos;

DP4 result.position.w mv[3] pos;

DP3 tnorm.x mvit[0] norm; # tranform the normal

DP3 tnorm.y mvit[1] norm; # for lighting (later)

DP3 tnorm.z mvit[2] norm;

…

Vertex Programs

• Same example in Cg:struct appin : application2vertex{

float4 pos : POSITION;float4 Norm : NORMAL;

};struct vertout : vertex2fragment{

float4 HPos : POSITION;float4 PCol : COLOR0;

};

vertout main(appin IN){ vertout out; out.Hpos = mul(glstate.matrix.mvp, IN.pos); // note cast to float3 for the normal!!!! float3 tnorm = mul(glstate.matrix.invtrans.modelview[0],(float3)IN.norm); … return out;}

Vertex Programs

• Next generation (nv2.0, ati ?, ARB2.0?)– 256 instructions– 256 constants– 12 temps ?– Loops– Subroutines– Conditional branching– 4 address registers– 6 clips & 8 textures

16 inputvectors

256 staticvectors 12 temp

vectors

22 outputvectors

Post T&L cache

Loops

Vertex Programs

• Next gen vertex programs– True conditional branching, looping and

subroutine calls– Conditional write masks– Enhanced instruction set

(frac, floor, sin, cos, ex2, lg2, pow, lerp)

– More everything vs. NV2X• instructions (from 128 to 256)• constants (from 96 to 256)• address registers (from 1 to 4)• texture coordinate sets (from 4 to 8)• clip planes (from 0 to 6)

Vertex Programs

• ARB vp2.0 not ratified yet– Have to use vendor specifics till then– Who knows when???– Still follows Direct3D, no problem??– Need uniformity for programmers sake

Questions?

… now on to Fragment Programs