Modern Graphics Hardware 2002 Vertex Programs

1. Modern Graphics Hardware2002Vertex Programs Joe Michael Kniss

2. Overview • Pipeline overview • VP/FP overview • Vertex Programs – Me • Fragment Programs – Aaron • Discussion

3. Primitive construction Tessellation Transform to homogeneous eye space, light, texgen, deform… Transform & Lighting Triangle setup View volume clip, view surface coordinates Generate fragments, interpolate color & texcoords Rasterization Fragment processing Access textures, & compute final color Stencil, alpha, scissor, depth …. Tests Add, mult, interpolate, max… Blending Anti-Aliasing Modern Graphics Hardware

4. 03? Primitive construction Primitive Programs? Fragment Programs Transform & Lighting Vertex Programs 00 02 01 99 Triangle setup Rasterization Pre--98 Vertex Programs Fragment Programs Vertex Programs 2.0 Fragment processing Tests Combiners Blending Anti-Aliasing Modern Graphics Hardware

5. Higher order surface Transform & Lighting Vertex Programs Fragment Programs Triangle setup Rasterization Fragment processing Tests Blending Anti-Aliasing Higher order surfaces • PN Triangles (ATI) • Bezier patches (NVIDIA)

6. Higher order surface Transform & Lighting Fragment Programs Vertex Programs Triangle setup Rasterization Fragment processing Tests Blending Anti-Aliasing Vertex Programs 16 input vectors 256 static vectors 12 temp vectors Loops 22 output vectors Post T&L cache

7. 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

8. Vertex Programs • First generation (nv1.0, ati ext, ARB1.0) • 128 instructions • 96 constants • 12 temps • No loops 16 input vectors 96 static vectors 12 temp vectors 15 output vectors Post T&L cache

9. 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, ...)

10. 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)

11. Vertex Programs 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 • First gen instruction set

12. 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

13. 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??)

14. 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

15. 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!!!

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

17. 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!

18. 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; …

19. 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; }

20. 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 input vectors 256 static vectors 12 temp vectors Loops 22 output vectors Post T&L cache

21. 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)

22. 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

23. Questions? … now on to Fragment Programs