Modern Graphics Hardware 2002 Vertex Programs Joe Michael Kniss

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

Modern Graphics Hardware Anti-AliasingPrimitive 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 setupRasterizationFragment processing TestsBlendingAnti-Aliasing Pre Vertex Programs 01 Combiners Fragment Programs Vertex Programs Primitive Programs? 03? Vertex Programs Fragment Programs

Higher order surfaces Higher order surface Transform & Lighting Triangle setupRasterizationFragment processing TestsBlendingAnti-AliasingVertex Programs Fragment Programs PN Triangles (ATI) Bezier patches (NVIDIA)

Vertex Programs Higher order surface Transform & Lighting Triangle setupRasterizationFragment processing TestsBlendingAnti-AliasingVertex Programs Fragment Programs 16 input vectors 256 static vectors 12 temp vectors 22 output vectors 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 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 input vectors 96 static vectors 12 temp vectors 15 output vectors Post T&L cache

Vertex Programs First gen. inputs Generic Attribute Conventional Attribute Conventional Attribute Command 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 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 input vectors 256 static vectors 12 temp vectors 22 output vectors 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