ARB Fragment Program in GPULib

1. ARB Fragment Program in GPULib

2. Summary • Fragment program arquitecture • New instructions. • Emulating instructions not supported directly • New Required GL State • Compiler status

3. Fragment program architecture • What fragment programs bypass: • Replaces multitexturing pipe: • Replaces this calculations: • Texture blending • Color sum • Fog • What not (is preserved): • Coverage application • Alpha Test • Stencil and depth test • Blending

4. setup rasterizer User-defined Fragment Processing Texture Fetch and Application Color Sum Fog frame-buffer ops Fragment program architecture (II)

5. Program Environment Parameters Program Local Parameters Fragment program architecture (III) Attributes Fragment Program Temporary Variables Address Variables Result Registers

6. Fragment program architecture(IV) • Input attributes (called fragment attributes): • color (primary and secondary) • vector of texture coordinates (for multitexturing) • fog coordinate • position (window position + z) • Output attributes: • 2 attributes to write: • color (r,g,b,a) • depth (*,*,d,*)

7. Fragment program architecture(V) • Program local and environment parameters: • Like vertex programs: • local: private for each fragment program • env: shared for all programs (including vertex programs). • Limits (the implementation has to guarantee equal or higher limits): • Total Number of instructions: 72 • ALU instructions: 48 • Texture instructions: 24 • Texture indirections: 4 • Temporaries: 16 • Program parameters: 24

8. New instructions • The same instructions as vertex programs: • Except: • ARL: Now, no address registers to load • LOG, EXP: Remain LG2 and EX2 instructions. • Plus: • SIN, COS, SCS(leave sinus on .x and cosinus on .y) • LRP (Linear Interpolation instruction) • CMP (Compare instruction) • Note about ALU instructions: • Implementations may be able to perform fragment program computations at more than one precision: • New program option directives: • OPTION ARB_precision_hint_fastest; # Minimize execution time • OPTION ARB_precision_hint_nicest; # Maximize execution time

9. New instructions (II) • And... the Texture instructions: • Gets texture coordinates of fragment and samples the texture color corresponding to the fragment. TEX myTexel, fragment.texcoord[1], texture[2], 3D; • Extended texture fetches: • TXP and TXB

10. Texture indirections • A texture dependency occurs when a texture instruction depends on the result of a previous instruction (ALU or texture) for use as its texture coordinate. • A fragment program with no dependencies has 1 texture indirections: !!ARBfp1.0 # No texture instructions, but always 1 indirection MOV result.color, fragment.color; END • Texture dependencies sums indirection !!ARBfp1.0 # A simple dependent texture instruction, 2 indirections TEMP myColor; MUL myColor, fragment.texcoord[0], fragment.texcoord[1]; TEX result.color, myColor, texture[0], 2D; END

11. New instructions (III) • KIL instruction: KIL vectorSrcReg; • Prevents a fragment from receiving any future processing if any component of its source vector is negative • ARB instruction takes a vector operand rather than a condition code (NVIDIA) • Saturation Flag: • Optional clamping of each component of the destination register to the range [0,1] is controlled by an opcode modifier. • There is a clamped version of each instruction: ADD_SAT, TEX_SAT, CMP_SAT, LRP_SAT.

12. Instruction emulation • SIN, COS, TEX, TXP, TXB supported directly by GPU. • SCS: • Emulated using the separate SIN and COS • LRP: LPR result, op0, op1, op2; ADD result, op0, -op2; MAD result, result, op1, op2;

13. Instruction emulation • CMP: CMP dst, src0, src1, src2; SLT tmp, src0, {0,0,0,0}; LRP dst, tmp, src1, src2;

14. New GLState • GLState shared with vertex programs: • Material Properties: material ambient, diffuse, specular (for front and back faces) • Light and Lightmodel Properties: ambient, diffuse, specular, attenuation, spot direction, spot cut-off (for each GL_LIGHTX). • Matrix Properties: Modelview, MVP, projection matrices with .transpose, .inverse, .invtrans modifiers. • New GLState: • Texture Environment Color Property: • state.texenv[n].color ( n = 0 to #texture units) • Fog Properties: • RGB fog color • Params (fog density, linear start and end, and 1/(end-start)) • Depth Properties: • Depth range near, far, and (far-near)

15. Line:By0By1By2By3By4By5By6By7By8By9ByAByBByByDByEByF 011: 16 00 03 28 00 01 00 08 26 1b 6a 00 0f 1b 04 78 012: 09 00 03 00 00 00 02 08 24 1b 1b 00 08 1b 14 18 013: 09 00 04 00 00 00 02 08 24 1b 1b 00 04 1b 14 b8 014: 09 00 05 00 00 00 02 08 24 1b 1b 00 02 1b 04 58 015: 09 00 06 00 00 00 02 08 24 1b 1b 00 01 1b 04 f8 016: 16 00 01 00 00 00 02 30 24 1b 1b 00 08 1b 14 98 017: 16 00 02 00 00 01 02 30 24 1b 1b 00 08 1b 04 38 018: 16 00 00 00 00 00 03 30 24 00 1b 00 02 1b 04 d8 019: 16 00 01 00 00 00 03 30 24 00 1b 00 01 1b 14 78 020: 01 00 08 00 00 08 18 08 24 04 ae 00 0c 1b 04 18 021: 17 00 00 00 00 00 13 30 24 00 00 00 08 1b 04 b8 022: 17 00 01 00 00 00 13 30 24 00 00 00 04 1b 14 58 023: 01 00 08 00 00 09 18 08 24 04 04 00 0c 1b 14 f8 024: 01 00 08 00 00 0a 18 08 26 04 ae 00 0c 1b 04 98 025: 01 00 08 00 00 0b 18 08 26 04 04 00 0c 1b 14 38 !!ARBfp1.0 # Simple program to show how to code up # the default texture environment ATTRIB tex = fragment.texcoord; #first set of texture # coordinates ATTRIB col = fragment.color.primary; OUTPUT outColor = result.color; TEMP tmp; TXP tmp, tex, texture, 2D; #sample the texture MUL outColor, tmp, col; #perform the modulation END Code Generation Específico GPU Generic + TEX,CMP,... Current work: IR !!ARBvp1.0 Flex + Bison (Completed) (Completed) Compiler Status

16. Compiler Status • Lexical and Syntactical: Complete • Translation of generic to GPU instructions: Complete • Current Work: • Generating new IR for the fragment program grammar. • Semantic Parse and Code generation parse