1 / 46

Programmable Graphics Hardware

Programmable Graphics Hardware. Admin. Handout: Cg in two pages OLS 002a lab Impact on homework. Acknowledgement & Aside. The bulk of this lecture comes from slides from Bill Mark’s SIGGRAPH 2002 course talk on NVIDIA’s programmable graphics technology

alijah
Download Presentation

Programmable Graphics Hardware

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ProgrammableGraphics Hardware David Luebke 14/1/2014

  2. Admin • Handout: Cg in two pages • OLS 002a lab • Impact on homework David Luebke 24/1/2014

  3. Acknowledgement & Aside • The bulk of this lecture comes from slides from Bill Mark’s SIGGRAPH 2002 course talk on NVIDIA’s programmable graphics technology • For this reason, and because the lab is outfitted with GeForce 3 cards, we will focus on NVIDIA tech David Luebke 34/1/2014

  4. Outline • Programmable graphics • NVIDIA’s next-generation technology: GeForceFX (code name NV30) • Programming programmable graphics • NVIDIA’s Cg language David Luebke 44/1/2014

  5. GPU Programming Model CPU GPU VertexProcessor FragmentProcessor FramebufferOperations Assembly &Rasterization Application Framebuffer Textures David Luebke 54/1/2014

  6. 32-bit IEEE floating-pointthroughout pipeline • Framebuffer • Textures • Fragment processor • Vertex processor • Interpolants David Luebke 64/1/2014

  7. Hardware supports several other data types • Fragment processor also supports: • 16-bit “half” floating point • 12-bit fixed point • These may be faster than 32-bit on some HW • Framebuffer/textures also support: • Large variety of fixed-point formats • E.g., classical 8-bit per component • These formats use less memory bandwidth than FP32 David Luebke 74/1/2014

  8. Vertex processor capabilities • 4-vector FP32 operations, as in GeForce3/4 • True data-dependent control flow • Conditional branch instruction • Subroutine calls, up to 4 deep • Jump table (for switch statements) • Condition codes • New arithmetic instructions (e.g. COS) • User clip-plane support David Luebke 84/1/2014

  9. Vertex processor has high resource limits • 256 instructions per program(effectively much higher w/branching) • 16 temporary 4-vector registers • 256 “uniform” parameter registers • 2 address registers (4-vector) • 6 clip-distance outputs David Luebke 94/1/2014

  10. Fragment processor has clean instruction set • General and orthogonal instructions • Much better than previous generation • Same syntax as vertex processor: MUL R0, R1.xyz, R2.yxw; • Full set of arithmetic instructions:RCP, RSQ, COS, EXP, … David Luebke 104/1/2014

  11. Fragment processor hasflexible texture mapping • Texture reads are just another instruction(TEX, TXP, or TXD) • Allows computed texture coordinates,nested to arbitrary depth • Allows multiple uses of a singletexture unit • Optional LOD control – specify filter extent • Think of it as…A memory-read instruction,with optional user-controlled filtering David Luebke 114/1/2014

  12. Additional fragment processor capabilities • Read access to window-space position • Read/write access to fragment Z • Built-in derivative instructions • Partial derivatives w.r.t. screen-space x or y • Useful for anti-aliasing • Conditional fragment-kill instruction • FP32, FP16, and fixed-point data David Luebke 124/1/2014

  13. Fragment processor limitations • No branching • But, can do a lot with condition codes • No indexed reads from registers • Use texture reads instead • No memory writes David Luebke 134/1/2014

  14. Fragment processor has high resource limits • 1024 instructions • 512 constants or uniform parameters • Each constant counts as one instruction • 16 texture units • Reuse as many times as desired • 8 FP32 x 4 perspective-correct inputs • 128-bit framebuffer “color” output(use as 4 x FP32, 8 x FP16, etc…) David Luebke 144/1/2014

  15. NV30 CineFX Technology Summary VertexProcessor FragmentProcessor FramebufferOperations Assembly &Rasterization Application Framebuffer Textures • FP32 throughout pipeline • Clean instruction sets • True branching in vertex processor • Dependent texture in fragment processor • High resource limits David Luebke 154/1/2014

  16. Programming in assembly is painful Assembly …FRC R2.y, C11.w; ADD R3.x, C11.w, -R2.y; MOV H4.y, R2.y; ADD H4.x, -H4.y, C4.w; MUL R3.xy, R3.xyww, C11.xyww; ADD R3.xy, R3.xyww, C11.z; TEX H5, R3, TEX2, 2D; ADD R3.x, R3.x, C11.x; TEX H6, R3, TEX2, 2D;… … L2weight = timeval – floor(timeval); L1weight = 1.0 – L2weight; ocoord1 = floor(timeval)/64.0 + 1.0/128.0; ocoord2 = ocoord1 + 1.0/64.0; L1offset = f2tex2D(tex2, float2(ocoord1, 1.0/128.0)); L2offset = f2tex2D(tex2, float2(ocoord2, 1.0/128.0)); … • Easier to read and modify • Cross-platform • Combine pieces • etc. David Luebke 164/1/2014

  17. Quick Demo David Luebke 174/1/2014

  18. Cg – C for Graphics • Cg is a GPU programming language • Designed by NVIDIA and Microsoft • Compilers available in beta versions from both companies David Luebke 184/1/2014

  19. Design goals for Cg • Enable algorithms to be expressed… • Clearly, and • Efficiently • Provide interface continuity • Focus on DX9-generation HW and beyond • But provide support for DX8-class HW too • Support both OpenGL and Direct3D • Allow easy, incremental adoption David Luebke 194/1/2014

  20. Easy adoption for applications • Avoid owning the application’s data • No scene graph • No buffering of vertex data • Compiler sits on top of existing APIs • User can examine assembly-code output • Can compile either at run time, or at application-development time • Allow partial adoption e.g. Use Cg vertex program with assembly fragment program • Support current hardware David Luebke 204/1/2014

  21. Some points inthe design space • CPU languages • C – close to the hardware; general purpose • C++, Java, lisp – require memory management • RenderMan – specialized for shading • Real-time shading languages • Stanford shading language • Creative Labs shading language David Luebke 214/1/2014

  22. Design strategy • Start with C(and a bit of C++) • Minimizes number of decisions • Gives you known mistakes instead of unknown ones • Allow subsetting of the language • Add features desired for GPU’s • To support GPU programming model • To enable high performance • Tweak to make it fit together well David Luebke 224/1/2014

  23. How are current GPU’s different from CPU? • GPU is a stream processor • Multiple programmable processing units • Connected by data flows VertexProcessor FragmentProcessor FramebufferOperations Assembly &Rasterization Application Framebuffer Textures David Luebke 234/1/2014

  24. Cg uses separate vertexand fragment programs VertexProcessor FragmentProcessor FramebufferOperations Assembly &Rasterization Application Framebuffer Textures Program Program David Luebke 244/1/2014

  25. Cg programs have twokinds of inputs • Varying inputs (streaming data) • e.g. normal vector – comes with each vertex • This is the default kind of input • Uniform inputs (a.k.a. graphics state) • e.g. modelview matrix • Note: Outputs are always varying vout MyVertexProgram(float4 normal, uniform float4x4 modelview) { … David Luebke 254/1/2014

  26. Two ways to bind VP outputs to FP inputs • Let compiler do it • Define a single structure • Use it for vertex-program output • Use it for fragment-program input struct vout { float4 color; float4 texcoord; … }; David Luebke 264/1/2014

  27. Two ways to bind VP outputs to FP inputs • Do it yourself • Specify register bindings for VP outputs • Specify register bindings for FP inputs • May introduce HW dependence • Necessary for mixing Cg with assembly struct vout { float4 color : TEX3 ; float4 texcoord : TEX5; … }; David Luebke 274/1/2014

  28. Some inputs and outputs are special • e.g. the position output from vert prog • This output drives the rasterizer • It must be marked struct vout { float4 color; float4 texcoord; float4 position : HPOS; }; David Luebke 284/1/2014

  29. How are current GPU’s different from CPU? • Greater variation in basic capabilities • Most processors don’t yet support branching • Vertex processors don’t support texture mapping • Some processors support additional data types • Compiler can’t hide these differences • Least-common-denominator is too restrictive • We expose differences via language profiles(list of capabilities and data types) • Over time, profiles will converge David Luebke 294/1/2014

  30. How are current GPU’s different from CPU? • Optimized for 4-vector arithmetic • Useful for graphics – colors, vectors, texcoords • Easy way to get high performance/cost • C philosophy says: expose these HW data types • Cg has vector data types and operationse.g. float2, float3, float4 • Makes it obvious how to get high performance • Cg also has matrix data typese.g. float3x3, float3x4, float4x4 David Luebke 304/1/2014

  31. Some vector operations // // Clamp components of 3-vector to [minval,maxval] range // float3 clamp(float3 a, float minval, float maxval) { a = (a < minval.xxx) ? minval.xxx : a; a = (a > maxval.xxx) ? maxval.xxx : a; return a; } ? : is per-component for vectors Swizzle – replicate and/or rearrange components. Comparisons between vectorsare per-component, andproduce vector result David Luebke 314/1/2014

  32. Cg has arrays too • Declared just as in C • But, arrays are distinct frombuilt-in vector types:float4 != float[4] • Language profiles may restrict array usage vout MyVertexProgram(float3 lightcolor[10], …) { … David Luebke 324/1/2014

  33. How are current GPU’s different from CPU? • No support for pointers • Arrays are first-class data types in Cg • No integer data type • Cg adds “bool” data type for boolean operations • This change isn’t obvious except when declaring vars David Luebke 334/1/2014

  34. Cg basic data types • All profiles: • float • bool • All profiles with texture lookups: • sampler1D, sampler2D, sampler3D,samplerCUBE • NV_fragment_program profile: • half -- half-precision float • fixed -- fixed point [-2,2) David Luebke 344/1/2014

  35. Other Cg capabilities • Function overloading • Function parameters are value/result • Use “out” modifier to declare return value • “discard” statement – fragment kill void foo (float a, out float b) { b = a; } if (a > b) discard; David Luebke 354/1/2014

  36. Cg Built-in functions • Texture mapping (in fragment profiles) • Math • Dot product • Matrix multiply • Sin/cos/etc. • Normalize • Misc • Partial derivative (when supported) • See spec for more details David Luebke 364/1/2014

  37. New vector operators • Swizzle – replicate/rearrange elements a = b.xxyy; • Write mask – selectively over-write a.w = 1.0; • Vector constructor builds vectora = float4(1.0, 0.0, 0.0, 1.0); David Luebke 374/1/2014

  38. Change to constant-typing mechanism • In C, it’s easy to accidentally use high precision half x, y; x = y * 2.0; // Double-precision multiply! • Not in Cg x = y * 2.0; // Half-precision multiply • Unless you want to x = y * 2.0f; // Float-precision multiply David Luebke 384/1/2014

  39. Dot product,Matrix multiply • Dot product • dot(v1,v2); // returns a scalar • Matrix multiplications: • matrix-vector: mul(M, v); // returns a vector • vector-matrix: mul(v, M); // returns a vector • matrix-matrix: mul(M, N); // returns a matrix David Luebke 394/1/2014

  40. Demos and Examples • Show Assn 4a skeleton code • Show Cg effects browser ( • Fresnel • Simple lighting David Luebke 404/1/2014

  41. Cg runtime API helpsapplications use Cg • Compile a program • Select active programs for rendering • Pass “uniform” parameters to program • Pass “varying” (per-vertex) parameters • Load vertex-program constants • Other housekeeping David Luebke 414/1/2014

  42. Runtime is split into three libraries • API-independent layer – cg.lib • Compilation • Query information about object code • API-dependent layer –cgGL.lib and cgD3D.lib • Bind to compiled program • Specify parameter values • etc. • NB: New API introduced since the following slide • See user’s manual for details • Pay attention to the basic idea here David Luebke 424/1/2014

  43. Runtime API for OpenGL // Create cgContext to hold vertex-profile code VertexContext = cgCreateContext(); // Add vertex-program source text to vertex-profile context // This is where compilation currently occurs cgAddProgram(VertexContext, CGVertProg, cgVertexProfile, NULL); // Get handle to 'main' vertex program VertexProgramIter = cgProgramByName(VertexContext, "main"); cgGLLoadProgram(VertexProgramIter, ProgId); VertKdBind = cgGetBindByName(VertexProgramIter, "Kd"); TestColorBind = cgGetBindByName(VertexProgramIter, "I.TestColor"); texcoordBind = cgGetBindByName(VertexProgramIter, "I.texcoord"); David Luebke 434/1/2014

  44. Runtime API for OpenGL // // Bind uniform parameters // cgGLBindUniform4f(VertexProgramIter, VertKdBind, 1.0, 1.0, 0.0, 1.0); … // Prepare to render cgGLEnableProgramType(cgVertexProfile); cgGLEnableProgramType(cgFragmentProfile); … // Immediate-mode vertex glNormal3fv(&CubeNormals[i][0]); cgGLBindVarying2f(VertexProgramIter, texcoordBind, 0.0, 0.0); cgGLBindVarying3f(VertexProgramIter, TestColorBind, 1.0, 0.0, 0.0); glVertex3fv(&CubeVertices[CubeFaces[i][0]][0]); David Luebke 444/1/2014

  45. Cg Summary • C-like language • With capabilities for GPU’s • Compatible with Microsoft’s HLSL • Use with OpenGL or DirectX • NV20/DX8 and beyond • NV30 + Cg =You control the graphics pipeline David Luebke 454/1/2014

  46. More Information • The Cg Tutorial book • NVIDIA’s “Learn About Cg” page: • http://developer.nvidia.com/view.asp?IO=cg_about • For information, inspiration, and examples, a web forum on writing Cg shaders: • http://www.shadertech.com/ • The Cg user’s manual: • ftp://download.nvidia.com/developer/cg/Cg_1.2.1/Docs/Cg_Toolkit.pdf • Cg downloads—compiler, plug-ins, etc. • http://developer.nvidia.com/object/cg_toolkit.html David Luebke 464/1/2014

More Related