IN4151 Introduction 3D graphics 1 Introduction to 3D computer graphics part 2 Viewing pipeline Multi-processor implementation GPU architecture GPU algorithms

IN4151 Introduction 3D graphics 2 Viewing pipeline model from database approximate curved surfaces by polygons viewing transformation light intensityclipping perspective divide window to viewport transformation edge processing span interpolation texture mapping depth buffer test area summing r,g,b, z, a-buf CPU geometry processing fragment/ pixel processing 500 Mflops 5000 Mips 100 Mpix/s 1 M polygons/s scan-conversion

IN4151 Introduction 3D graphics 3 Load balancing and bottlenecks FB M D/A Pipeline is good for geometric processing (#vertices) Viewing transformations Shading Clipping Perspective projection Viewport transformations Access to frame buffer is now bottleneck Span interpolation Depth testing Texture mapping Alpha blending Farm is better for scanline and pixel processing (#pixels) H P P P P P P P P FIF O buffer

IN4151 Introduction 3D graphics 4 Distributed frame buffers Distribution for R,G,B and Z Distribution by image subdivision FB D/A M P P H P P FB-R FB-G FB-B FB-Z H P P P P D/A M PPP PPP PPP PPP P P P P H P P P P

IN4151 Introduction 3D graphics 5 Segmented –Coherence –No load balancing Interlaced –Scan-line coherence –Better load balancing Interleaved –No coherence –Optimal balance Frame buffer distributions : 1,2,3,4,17,18,.. 2 : 5,6,7,8,21,22,.. 3 : 9,10,11,12,25,.. 4 : 13,14,15,16,29,.. 5 : 65,66,... 6 :.. 1 : 1,2,3,4,5,6,... 17,18,19, : 33,34,35, : 1,5,9,13, 65,... 2 : 2,6,10,14,... 3 : 3,7,11,15,... 4 : 4,8,12,16,... 5 : 17,21,25,29,... 6 : 18,22,26,... 7 :

IN4151 Introduction 3D graphics 6 Render architecture interleaved frame buffer Silicon Graphics IRIS polygons/s GA GE PP x y z r g b a SP VP IE geometry subsystem scan conversion subsystem raster subsystem display subsystem polygon processor image engines +VRAM video processors geometric engines processors screen geometric accelerator edge processors span processors Access to texture memory is bottleneck...

IN4151 Introduction 3D graphics 7 PC-graphics card Game industry 4-16 processors parallel SIMD machine Larger texture memory Multiple passes Programmable GPU: vertex and fragment/pixel shaders texture memory frame buffer vertex operations transform, lighting rasterization color, texture interpolation pixel operations depth compare, alpha test, blending, filtering polygon memory

IN4151 Introduction 3D graphics 8 GPU processing / programming Bump mapping, shadow map, environment map BRDF shading, image based rendering Image processing, filtering, segmentation Use texture memory as internal memory Map functions to tables Some limitations: source cannot be sink Limited number of indirections Getting data back from the graphics card is slow

IN4151 Introduction 3D graphics 9 Bump mapping Pertubate normal as a function of bump map

IN4151 Introduction 3D graphics 10 Shadows Alternative: shadow volumes image shadow map light source

IN4151 Introduction 3D graphics 11 Environment mapping Environment map represents incoming radiance for center point Can be stored in spherical map or cube Reflection is look-up in map Approximation to ray tracing!

IN4151 Introduction 3D graphics 12 Diffuse environment shading received radiance is function of accessability specular reflection diffuse reflection Need integration over environment map For diffuse reflection scaled by cosinus Index in filtered versions of map ambient occlusion

IN4151 Introduction 3D graphics 13 Conclusions Viewing pipeline for polygon rendering is still alive but real-time ray tracing is approaching GPU programming is powerful tool: volume rendering, physically-based modeling, dynamics, etc.