大三05计算机图形学rendering

1、Parallel Rendering1Angel: Interactive Computer Graphics 5E Addison-Wesley 2009原著Ed AngelProfessor of Computer Science, Electrical and Computer Engineering, and Media ArtsUniversity of New Mexico编辑 武汉大学计算机学院图形学课程组2Angel: Interactive Computer Graphics 5E Addison-Wesley 2009IntroductionIn many situatio

2、ns, a standard rendering pipeline might not be sufficientNeed higher resolution displayMore primitives than one pipeline can handleWant to use commodity components to build a system that can render in parallelUse standard network to connect3Angel: Interactive Computer Graphics 5E Addison-Wesley 2009

3、Power WallsWhere do we display large data sets?CRTs have low resolution (1 Mpixel)LCD panels improving but still expensiveNeed resolution comparable to data set to see detailCT/MRI/MEGOcean dataSolution?Multiple projectorsCommodity High-endSee IEECE CG & A (July)4Angel: Interactive Computer Graphics

4、 5E Addison-Wesley 2009Tiled Display5Angel: Interactive Computer Graphics 5E Addison-Wesley 2009CS Power Wall6 dual processor IntellestationsG Force 3 Graphics cards6 commodity projectors (1024 x 768)Gigabit ethernetBack projected screenShared facility with scalable system groupInvestigate OS and ne

5、twork issues6Angel: Interactive Computer Graphics 5E Addison-Wesley 2009CS Power Wall7Angel: Interactive Computer Graphics 5E Addison-Wesley 2009CS Power Wall8Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Power WallInexpensive solution but there are some problemsColor matchingVignetting

6、Alignment Overlap areasSynchingDark field9Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Graphics ArchitecturesPipeline ArchitectureSGI Geometry EngineGeometry passes through pipelineHardware forclipping transformationstexture mappingProject/SortClipTransformRasterizeScreen10Angel: Inter

7、active Computer Graphics 5E Addison-Wesley 2009Building BlocksGraphics processors consist of geometric blocks and rasterizersGeometric units: transformations, clipping, lightingRasterization: scan conversion, shadingParallelize by using mutiple blocksWhere to do depth check?RGGGRR11Angel: Interactiv

8、e Computer Graphics 5E Addison-Wesley 2009Sorting ParadigmWe can categorize different ways of interconnecting blocks using a sorting paradigm: each projector is responsible for one area of the screen. Hence, we must sort the primitives and assign them to the proper projectorAlgorithms can be categor

9、ized by where this sorting occurs12Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Three Rendering MethodsSort-First RenderingSort-Middle RenderingSort-Last RenderingRGGGRRSortGGGRRRSortRGGGRRComposite13Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort FirstEach rasterizatio

10、n unit assigned to an area of the screenEach geometric unit coupled to its own rasterizerMust sort primitives firstCan use commodity cardsRGGGRRSort14Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort-First Rendering for a Random Triangles Application15Angel: Interactive Computer Graphi

11、cs 5E Addison-Wesley 2009Sort MiddleGeometric units and rasterization units decoupledEach geometric unit can be assigned any group of objectsEach rasterizer is assigned to an area of the screenMust sort between stagesGGGRRRSort16Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort LastCou

12、ple rasterizers and geometric unitsAssign objects to geometric units to load balance or via applicationComposite results at endRGGGRRComposite17Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Tree CompositingComposite in pairsSend color and depth buffersEach time half processors e idle18A

13、ngel: Interactive Computer Graphics 5E Addison-Wesley 2009Binary Swap CompositingEach processor responsible for one part of displayPass data to right n times19Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort-Last Rendering for a Random Triangles Application20Angel: Interactive Compute

14、r Graphics 5E Addison-Wesley 2009ComparisonSort firstAppealing but hard to implement Sort middleUsed in hardware pipelinesMore difficult to implement with add-on commodity cardsSort lastEasy to implement with a compositing stageHigh network traffic21Angel: Interactive Computer Graphics 5E Addison-We

15、sley 2009Mapping to ClustersDifferent architecturesShared vs distributed memoryCommunication overheadParallel vs distributed algorithmsEasy to do sort lastMust evaluate communication costStandard visualization strategies are incorrect if transparency used22Angel: Interactive Computer Graphics 5E Add

16、ison-Wesley 2009Vista AzulExperimental architecture from IBM donated to AHPCCHalf Intel nodes, half AIX nodesOnly one (PCI) graphics card per four processorsContained a Scalable Graphics Engine (SGE): high speed-high resolution color buffer that is accessible by all processors23Angel: Interactive Co

17、mputer Graphics 5E Addison-Wesley 2009Vista Azul24Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Comparison Between Sort-First and Sort-Last25Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Performance on a PC ClusterFollowing experiments were done by Ye Cong on the CS cluster

18、6 IntellestationsGigabit EthernetGForce 3 graphicsShow the effect of network 26Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort-First vs Sort LastRandom Triangles27Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Sort First vs Sort LastTeapot28Angel: Interactive Computer Gra

19、phics 5E Addison-Wesley 2009Azul vs Intellistations29Angel: Interactive Computer Graphics 5E Addison-Wesley 2009Software for Parallel RenderingWrite your own sort-first sort-lastWireGL/Chromium (Stanford)Embed inside package (VTK)30Angel: Interactive Computer Graphics 5E Addison-Wesley 2009WireGL: A Distributed Graphics SystemA software-based parallel rendering system that unifies the rendering power of a collection of cluster nodesS