Lecture 11: Interactive Rendering Chapters 7 in Advanced GI

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1 Leture 11: Intertive endering Chpters 7 in Advned GI Questions? HW 1 Fll 2004 Kvit Bl Computer Siene Cornell University Intertive Softwre endering Intertive User-driven, not pre-sripted nimtion At lest few frmes per seond (fps) Softwre Mjor shding done in softwre Cn use hrdwre to help endering Online, not pre-omputed or ptured Eg, lightfields re pre-omputed An Oxymoron? Why not just use hrdwre? The gmes ll use it It hs lots of ool effets Isn t softwre too slow? Fst interpoltion from verties Speify properties t verties Color Texture oordintes Surfe normls, et. Interpolte t eh pixel in tringle Fst Visibility Determintion z-buffer: Amortized performne One rendering determines visible surfes for ll pixels simultneously But: verge tringle size is deresing Mny more visible tringles thn pixels, therefore, interpoltion less vluble

2 Fst Visibility Determintion Gret for some visibility queries types Primry (eye) rys Shdow rys (point soures) Not so good for other types Shdow rys (re light soures) Mny lights efletion & refrtion from urved surfes Indiret illumintion Adptive smpling Fst Shding Ltest bords n do per-pixel shding Progrmmble Lol shding only All inputs must be provided hed of time Non-lol shding n only be pproximted Shdows, refletions, indiret, et Why Softwre endering? Globl Illumintion: Non-lol informtion Extremely high omplexity Arbitrry shding models Portbility No tweking: just works No sene dependent optimiztions Hrdwre Vs. Softwre Hrdwre still hs the edge due to its dedited pipeline Softwre ttrtive for its slbility nd flexiblility If it n be mde fst enough for intertive use And hndle sene nd/or effets the hrdwre nnot hndle y Tring (or y Csting) Common visibility tool for softwre Flexible Effiient for lrge models Using n elertion struture (grids, bsp, et) Intertive T (Prker et. l.) SGI Origin proessors Shred memory Whitted-style ry tring Shdow, refletion, nd refrtion rys Usully the lrgest omputtionl bottlenek Esily prllelizble: eh pixel in prllel Non-polygonl primitives Spheres nd splines 15 fps

3 Intertive T: (Prker et l.) Dynmi lod blning Tsks divided by sreen region Sequene of lrger to smller tsks Found ner idel prllel speedup Coherent y Tring (Wld et. l.) Highly optimized ry tring engine for Intel-bsed PCs Crefully profiled their ry trer Disovered it ws often memory bound Hnd-rfted nd tuned their ode Both C nd ssembly versions Compt, he-friendly dt strutures Optimized for SIMD (SSE) eordered omputtions for better oherene Coherent y Tring (Wld et. l.) Optimiztions Seprted dt bsed on use Dt needed for intersetion stored seprtely Used ompt xis-ligned BSP struture Che ligned dt Works on groups of four rys t time Allows for effiient use of SIMD (SSE) Limittions estrited to tringles only Optimized for Phong shding speifilly Test Senes I Test senes: 800 tringles to >8 million Offie: 34,000 tringles, 3 lights Conferene oom: 280,000 tringles, 2 lights Test Senes II Test senes: 800 tringles to >8 million Berkeley Sod Hll: 1.5 to 8 million tringles Performne esults I Comprison to steriztion-hrdwre steriztion : IIS Performer TT: 512x512 Pixel, 1 CPU (PIII-800MHz) Terrin: 1 million tringles (textured) Sene (tringles) Otne Onyx3 NVidi Offie (40k) >24fps >36fps 12.7fps Thetre (680k) 0.4fps 6-12fps 1.5fps Librry (907k) 1.5fps 4fps 1.6fps 5 th floor (2.5M) 0.5fps 1.5fps 0.6fps Sod Hll (8M) TT 1.8fps 1.1fps 1.1fps 1.5fps 0.8fps

4 Performne esults II Comprison to steriztion-hrdwre y tring sles well for lrge environments Optimiztions (Wld et. l.) Also prllelized for more speed Demonstrted on five dul proessor PIIIs Times re for primry rys only Adding shdows, refletions, et. dds osts Considerble speedup But, more is needed, espeilly for more omplex shding suh s: soft shdows, glossy refletions, nd indiret illumintion Smple Imges Upshot Softwre Intertive endering is possible now with urrent mhines Good sling with sene omplexity Greter shding flexibility Mny more hllenges still remin Higher resolutions Anti-lising Fully dynmi environments Globl Illumintion Complex lighting Intertive Globl Illumintion

5 endering s Smpling y trers ompute rdine t eh pixel Coherene Within one frme: sptil oherene rdine rdine Frme 1 Frme 2 pixel number endering = Smpling rdine pixel number Aross mny frmes: temporl oherene Intertive Globl Illumintion Need to render every pixel of every frme? Strtegy Insight: rdine is mostly smooth -- use sprse smpling nd reonstrution rdine pek smooth disontinuity Frme 10 Frme 20 Frme 30 Exploit oherene in rdine objet spe, imge spe, temporl dine smples re very expensive Gol: reonstrut most pixels by interpoltion Issues: disontinuities, non-liner vritions Intertive Globl Illumintion Fst feedbk Must bridge gp in frmerte Intertive requirements Imge qulity esponsiveness Don t mke the user wit Provide rpid user feedbk Consisteny Don t surprise or distrt the user Avoid sudden hnges if possible Eg, in qulity, frme rte, popping, et. Visul Feedbk Loop Stndrd visul feedbk loop Entirely synhronous Frme-rte limited by renderer imge renderer pplition user

6 Modified Visul Feedbk Loop Disply Proess enderer Disply Imge User Automtilly exploit sptil nd temporl oherene Lyered on top of n existing (slow) globl illumintion renderer Provide intertive performne Applition Asynhronous interfe Sprse Smpling Approhes 4D: dine Interpolnts Holodek dine Interpolnts Bl(96,97,99) dine interpolnt: set of sprse smples of rdine funtion tht llow urte reonstrution 2D: Imge bsed Post-rendering Wrp ender Che Edge nd Point endering Note x-xis is the xis of rys Interpolnt for Approximtion y Prmeteriztion dine is omputed long ry In 2D, ry n be prmeterized by (,) y for pixel 2 Frme 0 y for pixel 1 Frme 0 y for pixel 2 Frme 1 y for pixel 1 Frme 1 Approximte rdine with onservtive error bounds: elerte ry tring Exploits sptil nd temporl oherene On-line: no preproessing

7 Dul Spe Linespe nd Interpolnts world spe - line spe Spe of rys is lled line spe It is dul spe Every ry in world spe is point in line spe And vie-vers world spe - line spe Biliner interpoltion = (1-)(1-) 00 + (1-) 10 + (1-) dine interpolnt: set of four rdine smples for region of line spe Dt struture: Linetree Linetree stores interpolnts for eh objet Hierrhil tree over line spe in 2D, qudtree Indexed by ry oordintes Given (,), find linetree lef nd its interpolnt (,) render pixel System Overview Interpolnt ry trer ollet rdine smples pproximte pixel rdine render filed pixels Interpolnt he - line spe Bse ry trer Model 3D ys: 4D Prmeteriztion y prmeterized by (,b,,d): 6 suh pirs of fes (,b) (,d) 4D dine Interpolnts Interpolnt ssoited with 4D hyperube in line spe Sixteen rdine smples Qudriliner interpoltion (,b) (,d) b d Linespe is 4D Every ry is point in 4D linespe A box in 4D linespe orresponds to bundle of 3D rys Smples stored in 4D linetree Error-driven subdivision b d

8 esults: Museum Sene ry-tring primitives (100k-500k polygons) 195 MHz Sprse Smpling Approhes 4D: dine Interpolnts Holodek 2D: Imge bsed Post-rendering Wrp ender Che Edge nd Point endering gry: interpoltion suess yellow: silhouettes; green: shdows; yn: non-liner rdine