PBRT core. Announcements. pbrt. pbrt plug-ins

Transcription

1 Announcements PBRT core Dgtal Image Synthess Yung-Yu Chuang 9/27/2007 Please subscrbe the malng lst. Wndows complaton Debuggng n Wndows Doxygen (onlne, download or doxygen by yourself) HW#1 wll be assgned next week (10/4) and due on 10/25. wth sldes by Pat Hanrahan pbrt pbrt plug-ns pbrt (physcally-based ray tracng) attempts to smulate physcal nteracton between lght and matter based on ray tracng. A plug-n archtecture: core code performs the man flow and defnes the nterfaces to plug-ns. Necessary modules are loaded at run tme as DLLs, so that t s easy to extend the system.

2 Example scene LookAt Camera "perspectve" "float fov" [30] PxelFlter "mtchell" "float xwdth" [2] "float ywdth" [2] Sampler "bestcanddate" Flm "mage" "strng flename" ["test.exr"] "nteger xresoluton" [200] "nteger yresoluton" [200] renderng optons # ths s a meanngless comment WorldBegn d type param-lst AttrbuteBegn CoordSysTransform "camera" type name [value] LghtSource "dstant" "pont from" [0 0 0] "pont to" [0 0 1] "color L" [3 3 3] AttrbuteEnd Example scene AttrbuteBegn Rotate Texture "checks" "color" "checkerboard" "float uscale" [8] "float vscale" [8] "color tex1" [1 0 0] "color tex2" [0 0 1] Materal "matte" "texture Kd" "checks" Shape "sphere" "float radus" [20] AttrbuteEnd WorldEnd Phases of executon man() n renderer/pbrt.cpp nt man(nt argc, char *argv[]) { <Prnt welcome banner> pbrtint(); // Process scene descrpton f (argc == 1) { // Parse scene from standard nput ParseFle("-"); else { // Parse scene from nput fles for (nt = 1; < argc; ++) f (!ParseFle(argv[])) Error("Couldn't open \"%s\"\n", argv[]); pbrtcleanup(); return 0; Scene parsng core/pbrtlex.l and core/pbrtparse.y After parsng, a scene object s created (core/scene.*) aggregate class scene { Prmtve *aggregate; vector<lght *> lghts; prmtve prmtve Camera *camera; (contans a flm) shape VolumeRegon *volumeregon; SurfaceIntegrator *surfaceintegrator; VolumeIntegrator *volumeintegrator; Sampler *sampler; (generates sample postons BBox bound; for eye rays and ntegrators) ; materal

3 Renderng Scene::Render() s nvoked. Scene::Render() whle (sampler->getnextsample(sample)) { RayDfferental ray; float rayw=camera->generateray(*sample,&ray); <Generate ray dfferentals for camera ray> float alpha; opacty along the ray Spectrum Ls = 0.f; f (rayw > 0.f) Ls = rayw * L(ray, sample, &alpha); camera->flm->addsample(*sample,ray,ls,alpha); Scene::L Spectrum Scene::L(RayDfferental &ray, Sample *sample, float *alpha) { Spectrum Lo=surfaceIntegrator->L( ); Spectrum T=volumeIntegrator->Transmttance( ); Spectrum Lv=volumeIntegrator->L( ); return T * Lo + Lv; Renderng equaton ω o L o ( p,ωo) 5D lght feld p,ω ) ( L p ω Lv T L o L ( o p,ωo) = L e ( p,ωo) + s f (p,ωo,ω ) L (p,ω ) cosθ 2 d ω

4 Surface ntegrator Whtted model Whtted ntegrator n ntegrators/whtted.cpp class WhttedIntegrator:publc SurfaceIntegrator Spectrum WhttedIntegrator::L(Scene *scene, RayDfferental &ray, Sample *sample, float *alpha) { bool htsomethng=scene->intersect(ray,&sect); f (!htsomethng) {nclude effects of lghts wthout geometry else { <Computed emtted and reflect lght at sect> Whtted ntegrator BSDF *bsdf=sect.getbsdf(ray); n ω ω Vector wo=-ray.d; o L+=sect.Le(wo); p Vector w; drect lghtng for (u_nt = 0; < scene->lghts.sze(); ++) { VsbltyTester vsblty; Spectrum L = scene->lghts[]-> Sample_L(p, &w, &vsblty); f (L.Black()) contnue; Spectrum f = bsdf->f(wo, w); f (!f.black() && vsblty.unoccluded(scene)) L += f * L * AbsDot(w, n) * vsblty.transmttance(scene);

5 Whtted ntegrator f (raydepth++ < maxdepth) { Spectrum f = bsdf->sample_f(wo, &w, BxDFType(BSDF_REFLECTION BSDF_SPECULAR)); f (!f.black()) { <compute rd for specular reflecton> L += scene->l(rd, sample) * f * AbsDot(w, n); f = bsdf->sample_f(wo, &w, BxDFType(BSDF_TRANSMISSION BSDF_SPECULAR)); f (!f.black()) { <compute rd for specular transmsson> L += scene->l(rd, sample) * f * AbsDot(w, n); Code optmzaton Two commonly used tps Dvde, square root and trgonometrc are among the slowest (10-50 tmes slower than +*). Multplyng 1/r for dvdng r. Beng cache conscous Cache-conscous programmng alloca AllocAlgned(), FreeAlgned() make sure that memory s cache-algned Cache-conscous programmng Arena-based allocaton allows faster allocaton and better localty because of contguous addresses. Blocked 2D array, used for flm w w Use unon and btfelds to reduce sze and ncrease localty Splt data nto hot and cold h. h..