Einführung in Visual Computing

Transcription

1 Eführug Vsual Computg 868 Global Illumato Werer Purgathofer

2 Surface-Rederg Methods polygo rederg methods ray tracg global llumato evromet mappg teture mappg bump mappg Werer Purgathofer

3 Global Illumato the Rederg Ppele scee obects obect space trasformed vertces clp space scee ormalzed devce coordates raster mage pel coordates3 obect capture/creato modelg vewg proecto verte stage ( verte shader ) clppg + homogezato vewport trasformato rasterzato shadg pel stage ( fragmet shader )

4 Radosty Method descrbes the physcal process of lght dstrbuto a dffuse reflectg evromet areas that are ot llumated drectly are also ot completely dark every obect acts as a secodary lght source Werer Purgathofer 4

5 Radosty Radosty B s the radat flu per ut area that s leavg a surface Werer Purgathofer 5

6 Radosty Equato comg lght from the evromet radosty of the pot self emsso (oly for lght sources) reflected lght from evromet I() d = d B hem hem E d B hem B = E + hem d B Werer Purgathofer 6

7 Radosty Equato to calculate the lght fluece betwee surfaces Radosty = total lght leavg a surface pot B = E + hem d B B radosty E self emsso hem half space over pot reflecto coeffcet radosty = self emsso + reflecto property sum of all comg lght Werer Purgathofer 7

8 Radosty Propertes dffuse terreflectos a scee radat eergy trasfers coservato of eergy, closed evromets subdvso of scee to patches wth costat radosty B N φ dω ds db B = E + hem d B θ Werer Purgathofer 8

9 Radosty: Subdvso to Patches the scee s dscretzed to "patches" (plae polygos) P, for each of these patches a costat radosty B s assumed: B = E + hem d B B = E + Σ B F = dffuse reflecto coeffcet of patch F form factor : descrbes what % of the fluece o patch comes from patch ; = geometrc sze! Werer Purgathofer 9

10 Radosty Model B radosty of patch E self-emsso of patch ΣB F cotrbuto of other patches B = E + Σ B F = F form factor, defes cotrbuto of B o patch - whch s equal to cotrbuto of patch to B reflectvty coeffcet of patch ( albedo ) Werer Purgathofer 0

11 Werer Purgathofer Radosty Equato solvg the radosty equato + = B F E B E B F B = = E E E B B B F F F F F F

12 Werer Purgathofer Radosty Equato radostes (ukows) surface propertes surface propertes form factors (costats) = E E E B B B F F F F F F

13 Remder: Proecto of a Polygo a A θ θ a cosθ θ θ θ A cosθ Werer Purgathofer 3

14 Radosty: Form Factors F form factor F : cotrbuto of patch P to B = cotrbuto of B to patch P P P eergy reachg patch from patch total eergy leavg patch Werer Purgathofer 4

15 Radosty: Form Factors form factor F : cotrbuto of patch P to B = cotrbuto of B to patch P P P A φ φ r A ' F P P A φ A cosφ F = cosφ cosφ πr A because = = F Werer Purgathofer 5

16 Radosty: Form Factors form factor F : cotrbuto of patch P to B = cotrbuto of B to patch P P F = cosφ cosφ πr A more precsely: form factor s sum over cotrbutos from P averaged over area A A F = A A A πr Werer Purgathofer 6 cosφ cosφ da da

17 Radosty: Form Factors form factor propertes coservato of eergy = F = uform lght reflecto A F = A F o self-cdece F = 0 Werer Purgathofer 7

18 Radosty: Form Factors form factor calculato most epesve step radosty calculato umercal tegrato (Mote Carlo methods) hemcube approach (replaces hemsphere) P P P P Werer Purgathofer 8

19 Werer Purgathofer 9 Radosty Equato solvg the radosty equato Gaussa elmato Gauss-Sedel terato very tme ad storage tesve = E E E B B B F F F F F F

20 Radosty Equato solvg the radosty equato Gauss-Sedel terato B k+ = E + k B F B P gatherg Werer Purgathofer 0

21 Werer Purgathofer Radosty Equato gatherg vs shootg + + = k k B F E B + = + = P B P B

22 Progressve Refemet Radosty () shootg select brghtest patch P ad dstrbute ts radosty B B = E + B F B B due to B due to B = = B F B F because of A F = A F B due to B = B F A A Werer Purgathofer

23 Werer Purgathofer 3 select patch wth hghest A * B for selected patch { set up hemcube calculate form factors F } for each patch { rad := * B *F *A /A B := B + rad B := B + rad } B := 0 Progressve Refemet Radosty () [oe refemet step] B A A F B = due to B + =

24 Progressve Refemet Radosty (3) talze B =B =E select patch wth hghest B A cathedral redered wth progressve refemet radosty form factors computed wth ray-tracg methods Werer Purgathofer 4 by Joh Wallace & Joh L

25 Radosty Eample Images () mage of a costructvst museum redered wth progressve refemet radosty Corell Uv Werer Purgathofer 5

26 Radosty Results Werer Purgathofer 6

27 Radosty Results Werer Purgathofer 7

28 Radosty Results Werer Purgathofer 8 S Feldma, J Wallace

29 Radosty Eample Images (3) lghtg schemes for a opera producto: (left) day vew (rght) ght vew Werer Purgathofer 9

30 Radosty Aspects radosty s vewpot-depedet eeds a rederg step to dsplay polygo rederg Gouraud shadg ray-tracg combato wth ray-tracg eables reflectos shadows Werer Purgathofer 30 H Wa Jese

31 Radosty Results M Feda Werer Purgathofer 3

32 Global Illumato Improvemets/Varats herarchcal radosty reduces umber of form factors I Patazopoulos mesh desty vares wth mportace Werer Purgathofer 3

33 Global Illumato Improvemets/Varats dscotuty meshg mproves shadow boudares D Lschsk sharp shadow boudares get blurred by arbtrary meshg stay correct wth dscotuty meshg Werer Purgathofer 33

34 Dscotuty Meshg Eample dscotuty meshg allows for sharp shadows also Werer Purgathofer 34 D Lschsk

35 Radosty Eample Image star tower of a buldg at Corell Uversty redered wth progressve refemet radosty Werer Purgathofer 35

36 Global Illumato Improvemets / Varats path tracg R R T radom umbers P Werer Purgathofer 36 quas-radom umbers

37 Global Illumato Improvemets / Varats path tracg also called Mote Carlo ray tracg radomly selects ray drectos dstrbuto fuctos ( mportace samplg ) uses Mote Carlo tegrato to solve B = E + hem d B B radosty E self emsso hem half space over pot reflecto coeffcet Werer Purgathofer 37

38 Global Illumato Improvemets / Varats photo mappg trace lght rays from lght source(s) ad store llumato o obects 5 samples/pel 5 samples/pel 65 samples/pel Werer Purgathofer 38

39 Photo Mappg Eample caustcs from the er surface of a rg created wth photo mappg H Wa Jese Werer Purgathofer 39

40 Global Illumato Improvemets / Varats path tracg + photo mappg combed eable all surface propertes area lght sources / peumbras drect lghtg caustcs atalasg depth of feld moto blur Werer Purgathofer 40 VRVs