1 Temporal Radiance Caching P. Gautron K. Bouatouch S. Pattanaik.

1

Temporal Radiance Caching

P. Gautron K. Bouatouch S. Pattanaik

2

Global IlluminationGlobal Illumination

P

Lo(P, ωo) ∫ Li(P, ωi)= * BRDF(ωo, ωi) *cos(θ)dωi

3

GI: ComputationGI: Computation


No analytical solution

Numerical methods

- Radiosity

- Photon mapping- Path tracing- Bidirectional path tracing

- Irradiance & Radiance caching- …

4

GI: ComputationGI: Computation


No analytical solution

Numerical methods

- Radiosity

- Photon mapping

- Path tracing

- Bidirectional path tracing

- Irradiance & Radiance caching- …

5

(Ir)Radiance Caching(Ir)Radiance Caching

R

Spatial weighting function

Ward et al. 88: A Ray Tracing Solution for Diffuse Interreflections

6


Spatial gradients


7

(Ir)Radiance Caching(Ir)Radiance CachingWard et al. 88: A Ray Tracing Solution for Diffuse Interreflections

8


Record Location GI Solution


9

(I)RC in Dynamic Scenes(I)RC in Dynamic Scenes

10


11


12


13

ContributionsContributions

Temporal (ir)radiance interpolation scheme

Temporal weighting function

Temporal gradients

Fast estimate of future indirect lighting

14

OutlineOutline

- Introduction

- Irradiance and Radiance Caching

- Temporal Radiance Caching

- Results

- Conclusion

15

OutlineOutline

- Introduction



- Results

- Conclusion

16

Irradiance Caching: ObservationsIrradiance Caching: Observations

- Indirect lighting is costly

-Indirect lighting changes slowly over a surface


17

Irradiance Caching: PrincipleIrradiance Caching: Principle

Record Location GI Solution


18

IC Records: Zone of InfluenceIC Records: Zone of Influence

Close objects = Small zone Distant objects = Large zone

19

IC: Spatial Weighting FunctionIC: Spatial Weighting Function

Spatial change of indirect lighting depends on

- Local geometry

- Surrounding geometry

nk

n

PPk

20


nk

n

PPk

Upper bound of the change

change = ||P-Pk||

Rk

+ 1-n.nk

Distance Normals divergence

Mean dist. to the surrounding geometry

21


nk

n

PPk

wk(P) = 1

||P-Pk||

Rk

+ 1-n.nk

Distance Normals divergence

> 1/a

Mean dist. to the surrounding geometry

22

IC: Spatial GradientsIC: Spatial Gradients

No Gradients With Gradients

Estimate of the spatial change wrt.- Distance - Normals divergence

23

Radiance CachingRadiance Caching

Extension of irradiance caching to glossy interreflections

Cache directional distribution of light

Hemispherical Harmonics

Krivanek et al. 05: Radiance Caching for Efficient Global Illumination Computation

24

Radiance CachingRadiance Caching

Same weighting function as IC

Transl. gradient for each coef.

Rot. gradient replaced by rotation

Krivanek et al. 05: Radiance Caching for Efficient Global Illumination Computation

25


New cache for each frame

High cost

Flickering

Reuse records across frames

26

OutlineOutline

- Introduction



- Results

- Conclusion

- Temporal Weighting Function- Estimate of the Future Incoming Lighting- Temporal Gradients

27

OutlineOutline

- Introduction



- Results

- Conclusion


28

Temporal Weighting FunctionTemporal Weighting Function

Estimate the temporal change rate of indirect lighting

29



30



≈Et-Et+1

δt

∂E∂t

(t0)

= E0( -1)

= Et+1/Et

31


Inverse of the temporal change rate of indirect lighting

= Et+1/Et

( -1)(t-t0)

1wk

t(t) = > 1/at

Problem : Lifespan is determined when the record is created

32

Lifespan ThresholdingLifespan Thresholding

P

At point P and time t:

Static environment

= Et+1/Et = 1

wkt(t) = ∞ for all t

Infinite Lifespan

33


P


Static environment

= Et+1/Et = 1


Infinite Lifespan

34


P


Static environment

= Et+1/Et = 1


Infinite LifespanIncorrect

wkt(t) = 0 if t-tk>δtmax

35

Record ReplacementRecord Replacement

36


Determines the lifespan of the records

Lifespan depends on the local change of incoming radiance

If the environment is static, threshold the lifespan to a maximum value

= Et+1/Et

Requires the knowledge of future irradiance

However

37

OutlineOutline

- Introduction



- Results

- Conclusion


38

Future Incoming LightingFuture Incoming Lighting

P P

≈Time t Time t+1

E(P, t) = E(P, t+1) =

39


Assumption: Animation is predefined

Future transformation matrices are known

Use reprojection to estimate the future incoming lighting

40

ReprojectionReprojection

k

Et

Et+1

41


t+1t

k

EtOK

Et+1

Hemispheresampling

42


t+1

? ?

EtOK

Et+1

Reprojection

43


EtOK

Et+1

t+1

? ?

Depth culling

44


EtOK

Et+1

Hole filling

t+1

? ?

45


EtOK

Et+1

t+1

OK

46


Simple reprojection

No additional hemisphere sampling

Easy GPU Implementation

47

Temporal InterpolationTemporal Interpolation

k

Et =

48

Temporal InterpolationTemporal Interpolation

k

Et = Recompute Irradiance

49

Temporal Interpolation: GoalTemporal Interpolation: Goal

k

Et =

50

OutlineOutline

- Introduction



- Results

- Conclusion


51

Extrapolated GradientsExtrapolated Gradients

Et computed by hemisphere sampling

Et+1 estimated by reprojection

Δ

textra ≈ Et+1-Et

Δ

t = ∂E / ∂t

52


k

Etextra = E0 = Computed

E1 = EstimatedEt

actual =

Etactual-Et

extra =

53


54

Interpolated Gradients: Pass 1Interpolated Gradients: Pass 1

k

E0 = Computed

Etactual =

55

Interpolated Gradients: Pass 2Interpolated Gradients: Pass 2

k

Etinter = E0 = Computed

Et = ComputedEt

actual =

Etactual-Et

inter =

56

Interpolated GradientsInterpolated Gradients

Et computed by hemisphere sampling

Et+n computed by hemisphere sampling

Δ

t = ∂E / ∂t

Δ Et+n-Et

ntinter ≈

57

Temporal GradientsTemporal Gradients

Extrapolated

1 pass

Possible flickering

Interpolated

2 passes

No flickering

58

OutlineOutline

- Introduction



- Results

- Conclusion

59

Flying KiteFlying Kite

60

Japanese InteriorJapanese Interior

61

Japanese InteriorJapanese Interior

62

SpheresSpheres

63

ConclusionConclusion

Temporal radiance interpolation scheme

Reuse records across frames

Quality improvement Speedup

Easily integrates within (ir)radiance caching-based renderers

GPU ImplementationWork submitted for publication

Dynamic objects, light sources, viewpoint

64

Future WorkFuture Work

Avoid the need of maximum lifespan

Propose an interpolation method adapted to fast changes(temporal details are smoothed out by the gradients)

65

On the web:http://www.irisa.fr/siames/Pascal.Gautron/

ORGoogle ‘pascal gautron’

P. Gautron, K. Bouatouch, S. Pattanaik

Temporal Radiance Caching

Technical Report no. 1796, IRISA, Rennes, France

1 Temporal Radiance Caching P. Gautron K. Bouatouch S. Pattanaik.

Documents

Transcript of 1 Temporal Radiance Caching P. Gautron K. Bouatouch S. Pattanaik.