A Hierarchical Volumetric Shadow

A Hierarchical Volumetric Shadow A Hierarchical Volumetric Shadow - Start

2016-05-05 38K 38 0 0

A Hierarchical Volumetric Shadow - Description

Algorithm for Single Scattering. Ilya. . Baran. , . Jiawen. Chen, Jonathan Ragan-Kelley,. Frédo Durand, . Jaakko. . Lehtinen. Computer Science and Artificial Intelligence Laboratory. Massachusetts Institute of Technology. ID: 306444 Download Presentation

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A Hierarchical Volumetric Shadow




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Presentations text content in A Hierarchical Volumetric Shadow

Slide1

A Hierarchical Volumetric ShadowAlgorithm for Single Scattering

Ilya Baran, Jiawen Chen, Jonathan Ragan-Kelley,Frédo Durand, Jaakko LehtinenComputer Science and Artificial Intelligence LaboratoryMassachusetts Institute of Technology

Slide2

Volumetric scattering with shadows

Photo by Frédo Durand

Slide3

Alan Wake

by Remedy Entertainment

Slide4

Slide5

Slide6

Slide7

Slide8

Related work

Ray marching(brute force)Analytical scattering modelsSky lighting, bloom, etc.Doesn’t account for visibility

Sun et al. [2005]

Slide9

Shadow volume methods

Max [1986]Analytical integrationWyman and Ramsey [2008]Ray marching along intervals

Slide10

Related work

Engelhardt and Dachsbacher [2010]Detect discontinuities, subsample and interpolatePerformance depends on occluder complexityEpipolar geometry

Detected

discontinuties

Engelhardt

and

Dachsbacher

[2010]

Slide11

Overview

Incremental integrationApproximating single scatteringEpipolar rectification

~

Slide12

Simplified scenario

Orthographic camera

Light direction perpendicular to view direction

Visibility only

Slide13

r

d

Slide14

Slide15

7

5

Brute force complexity:

O(

rd

)

1

Slide16

7

5

5

1

Brute force complexity:

O(

rd

)

Slide17

1

1

1

1

1

1

1

Bit mask

Process top down incrementally

Slide18

7

1

1

1

1

1

1

1

Bit mask

Slide19

7

1

1

1

1

1

1

1

1

Bit mask

Slide20

7

1

1

1

1

1

1

1

1

Bit mask

Slide21

7

1

1

0

0

1

1

1

1

Bit mask

Slide22

7

1

5

1

0

0

1

1

1

1

Bit mask

Slide23

7

1

5

Bit mask algorithm complexity:

O(

rd

)

5

2

2

3

1

0

0

1

1

1

1

Bit mask

Slide24

Partial sum trees

Binary treeEach node storessum of children

4

2

2

2

0

1

1

1

1

0

0

1

0

1

0

Slide25

Tree update

4

2

2

2

0

1

1

1

1

0

0

0

0

1

0

Slide26

Tree update

4

2

2

2

0

0

1

1

1

0

0

0

0

1

0

Slide27

Tree update

4

2

1

2

0

0

1

1

1

0

0

0

0

1

0

Slide28

Tree update

3

2

1

2

0

0

1

1

1

0

0

0

0

1

0

Slide29

Tree query

3

2

1

2

0

0

1

1

1

0

0

0

0

1

0

∑ = 3

Slide30

Complexity

2D

Brute force:

O(

rd

)

Incremental with bit mask:

O(

rd

)

Incremental with tree:

O( (

r+d

) log d )

3D:

s

independent

slices

Brute force:

O(

srd

)

Incremental with tree:

O(

s (

r+d

) log d )

Slide31

Textured lights

0.8

0.1

0.5

0.3

0.2

1

0.8

Light texture

1

0.9

0.8

0.6

0.5

0.4

0.3

Light attenuation

Slide32

SVD approximation

~

A

U

SV

T

=

+

+

+

Slide33

Epipolar

rectification

Light direction

Epipolar

slices

Eye

Slide34

Epipolar coordinates

Point light

Directional light

Slide35

Depth map resampling

Camera depth map

Light depth map

Rectify

Rectify

Corresponding

epipolar

slice

 

 

 

 

Slide36

9.9 sec (17.1x)

169 sec

Equal quality comparison:

Sibenik

Our method

Ray marching

Slide37

Our method

Ray marching

Equal quality comparison: Terrain

1.3 sec (41.5x)

54 sec

Slide38

Equal quality comparisons: Trees

Our method

Ray marching

2.3 sec (120.4x)

277 sec

Slide39

Slide40

GPU Performance on

Sibenik

Slide41

GPU Performance on Trees

Slide42

Limitations and future work

Non-homogeneous media

All points in volume must be visited

SVD will have high rank

GPU performance

Dynamic data structure: limited parallelism

Bandwidth intensive

Requires CUDA, not suitable for consoles

Slide43

Summary

Hierarchical volumetric shadow algorithm with complexity guaranteesSignificant speedupson CPUsModerately faster than state-of-the art on GPUs

Slide44

GPU Performance on Sibenik

Slide45

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Slide47


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