Transient Rendering Adam Smith James Skorupski University of - - PowerPoint PPT Presentation

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Transient Rendering Adam Smith James Skorupski University of - - PowerPoint PPT Presentation

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Transient Rendering Adam Smith James Skorupski University of California, Santa Cruz December 11, 2007 CMPS 290B {amsmith,jskorups}@cs.ucsc.edu 2/32 Motivation There is growing interest in time-of-flight based computer vision applications

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SLIDE 1

Transient Rendering

Adam Smith James Skorupski

University of California, Santa Cruz December 11, 2007 CMPS 290B {amsmith,jskorups}@cs.ucsc.edu

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SLIDE 2

Motivation

There is growing interest in time-of-flight based computer vision applications and we want some general, physical explanation of measurements we make. Our contribution: a formal model that let’s us do just that

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SLIDE 3

Background

  • We want

▫ Rigorous analysis ▫ Specific to light ▫ Transient effects

  • What’s out there

▫ LIDAR ▫ SONAR ▫ Rendering Equation

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SLIDE 4

LIDAR

  • NO: Rigorous analysis
  • YES: Specific to light
  • YES: Transient effects

(UC Santa Cruz) (UC Davis) 4/32

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SLIDE 5

SONAR

  • YES: Rigorous analysis
  • NO: Specific to light
  • YES: Transient effects

(USGS) (NOAA) Height field of two sunken ships Overview (Transponder in yellow) 5/32

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SLIDE 6

Rendering Equation

  • YES: Rigorous analysis
  • YES: Specific to light
  • NO: Transient effects

where

▫ L is total light ▫ L0 is emitted light ▫ G is global transport (single bounce)

(Kajiya, 1986) (Stanford) 6/32

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SLIDE 7

The Important Distinction

Steady state vs. transient light transport

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SLIDE 8

Visualization

  • Steady state: Where the light comes out

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SLIDE 9

Visualization

  • Transient: When the light comes out

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SLIDE 10

Visualization

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SLIDE 11

Visualization

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SLIDE 12

Visualization

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SLIDE 13

Visualization

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SLIDE 14

Visualization

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SLIDE 15

Visualization

  • Note: Top pulse wins the race!

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SLIDE 16

Energy vs. Power

Steady State Transient Energy (Joules) Power (Watts) Number of photons received Rate of photons received Radiance Radiant flux

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SLIDE 17
  • X, Y are points
  • c is the speed of light

Infinite vs. Finite

  • D

Steady State Transient

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SLIDE 18

Functions

  • X is a point
  • ω is a direction
  • t is a time

Steady State Transient

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SLIDE 19

Transient Rendering Equation

(our contribution)

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SLIDE 20

Transient Rendering Equation

  • Global light transport G is the composition of

two physical processes

▫ propagation, P

 delays light over distances

▫ scattering, S

 same as traditional rendering

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SLIDE 21

Example

a) 1-d world with two surfaces A and B, eye E and light L b) result of transient rendering c) light seen at E over time

  • Input: positions, scattering

kernels, initial light emission

  • Output: received light

power at every point, every direction, and every time

a) b)

A B E L Z

c)

Time Time

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SLIDE 22

Example

a) 1-d world with two surfaces A and B, eye E and light L b) result of transient rendering c) light seen at E over time

  • Input: positions, scattering

kernels, initial light emission

  • Output: received light

power at every point, every direction, and every time

a) b)

A B E L Z

c)

Time Time

22/32

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SLIDE 23

Example

a) 1-d world with two surfaces A and B, eye E and light L b) result of transient rendering c) light seen at E over time

  • Input: positions, scattering

kernels, initial light emission

  • Output: received light

power at every point, every direction, and every time

a) b)

A B E L Z

c)

Time Time

23/32

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SLIDE 24

Example

a) 1-d world with two surfaces A and B, eye E and light L b) result of transient rendering c) light seen at E over time

  • Input: positions, scattering

kernels, initial light emission

  • Output: received light

power at every point, every direction, and every time

a) b)

A B E L Z

c)

Time Time

24/32

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SLIDE 25

Example

a) 1-d world with two surfaces A and B, eye E and light L b) result of transient rendering c) light seen at E over time

  • Input: positions, scattering

kernels, initial light emission

  • Output: received light

power at every point, every direction, and every time

a) b)

A B E L Z

c)

Time Time

25/32

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SLIDE 26

Sensor Model

  • Turns ideal worlds into ground truth sensor

readings

  • Takes into account:

▫ Sampled function of time ▫ Integration over shutter window ▫ Light pulse envelope ▫ Discrete photons

  • Produces: sequence of energy measurements

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SLIDE 27

New Research Directions

  • Applications: do things we could not do before
  • Building sensors: capture transient patterns

directly

  • Theory: generalize and compute

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SLIDE 28

Some Applications

  • 3.0D range finding (hidden surfaces)
  • Subsurface scattering estimation from time

instead of space samples

  • Model-based LIDAR applications

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SLIDE 29

Building Sensors

  • Existing LIDAR hardware measures the data we

need, but throws most of it away

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SLIDE 30

Theory

  • Generalize

▫ Wavelength ▫ Subsurface scattering ▫ Phosphorescence

  • Compute

▫ Dependency calculation ▫ Function representations ▫ Augment a common raytracer

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SLIDE 31

Theory

  • Generalize

▫ Wavelength ▫ Subsurface scattering ▫ Phosphorescence

  • Compute

▫ Dependency calculation ▫ Function representations ▫ Augment a common raytracer

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SLIDE 32

Conclusion

We have taken initial steps into exploring the effects of the light propagation delay, and called this Transient Rendering. We hope that transient rendering can serve as a principled foundation for future time-of-flight based computer vision techniques.

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