Interactive Rendering of Atmospheric Scattering Effects Using Graphics Hardware

1
Interactive Rendering of Atmospheric Scattering
Effects Using Graphics Hardware
Hokkaido University
Yoshinori Dobashi
Tsuyoshi Yamamoto
Hokkaido University
Tomoyuki Nishita
Tokyo University
2
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Conclusion

3
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Results

• Conclusion

• Conclusion

4
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Conclusion

5
Motivation

• Real-time rendering of realistic images

• Atmospheric Scattering Effects

• scattering and absorption of light due to
  small particles

• spotlights
• sunlight through windows
• earths atmosphere

requires long computation time

• Our Goal

Real-time rendering of atmospheric effects
6
Previous Work

• use of voxels to store the intensity of light

• consuming texture memory for volume data

• difficult to capture the edges of shafts of light

7
Previous Work

• use of shadow and projective texture mapping

• artifacts due to sampling errors

• a general and efficient solution to the
  sampling problem

• not optimal for rendering atmospheric scattering

• Earths atmosphere

• no methods for real-time rendering of realistic
  images

8
Proposed Method

• Precise and efficient rendering of atmospheric
  effects

• Rendering light beams

• point/infinite light sources

• uniform density of atmospheric particles

• Rendering earths atmosphere

• sky

• the earth viewed from space

• density decreases exponentially according to
  the height from the ground

9
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Conclusion

10
Shading Model for Light Beams
Intensity at viewpoint
point source
Ieye
viewpoint
11
Shading Model for Light Beams
Intensity at viewpoint
point light
Is
viewpoint
12
Basic Idea
Dobashi00
Intensity at viewpoint
computed at lattices
13
Basic Idea
Dobashi00
Intensity at viewpoint
n
å


k
1
14
Basic Idea
Dobashi00
Intensity at viewpoint
n
å


k
1
15
Basic Idea
Dobashi00
Intensity at viewpoint
n
å


k
1
object
shadow mapping
render sampling planes with additive blending
16
Problems

• Many planes/lattices for high quality image

• artifacts due to quantization errors

• quantization with 8 bit precision in most
  hardware

• accumulation of errors in proportion to number
  of sampling planes

• increase in rendering time

17
High Quality Rendering
Intensity at viewpoint
18
High Quality Rendering
point light
Intensity at viewpoint
Il
t
P
Dt
Is
19
High Quality Rendering
point light
Intensity at viewpoint
Il
t
P
Dt
Is
20
High Quality Rendering
point light
Intensity at viewpoint
1.0
Il
Is
scattering component
21
High Quality Rendering
point light
Intensity at viewpoint
Il
ratio of reached light
Is
scattering component
Illumination component
22
High Quality Rendering

• changes smoothly

• can be sampled at a large interval

use of texture to store pre-integrated values

• includes visibility H and intensity distribution
  Il

• must be sampled at a short interval

sub-planes for accurate sampling
23
High Quality Rendering

• changes smoothly

• can be sampled at a large interval

use of texture to store pre-integrated values

• includes visibility H and intensity distribution
  Il

• must be sampled at a short interval

sub-planes for accurate sampling
24
Textures for Scattering Component
(point light)
25
Textures for Scattering Component
(point light)
point light

• local coordinate UV

sampling plane k1
sampling plane k
s
t
a
tk
P
P(u, v)
viewpoint
P
P(u, v)
Dt
26
Textures for Scattering Component
U
point light
sampling plane k1
sampling plane k
s
Q
t
a
V
fl is evaluated precisely since texture stores
integrated values
tk
P(u, v)
viewpoint
P(u, v)
Dt
27
High Quality Rendering

• changes smoothly

• can be sampled at a large interval

use of texture to store pre-integrated values

• includes visibility H and intensity distribution
  Il

• must be sampled at a short interval

sub-planes for accurate sampling
28
Computation of Illumination Component

• mk sub-planes between sampling planes k and k1

viewpoint

• mk is determined adaptively

29
Computation of Illumination Component

• Determining number of sub-planes, mk

1. shoot a ray
2. compute intensity of scattered light
3. generate sub-planes in proportion to
intensity
viewpoint
same contribution of each sub-plane to pixel
intensity
30
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Conclusion

31
Rendering Earths Atmosphere

• No shadows of objects

• Rendering Sky

• extending method for light beams

• Rendering the earth viewed from space

32
Rendering Earths Atmosphere

• No shadows of objects

• Rendering Sky

• extending method for light beams

viewpoint
atmosphere

• Rendering the earth viewed from space

• atmosphere is very thin layer covering the
  earth

earth
33
Rendering Earths Atmosphere

• No shadows of objects

• Rendering Sky

• extending method for light beams

viewpoint
atmosphere

• Rendering the earth viewed from space

• atmosphere is very thin layer covering the
  earth

earth

• use of sampling spheres instead of sampling
  plane

34
Rendering Earths Atmosphere

• No shadows of objects

• Rendering Sky

• extending method for light beams

• Rendering the earth viewed from space

• atmosphere is very thin layer covering the
  earth

• use of sampling spheres instead of sampling
  plane

35
Rendering Sky

• Intensity at viewpoint

36
Rendering Sky

• Intensity at viewpoint

37
Rendering Sky

• Intensity at viewpoint

Ps
P
38
Rendering Sky

• Intensity at viewpoint

• Algorithm

• create textures of gl , Dgv , R

Pv

• for k n to 1, repeat

viewpoint

• map gl , Dgv , R textures onto sampling plane k

earth
39
Rendering Sky

• Intensity at viewpoint

• Algorithm

• create textures of gl , Dgv , R

Pv

• for k n to 1, repeat

viewpoint

• map gl , Dgv , R textures onto sampling plane k

earth

• compute IsunF at lattice points

40
Rendering Sky

• Intensity at viewpoint

• Algorithm

• create textures of gl , Dgv , R

Pv

• for k n to 1, repeat

viewpoint

• map gl , Dgv , R textures onto sampling plane k

earth

• compute IsunF at lattice points

• draw plane with blending

41
Rendering Sky

• Intensity at viewpoint

• Algorithm

• create textures of gl , Dgv , R

Pv

• for k n to 1, repeat

viewpoint

• map gl , Dgv , R textures onto sampling plane k

earth

• compute IsunF at lattice points

• draw plane with blending

42
Rendering Sky

• Textures of gl, Dgv , R

Ps
atmosphere
Pv
viewpoint
P
h
earth
43
Rendering Sky

• Textures of gl, Dgv , R

Ps
atmosphere
s
Pv
viewpoint
P
earth
44
Rendering Sky

• Textures of gl, Dgv , R

Ps
atmosphere
Pv
viewpoint
P
h
earth
45
Overview

• Introduction

• motivation
• previous work

• Rendering Light Beams

• basic Idea
• problems
• high quality rendering

• Rendering the Earths Atmosphere

• rendering sky
• rendering the earth viewed from space

• Results

• Conclusion

46
Experimental Results
previous method
previous method
proposed method
planes 40 mesh 60x60
planes 160 mesh 60x60
planes 30 sub-planes 120 (ave.) mesh 10x10
computer Athlon 1.7GHz, GeForce3
47
Experimental Results
Image size 300x450
computer Athlon 1.7GHz, GeForce3
48
Experimental Results
interleaved Keller01
ray-tracing
method
previous
proposed
result
of planes (sub-planes)
-
40
160
23 (174)
mesh
-
60x90
10x15
10x15
time
0.13 sec.
29 sec.
0.12 sec.
0.08 sec.
Image size 300x450
computer Athlon 1.7GHz, GeForce3
49
Results
50
Results
sampling plane 100(sky)
30(shaft) sub-plane135
sampling sphere 10
time 0.06 sec.
time 0.16 sec.
51
DEMO

• Real-time Animation Using Note PC

• Pentium III (1.2 GHz)
• Nvidia GeForce 2 Go

52
Conclusion

• Fast rendering of atmospheric effects

• Rendering of light beams

• 2D textures to store intensities of scattered
  light

• sub-planes for precise sampling of shadows

• Extension to rendering earths atmosphere

• rendering of sky

• rendering of earth viewed from space