Realtime Rendering of Aerodynamic Sound Using Sound Textures based on Computational Fluid Dynamics

1
Real-time Rendering of Aerodynamic Sound Using
Sound Textures based on Computational Fluid
Dynamics
2
Examples of aerodynamic sound

• Sound of wind

• Sound generated by swinging objects quickly

3
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

4
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

5
Introduction

• Simulation of virtual environments

• Sound important element

• voice, contact sound, etc.

• Improving reality of virtual environments

• Use of recorded sound

• need to find suitable sound

• quality depends on environment

6
Introduction

• Physically-based sound synthesis

• compute waves based on physical simulation

• generate sound automatically according to
  object motion

• Limited to sound due to solid objects

• Sound due to fluid

• wind(aerodynamic sound), water, explosion ...

7
Goal and Feature

• Real-time rendering of aerodynamic sound

• source is not oscillation of solid objects

• creating sound textures for aerodynamic sound

• rendering sound in real-time according to
  object motion

8
Goal and Feature

• Sound by swinging sword and club

• Real-time sound rendering
• Sound synthesis depending on shapes and motion
  of objects

9
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

10
Related Work in CG
Takala92 Funkhouser99 Tsingos01

• Propagation of sound

• simulate reflection/absorption due to objects
  to compute sound taking into account geometric
  relation between source and receiver

Hahn95OBrien01OBrien02van den doel01

• Synthesis of sound waves

• compute sound waves by numerical analysis of
  subtle oscillation of objects

• No methods for aerodynamic sound

11
Related Work in CFD

• Prediction of aerodynamic sound

Lele97

• to reduce noise due to high-speed
  transportation facilities, etc.

• complex numerical fluid simulation

• not appropriate for real-time applications

• Our method

• Makes use of methods developed in CFD
• Realizes real-time sound synthesis

12
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

13
Principle and Prediction

• Source of aerodynamic sound

vortices

• vortices in air

• subtle fluctuations of air pressure due to
  vortices

• Prediction method

• Lighthills basic theory in 1952

Ligh52

• numerical simulation of compressible
  Navier-Stokes equations

? computationally expensive

• Curles model

14
Curles Model

• Prediction by behavior of air near object

15
Curles Model

• Prediction by behavior of air near object

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Curles Model

• Prediction by behavior of air near object

sound source function (SSF)
normal
pressure
g(t) (x component)
17
Curles Model

• Prediction by behavior of air near object

sound source function (SSF)
18
Curles Model

• Prediction by behavior of air near object

sound source function (SSF)
19
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

20
Basic Idea

• Use of Curles model

• not applicable to large object

• subdivide object into small regions

• equivalent to assuming independent virtual
  point sound sources

21
Basic Idea

• Computing sound texture (preprocess)

• Rendering aerodynamic sound (real-time)

22
Basic Idea

• Computing sound texture (preprocess)

• fluid analysis

? table of sound source func.

• Rendering aerodynamic sound (real-time)

23
Basic Idea

• Computing sound texture (preprocess)

• fluid analysis

? table of sound source func.

• Rendering aerodynamic sound (real-time)

24
Basic Idea

• Computing sound texture (preprocess)

• fluid analysis

? table of sound source func.

• Rendering aerodynamic sound (real-time)

• dir./speed

?values of SSF
?sound texture
SSF values (g1, g2, , gn)
receiver pos. q
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Basic Idea

• Computing sound texture (preprocess)

• fluid analysis

? table of sound source func.

• Rendering aerodynamic sound (real-time)

• dir./speed

?values of SSF
?sound texture
? sound pressure
?Curles model
SSF values (g1, g2, , gn)
Curles model
receiver pos. q
26
Basic Idea

• Computing sound texture (preprocess)

• fluid analysis

? table of sound source func.

• Rendering aerodynamic sound (real-time)

• dir./speed

?values of SSF
?sound texture
? sound pressure
?Curles model
SSF values (g1, g2, , gn)
Curles model
receiver pos. q
27
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

28
Computation of Sound Texture

• Fluid analyses for many directions and speeds

• long computation time

29
Computation of Sound Texture

• Properties of aerodynamic sound

• frequency ? flow speed v
• amplitude ? (flow speed v )6

• Need only sound texture at base speed v0

• Reduce computation time and memory requirement
  drastically

30
Choosing 2D or 3D Fluid Analysis
Stick-like object
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Choosing 2D or 3D Fluid Analysis
speed v
time
v0
sound source pos.
1D sound tex.
32
Choosing 2D or 3D Fluid Analysis
Stick-like object
2D sound tex.
1D sound tex.
2D analysis
Others
2D sound tex.
33
Choosing 2D or 3D Fluid Analysis
2D sound tex.
3D analysis
34
Choosing 2D or 3D Fluid Analysis
2D sound tex.
3D sound tex.
3D analysis
35
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

36
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
37
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
1. compute direction ci and speed vi
38
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
1. compute direction ci and speed vi
2. compute SSF gi
39
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
1. compute direction ci and speed vi
2. compute SSF gi
3. compute distance ri to receiver
40
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
1. compute direction ci and speed vi
2. compute SSF gi
3. compute distance ri to receiver
4. compute sound pressure pv
Curles model
41
Real-time Sound Rendering

• Procedure

- repeat for each time step Dt
1. compute direction ci and speed vi
2. compute SSF gi
3. compute distance ri to receiver
4. compute sound pressure pv
42
Computation of SSF

• Property

• freq. ? speed v
• amp. ? (speed v )6

43
Computation of SSF
vi
actual speed
vi(k)
Dt
k
t
s
w
sound texture (base speed v0)
44
Computation of SSF
vi
actual speed
vi(k)
Dt
k
t
x(vi(k)/v0)6
s
vi(k)/v0xDt
w
sound texture (base speed v0)
45
Computation of SSF
vi
actual speed
Dt

• Recurrence relation

t
s
w

• Periodical use

• blending for smooth transition

sound texture (base speed v0)
46
Overview

• Introduction
• Related Work
• Principle and Prediction of Aerodynamic Sound
• Basic Idea of Our Method
• Computation of Sound Texture
• Real-time Sound Rendering
• Examples
• Conclusions

47
Fluid Simulation Demo

• Sound texture for square prism for one
  direction of flow

• length 50cm, side length 2.0cm
• base speed 10 m/s
• 2D analysis
• finite difference

48
Real-time Sound Rendering Demo
49
Application

• Character animation

• Bear swinging a huge club
• Warrior swinging two different swords

(image by TAITO)
50
Conclusions

• Sound synthesis of fluid

• Real-time rendering of aerodynamic sound

• sound texture based on CFD

• synthesis of sound waves using Curles model

• real-time

• New element to improve realistic simulation of
  virtual environments

51
Acknowledgement

• As for fluid analysis

Atsushi Kunimatu (TOSHIBA Corp., Japan), Tunemi
Takahashi (TOSHIBA Corp., Japan), Naofumi Shibata
(TOSHIBA Info. Systems Corp., Japan)

• As for character animation

• People of GARAKUTA STUDIO (TAITO Corp., Japan)

• People of Project BUJINGAI (TAITO Corp., Japan)