Graphics Reference
In-Depth Information
potential
A
p
N
C
2
p
x
Δ
x
m
ψ
(
x
)=
p
=1
and then get the velocity field as
ψ.
u
=
∇×
The curl here can be approximated with finite differences for convenience,
rather than evaluated exactly. The simulation grid Δ
x
appears here to
emphasize that this should be done only for length scales below the simu-
lation.
In addition, the amplitude
A
p
of each octave of noise can be modulated
in space, allowing full control over where turbulence should appear. Bridson
et al. [Bridson et al. 07] in addition show that ramping
A
p
down to zero
at the boundary of a solid causes the velocity field to meet the solid wall
boundary condition.
All of these noise formulations can be animated in time, either using
4D noise functions or, more intriguingly, the FlowNoise method of Perlin
and Neyret [Perlin and Neyret 01].
