Smoke Simulation with Two-Scale Vorticity Confinement - Multimedia and Signal Processing - page 470

forces (buoyancy, vorticity
We need additional storage
On fine grids, we adopt
to [18]):

confinement force), advection, diffusion, and projecti
for the vorticity field for the later use of grid division.
t the following model to calculate the velocity field (ref

ion.

fers

where and is the ve
the time step in fine grid (h
term in the right hand side o
high computation cost, this
will not lead to the unstable

locity in coarse grid and fine grid respectively, deno
here we set 0.25 ). As there is only one advect
of equation (3) and there is no projection term which ne
s method is efficient. Moreover, experiments show tha
e phenomenon with our method.

(3)

otes
tion
eeds
at it

3.3 Vorticity-Based Gr rid Division Scheme

If we adopt the global grid
way, the computation will i
detail, we proposed a new g
the grids with rich details a
of fine grid is two times of t

division scheme, i.e. treat all the coarse grids in the sa
increase sharply. Considering that not all grids contain r
grid division scheme based on vorticity field. It can iden
adaptively, and divide them into fine grids. The resolut
the coarse one per dimension.

ame
rich
ntify
tion

(a)
Fig. 1. The results of grid divi
they represent a slice of the si
need division. In figure (b), th
obstacle are divided.

(b)
ision. The coarse grid resolution of both (a) and (b) is 16×16×
imulation at some time. The pink part represents the grids wh
he blue part represents the obstacle. The green grids around

×16,
hich
d the

Vorticity can be regarde
ticular axis, which represen
quantity to determine wheth
get vorticity field value thro

ed as a phenomenon of local smoke rotates around a p
nts the richness of the smoke details. Therefore we use
her a coarse grid is needed to be divided into fine one.
ough each coarse grid's curl of velocity field as follows:

par-
this
We
:

us of each coarse grid's vorticity field value | | with
| . If | || | , then this coarse grid need to be divi

(4)

Then, compare the modulu
modulus of threshold |

the
ided