home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Inside Multimedia 1995 December
/
IMM1295.ISO
/
share
/
grafik
/
povhelp
/
turblnce.hlp
< prev
next >
Wrap
Text File
|
1994-07-07
|
2KB
|
35 lines
The keyword 'turbulence' followed by a float or vector may be used to
stir up the color pattern. Typical values range from the default 0.0 which
is no turbulence to 1.0 which is very turbulent. If a vector is specified
then different amounts of turbulence is applied in the x, y and z direc-
tions. For example 'turbulence <1.0, 0.6, 0.1>' has much turbulence in the
x direction, a moderate amount in the y direction and a small amount in the
z direction.
Turbulence uses a noise function called DNoise. This is sort of like
noise used in the bozo pattern except that instead of giving a single value
it gives a direction. You can think of it as the direction that the wind is
blowing at that spot.
Turbulence which uses DNoise to push a point around a few times. We lo-
cate the point we want to color (P), then push it around a bit using turbu-
lence to get to a final point (Q) then look up the color of point Q in our
ordinary boring textures. That's the color that's used for the point P. It
in effect says 'Don't give me the color at this spot... take a few random
steps in a different direction and give me that color. Each step is typi-
cally half as long as the one before. For example:
P ------------------------->
First Move /
/
/
/Second
/ Move
/
______/
\
\
Q - Final point.
The magnitude of these steps is controlled by the turbulence value.