View Full Version : noise function..

 Norb03 March 2003, 10:01 AMok guys, what am I doing wrong here, i'm putting this into the alpha gain.. file1.alphaGain = noise (0.04,0.1); so I want it to vary between 0.04 and 0.1 but when I apply it, it gives it a value of -0.306, what's up with that?
alexx
03 March 2003, 10:21 AM
i think noise returns the value from a static noise field (like a 3d texture).. for the same input you always geht the same output..

what you are looking for is
rand(0.04, 0.1)
i think

cheers

alexx

dwalden74
03 March 2003, 10:43 AM
so I want it to vary between 0.04 and 0.1 but when I apply it, it gives it a value of -0.306,

Noise returns a value from -1 to 1. IŽd recommend checking the expressions docs when youŽre not sure about these things.

:beer:
David

mark_wilkins
03 March 2003, 09:26 PM
Just remember, Perlin noise (as represented in the noise function) and "white" noise, (also known as broad-spectrum noise, represented in the rand function) are NOT the same.

Perlin noise is pretty much low-pass-filtered white noise.

-- Mark

skigil
03 March 2003, 04:57 AM
i used the noise function once in an expression. i used it as a way to get around animating an always moving tail on a ghostly figure. i loved it :)

-skigil

Norb
03 March 2003, 06:39 AM
well, I've kindof gotten it working now, I wanted to use the noise fucntion to give a more smooth interpolation between values rather than a rand function, because this is controlling a glow, and I wanted it to oscillate rather than flicker....but I figure it might be easier to key it and then set it to post infinity.... Thanks for the help guys!

Duncan
03 March 2003, 06:35 PM
If you want some continuity between frames( this is usually desirable ) then use noise. The inputs to noise are coordinates, not ranges, so you need to remap the output of noise ( -1 to 1 ) to your desired range. To animate noise you pass in a changing value into the input coordinates(like walking along a texture).

float \$speed = 1.0; // speed of flickering
float \$minValue = 0.04;
float \$maxValue = 0.1;

file1.alphaGain = (noise( \$speed * time )+1.0)*0.5 * (\$maxValue-\$minValue) + \$minValue;

Note that this is only using a one dimensional noise. One can use two or three arguments to the noise function as well for 2 and 3D noises. Typically we use spacial values (x,y,z) or (u,v) as inputs to noises, but one can be creative and use time or other values that vary.

Duncan

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