On Thu, 09 Dec 1999 13:12:13 -0500, Greg M. Johnson wrote:

>For example, if I want the noise3d function to be terminated above y=0, there are a
>bunch of ways to do this with CSG. All of these would be a harsh cut.   I am
>betting there is a way to make a very smooth termination of the function by playing
>with the threshold values.

Probably not.  what you need to do is add on some function that stays constant 
below y ~= 10, then drops smoothly as you approach y=10.  I'm not sure there 
are any non-piecewise functions that do that, but you might be able to 
approximate it with the right sort of asymptotic function.  If you're using
the preliminary 3.1g superpatch, you'll find that there's a ?: operator in 
there that might make piecewise functions possible, but that version has 
other problems you might wish to avoid.

>I guess that something like,
>isosurface{
>               fucntion {noise3d( x, y+9.5, z)}
>               threshold 10
>               }
>might do it, but I'm not sure.

Almost definitely not.  The function you've specified there is just the regular 
noise3d function translated downward 9.5 units, but the threshold of 10 will
ensure that you only see a solid block, since the noise3d function never goes 
above ten (it rarely goes above one.)  (I see you mistyped 'function' the
same way I did. :) )

>Q2:  So what are the operational thingies that work with the isosurface?
>    & is and or intersection,

There's also |, which is merge.  I'm not sure what else there is, believe it
or not.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

Post a reply to this message