You're right. of course.  I wasn't implying that it was wrong, just that
it "appears" backwards compared to other types of scaling.  For example,
if I wanted a large bump scale on a normal, I would increase it, but
with noise3d, I would use a smaller number.

As, I mentioned, I don't have a lot of experience with isosurfaces, so I
don't think in terms of how the function will be satisfied; I'm relating
it to similar POV-Ray statements.

Mike Wilson

Chris Huff wrote:
> 
> In article <3875FB3E.46031B75@iastate.edu>, maw### [at] isunetnet wrote:
> 
> > I may be compeletely wrong, because I don't have a lot of experience
> > with isosurfaces, but I did run into something similar.  It seems to me
> > that the isosurface code works "backwards" from normal POV-Ray
> > nomenclature. i.e. something like isosurface{y-noise3d(x,y,z)} actually
> > adds the height of the noise to the plane whereas
> > isosurface{y+noise3d(x,y,z)} subtracts the noise from the surface.
> 
> That isn't backwards at all. The isosurface of the function y-1 will
> consist of all points where y-1 is the threshold value. Increasing the
> amount subtracted from the y coordinate means y has to be higher to
> result in the same value. When noise3d equals 1, y has to equal 1. When
> it is added instead, y has to equal -1 to get the same result.
> 
> > Likewise it seems that increasing the x,y,and z values makes for smaller
> > noise features. e.g. noise3d(x*20,y*20,z*20) makes finer detail than
> > noise3d(x*3,y*3,z*3).
> 
> Again, this is not backwards. If you multiply x by 2, than the result of
> that expression(2*x) will be a certain value at half the distance it
> would be without the multiplication. The result is compressing the
> coordinates into a smaller space, scaling down.
> If x is 3, 2*x will be 6, and the features that would have been at x=6
> will be at x=3 when 2*x is used.
> 
> --
> Chris Huff
> e-mail: chr### [at] yahoocom
> Web page: http://chrishuff.dhs.org/

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