"Josh" <nomail@nomail> wrote:

> from the Inigo Quilez examples you posted earlier. I'm trying to figure out how
> to union/merge boxes together and then round them all together. The math is
> confusing me. I took enough calculus years ago I should be able to figure it
> out, lol. His SDF functions are very similar to isosurface functions, yet they
> are different enough I can't get them to match. In his SDF functions he is able
> to simply subtract r from the function to round a shape, but I can't get the
> isosurface functions to match that.

Ah, yes.
That's because POV-Ray doesn't have vector functions, which makes everything a
giant PITA.
I had to follow along with his video
https://www.youtube.com/watch?v=62-pRVZuS5c
to figure out how to do it, but it works very nicely   :)


#declare Rx = 2;
#declare Ry = 3;
#declare Rz = 1;

#declare Q = function {sqrt( pow(max(abs(x)-Rx,0),2) + pow(max(abs(y)-Ry,0),2) +
pow(max(abs(z)-Rz,0),2) )}
#declare QX = function (x) {max(abs(x)-Rx, 0)}
#declare QY = function (x) {max(abs(y)-Ry, 0)}
#declare QZ = function (x) {max(abs(z)-Rz, 0)}
#declare D = function {Q (x,y,z) + min(max( QX(x), max(QY(y), QZ(z)) ), 0)}

Now here's the tricky part, which I can't really explain very well ATM.
You either need to subtract an amount equal to the radiusing of the corners from
the function D, or you need to use that non-zero value as the isosurface
threshold.  Otherwise you get no visible isosurface.
Which can drive you insane trying to debug the equations, the code, etc.

If you want a box of a specific size, with a specific radiusing of the edges and
corners, I think the way to do that is #declare a Radius value and subtract that
from Rx, Ry, and Rz, so that when you bump out the function by the radiusing
value - you're back at the original parameters.

Play with what I have right now and you'll see what I mean.
The isosurface gradient is only about 1.3.

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