On 11/12/24 03:17, William F Pokorny wrote:
> Thanks for the references. IIRC shadertoy has a distance method to draw 
> the outline of cells, but I don't recalled the particulars at the 
> moment. I have ideas for how to do it in C++, but I also wonder if in 
> yuqk it cannot already 'mostly' be done. Stuff like this why I added the 
> ip_raw_return as a yuqk crackle option. Maybe I'll take a 'crack' at it 
> in a bit.

I didn't spend much time on it, but the top of the attached image shows 
outlines as a pigment just slightly red (negative) by allowing raw value 
returns after changing ip_form to: 'ip_form <-0.1,0.08,0> - the default 
is <-1,1,0>.

The bottom of the image is an isosurface where a cylindrical shell is 
intersected with a similar crackle pattern in space. No attempt wrap the 
cylinder - just punching out a thin part of the crackle cell outlines.

The isosurface functions are:

// yuqk required
#declare Fn00 = function (x,y,z) {
     f_planar(f_cylinder(x,y,z,0.9),0.01,1)
}
#declare FnCrk = function {
     pattern {
         crackle
         ip_form <-0.1,0.097,0>
         ip_strength <0.25,0.25,0.25>
         ip_raw_return
         raw_wave
         translate <0,0,0.25>
         scale 1/5
     }
}
#declare Fn01 = function (x,y,z) { max(Fn00(x,y,z),FnCrk(x,y,z)) }

Yes, The outline / cell-walls vary some due differences in gradients - 
but more due how the slices catch the cell wall. For practical purposes, 
expect an approach like this often OK for cell outlines.

Bill P.

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