On 12/22/2017 10:21 AM, Bald Eagle wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
> 
>> You've got it. That is exactly what I'm doing, but where that sort of
>> image has been translated into a plane of a df3 density file.
> 
> So, just a single layer of voxels in that unit cube - in the x-y plane.
> 

For the shape yes. I also buffer on all sides with 5 voxels at 0 to 
avoid the density_files edge effects during interpolation.

> 
>> #declare FnctTheDF3 = function {
>>       pattern{density_file df3 "the.df3" interpolate 3 // 1 if no patch
>>       translate -0.5
>>       scale 1+(10/800)               // lose df3 side buffer padding.
>>       translate 0.5
> 
> I'm assuming the unit cube extends from <0, 0, 0> to <1, 1, 1>
> so you translate -0.5 to center on the origin, scale, then shift back.
> 

Yes, and I should correct the line:

     scale 1+(10/800)

which worked for what I was doing, but it was an approximation. A better 
scale up - to push the buffer voxels outside the unit square - would be 
oriented only in x and y and be adjust for the df3 dimensions.

...
#declare VarPadding = 5;
#declare PadScaleXY =
     <Df3Range.x/(Df3Range.x-2*VarPadding),
      Df3Range.y/(Df3Range.y-2*VarPadding),1.0>;
...
     translate -0.5
     scale PadScaleXY
     translate 0.5
...

> 
>>       scale NrmScale*<0,0,3>+<1,1,0> // to thin plane, z 3x thicken
>>       translate <0,0,0.5>            // Set box width to 1.0.
> 
> Then you shift the df3 "back" to get the front layer at z=0

Yes and then the 0.5 offset to set the half width (radius for other map 
types) during the warp - this last part has to do with how the warp{} 
mapping works. The deep pink isosurface shape in the attached image more 
or less shows the shape as it would exist at z=0.5 inside the unit cube 
after that last translate.

> 
>>       warp{cubic}                    // Wrap pattern around origin.
>>       warp{turbulence 0.04 octaves 5 omega 0.4 lambda 5} }
>> }
> 
> I suppose it ought to be simple enough to write a macro that assembles such a
> map from a square, or add an internal function that does the same.
> 
> 

Yes, I think many ways possible to create the df3 plane(1) including 
variations of the cubicMap.pov code attached earlier to this thread.

Your news post timing was good because I also need to make a correction 
to the code snippet I posted.

The z passed to the pattern based function needs to be flipped to match 
the in built in uv_maping for a box object and the warp{cubic} of an 
image_map applied to box. These two more routine results being the left 
and right white textured boxes in the attached image.

In other words where I had:

#declare Fn00 = function (x,y,z) { 0.025-(FnctTheDF3(x,y,z)) }

it needs to be:

#declare Fn00 = function (x,y,z) { 0.025-(FnctTheDF3(x,y,-z)) }

for the resultant isosurface (center box in the image) to match the two 
other cubic maps. Off the top of my head, I'm unsure why the inversion 
in z when used in the isosurface... I didn't notice the z-flip until I 
tried my first non-symmetric map earlier today.

Bill P.

(1) - It need not be just one plane. We could create boxes within boxes 
for example as one media/isosurface at the cost of the df3 getting 
deeper/larger to do it.

Post a reply to this message

Attachments:
Download 'isoboxcubicmap.jpg' (212 KB)

Preview of image 'isoboxcubicmap.jpg'