"Jim Hart" <nomail@nomail> wrote:
> Hi. I am having a problem figuring out why POV-Ray is not allowing me to overlap
> several objects that have emission media interiors. I have attempted to vary
> both pigment and finish, but it seems that the resulting images show the
> surfaces of the objects when they intermix with the interior media of another
> (an effect I do NOT want).

Yes, I've seen that effect too some time ago, and actually gave up trying to
work around it because it wasn't too prominent in the particular scene I was
working on.

My current guess is that this could be a problem of sample distribution within
an object. Ideally, the distribution should be something like this ("|"
denoting the object's surface, and "*" denoting a sample being taken; note that
I'm aware that adaptive sampling is a bit more complicated):

   |--*----*----*----*----*--|

or:

   |*----*----*----*----*----|

I.e. the whole distance should be subdivided into as many subsections of equal
size as there are samples, and one sample taken per such subsection. However,
maybe the samples are instead distributed such that the first sample is taken
right at the beginning of the whole distance, and the last one at the very end,
i.e.:

   |*-----*-----*-----*-----*|

If this is the case, it would be no surprise to see artifacts at the interface
between two objects, even if they have the same interior properties:

   |*-----*-----*-----*-----*|*-----*-----*-----*|

Here, the density function value at the interface between the objects receives
twice as much weight as any other.

So that's what I guess is happening, although I haven't been able to find any
confirmation of this in the code so far.

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