"Chris B" <nom### [at] nomailcom> wrote:
> "Kenneth" <kdw### [at] earthlinknet> wrote in message

> > Thinking about it logically, all the colors *should*
> > be the originals, not averaged ones;
>
> I would argue that the original colors *are* shown, except where two objects
> occupy the same physical space, which is something that doesn't typically
> occur in RL solids. So I guess POV-Ray is forced to do something a bit
> 'unrealistic' to represent an unrealistic RL condition.  If you add a real
> spark plug into a cylinder block you'd normally have to cut a hole in the
> cylinder block first, unless your tool of choice is a sledgehammer (a most
> versatile tool).

Ah yes, that bit of logic escaped me while thinking about this. :-(  You're
absolutely right, a 'simple' cutaway after-the-fact isn't a real-world
situation.
>

>
> One approach I've found successful is to adopt a cookie_cutter type of
> concept, where I define a cutting object at the top of the scene file...

A very interesting idea, one I wouldn't have thought of. I'll have to try that.

In thinking further about the 'averaged' cutaway pigments (as happens now), I
do see the difficulty that POV has in determining *which* surface to choose the
color from, when multiple nested objects are cut across. It seems to me that a
way around this limitation would be: whatever individual object 'volume' the
camera ray hits at the cutaway surface, that's the color that should be
returned. The color of the 'innermost' of any nested objects there, if that
makes any sense. (And I may not be thinking *this* idea through to its logical
core.) But apparently, POV's ray-tracing process currently doesn't work on
'mathematically-created' objects this way (like a box or cylinder, etc.) I.e.,
there's no real internal 'structure' to such objects that a ray can look at at
a particular point in space. That's my simplistic way of thinking about it,
anyway! Yet, a ray *must* be seeing that point in space, in order to do simple
CSG differencing, for example.  So I'm baffled about the cause (or reasoning
behind) the 'averaged' pigments.

KW

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