On 3/25/20 8:05 AM, William F Pokorny wrote:
> On 3/25/20 5:52 AM, Jim Holsenback wrote:
...
> 
> Anyway, I've promised to do some other stuff first thing this morning. 
> I'll come back to this thread later.
> 

OK.

---
Modifiers are not generally passed from nested objects to a csg 
resultant involving those objects - excepting with unions and there 
excepting unions using 'split_union off'. This is true for:


Keywords:
---------
no_image
no_reflection
no_shadow
no_radiosity
double_illuminate
hollow

Modifier blocks:
----------------
photons {}
radiosity {}


The following are OK if applied to csg components:

Keywords:
-----------------------------------------
all transforms
inverse
bounded_by
clipped_by
cutaway_textures
hierarchy
sturm


------------------------
And then we have interior{} and subsurface{} object/finish block modifiers.

Interiors get attached to the objects where the interior is defined. The 
subsurface{} ended up as part of the finish{} block instead of being 
like other block modifiers - anyone know why? In any case that is part 
of the texture attached to the object. What this means is these two 
object modifiers blocks should propagate with the objects surfaces 
through csg. However.

With interior{} the behavior even propagated will be iffy for overlapped 
interiors/no-interior surfaces. There is basically an interior stack and 
if the interiors are seen out of order or due a difference say by only 
entering or exiting surface we'll get the wrong interior treatments, 
media artifacts and the like. Things might work OK, might not. It's 
complicated and a situation true propagation through csg or not.

With subsurface{} things might work better just thinking about it - 
perhaps why the block is part of finish{}? I tested a difference both 
with and without cutaway_textures and functionally I see correct 
behavior without the cutaway_texture and 'sort of' the right result with 
cutaway_texture. In the later case, the subsurface result doesn't look 
to me to be quite right. With cutaway_textures on, if I add a finish 
block to the sphere cutting into the candle, the region turns white with 
no warnings whatever that's about. As just prior, but adding a candle 
matched pigment I get a result matching the original cutaway_textures 
result. To me the color in the divot is more like what it might be if 
the original candle was being used for the subsurface calculations and 
not the candle with the divot and the thin parts at the lip are pretty 
dark - are subsurface rays jumping through the the thin parts?

So... Suppose with interior{} and subsurface{} I'd summarize as:

-----------
The interior{} and subsurface{}(1) object and finish modifier block 
results, respectively, vary where definitions are part of components 
making up any given csg.


The disclaimer here is I've not created but a half dozen test cases to 
verify behavior. With the no_* and hollow keywords confident without 
testing. Anyway, I think I have the behaviors through csg mostly right...

Bill P.

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