"Yadgar" <j.b### [at] ndhnet> wrote in message
news:3B2200DF.B10D830A@ndh.net...
>
> That was a problem I encountered before; originally, the centers of the
> cylindrical lamp bodies were placed at a radius of 5 from the center of
the
> whole cylindrical habitation module, while the inner surface of the round
wall
> also was at 5 (i. e. a cylinder with radius 5 cut from an originally 5.1
> cylinder - the remaining wall is 0.1 units thick). But then the image got
> completely messed up with bizarre coincident surfaces effects, so then I
placed
> the lamp bodies instead at 4.99.

Although probably not a factor here you need to be aware that small numbers,
such as those of thousandths or less, can be trouble for POV-Ray if it
concerns an objects size.  Sphere for example will degrade at a mere <0.02,
box next, and eventually cylinder.  The cone primitive proves to be sturdy
at most any scale.
This doesn't apply to translated surfaces, lights, far as I know anyway.
Just thought I should mention it since you are working with fairly small
scales already.

> You should know that the from whole lamp body a large box is subtracted to
> prevent it from peeking out of the outer side of the round wall (its
radius is
> 0.15, while the wall is only 0.1 thick). As I did that only after I added
caps
> and belts, I assigned no texture to the box... could THAT be the reason??

If a CSG difference is used then yes, it matters that the cutaway object
isn't textured after the previous object to be cut is textured.  If
clipped_by is used it wouldn't matter.  An untextured object is blank, or
rather appears opaque black, so to leave it textureless (i.e. without the
parent CSG object texture) is sure to be conspicious.

> I just looked up the code again and found that the box goes from z=0.01 to
> z=0.2... with the center of this slightly-more-than-half-cylinder at 4.99,
its
> cut side is still in direct contact with the wall. Now I changed the z
value of
>
> the box' lower left front corner to 0.001 and started again...

Check into using clipped_by I think might be the answer if you're using
difference now.
This rendering still looks a lot like coincident surfaces but have you tried
using more sources for a higher sampling in those area lights? 2x4 or 2x8
might be needed, it could be that 1x4 causing the problem in part or whole.

Bob H.

Post a reply to this message