I have had an experience that invisible objects' shadows appear.

 I'm not sure that this phenomenon is worth to report on this news group.
 Because I don't know if this phenomenon had been reported or described in
the document of POV-ray language very well.
 But I try to report this hoping this report is helpful.
( And permit me to write in poor English and correct wrong expression if I
wrote.)

 I tried to make a shape by subtracting some objects from a base object. And
I have had some unexpected results. The expected result is Fig.4.
 I guess the problem is the invisible objects' shadows written in chapter 3
and Fig.3 below. I attached the scene file. Please see it if you would like
to know about the scene file in detail.

1. Result of coincident surfaces
     I rendered the scene file I made. Then the result was as shown Fig.1.
     This result commonly happens because the scene file included some
coincident surfaces.
     I used two casts shown below to cut (subtract) base object.


Fig.1

Cast 1    Cast2



2. Result of coincident surface
      I moved the Cast2 little bit. Then the result altered as below.
     Some of the partial surface because of coincident surfaces was reduced.
But something is wrong inside the circle. I cannot see the surface made by
Cast1. Is this also some problem concerning to next chapter?

Fig.2

3. The shadow of invisible objects
     Next, I moved the Cast1 same distance as Cast2. Then the strange shadow
appeared. According to the shape of this shadow, this problem have something
to do with number of times of intersection. (e.g. intersection time is odd
number, then rendered expectedly.)

Fig.3

4. Expected result
     Finally I moved the Cast1 to opposite direction. Then I could get
expected result.

Fig.4



That's all. Bye (^_^)/

Best regards

Masanori Imazu

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Attachments:
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It is unlikely that you get (much) other feedback not because nobody 
knows/wants to help/deal with this problem, but
1. Please read <http://www.povray.org/groups.html> why this is the wrong
group.
2. Please don't post graphics etc in non-binary newgroups as there are
people here with slow connections (paid per minute).
3. Also note HTML posts are likely ignored by all those here in the
newsgroup that don't use HTML newsreaders. Posting in plain text is increase
your chance to get an answer by several orders of magnitude! :-)

If you have problems with a scene (or questions why a specifc workaround
works/does not work) you might consider the general or newusers (even if you
aren't a new user) groups to post a question/note like this.


     Thorsten

PS: Don't worry, if you post the message (again) as plain text in
povray.general (graphics in a povray.binaries.images and refer to them) you
will find a lot of help from the users around here.

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Thank you for your kind advice. I changed the message to plain text with
some modification and further comments and post it again.

 I have had an experience that invisible objects' shadows appeared.

 I'm not sure that this phenomenon is worth to report on this news
roup.( But I think the phenomenon I experienced is classified into a kind of
bug.)
 Because I don't know if this phenomenon had been already reported or is
described in the document of POV-ray language very well.( Maybe NO.)
 But I try to report this hoping this report is helpful.
( And permit me to write in poor English and correct wrong expression I
wrote for my learning English. )

 Unexpected shadow appeared although I avoided coincident surface by moving
objects. It looked like occurring on coincident surface between imaginary
disc which has circumference on a point of lathe object and surface of box
 or other ) objects. And this phenomenon looks like concerning to what (even
or odd) times objects intersect at the same area.


 Detail of my experience is as follows;

( I attached the scene file. If you render it, you can see the shadow of
invisible objects. Please see it if you would like to know about this in
detail.)

 I tried to make a shape by subtracting two objects from a base object.
 The base object contains a big box. One of two objects for subtracting is a
lathe object. And the other is an union object just like the cross consists
of two long boxes.

 At first there were coincident surfaces between the base object and the
cross object. So I modified the scene file.

 I moved the cross object first because the coincident surfaces were only on
the cross object. Then some unexpected parts which looked like scattered pin
holes disappeared. But unexpected area still remained in the lathe object
which is subtracted.

 So I moved the lathe object the same distance as the cross object had been
moved. Then the strange shadow appeared.
 The object's shape was good. But there were some unexpected shadow on the
object.


That's all. Bye (^_^)/

Best regards
 Masanori Imazu

P.S. Do I have anything to do against the already posted message(HTML) in
order to save disc space on this server?

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I forgot writing pertinent information.

POV version :
    3.1a.watcom.win32[Pentium II optimized]
    and
    3.02.watcom.win32[Pentium optimized] ( the results are almost the same
as Version 3.1a )

Machine :
    IBM Aptiva
    CPU : Pentium MMX 233MHz
    Memory : 64 MB

OS    : Windows95

Best regards
 Masanori Imazu

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I think you're still dealing with some form of the coincident surface
problem.  In the Object_A declaration, try changing the line
      object { Cast2 translate -0.001*y }
into
      object { Cast2 translate -0.0011*y }

This fixed the problem on my system.  ;-)

-Nathan

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