Ken wrote:

>  In the sample below we have an example of degenerate triangles. The
> indented triangles are those that Pov reports as being degenerate.
> When rendered as a union the degenerate warnings appear. When commented
> out those warnings disappear. When rendered as a mesh however Pov fails
> to report them as being degenerate. This has been true since the mesh
> wrapper was added in Pov v3.0x. Why are they not being reported as
> degenerate triangles when used in a mesh ?
>
> I have asked this before and have never received a response. Hopefully
> someone has an idea now that I have provided an example to evaluate the
> discrepancy with.
>
> //union{
> mesh{
>    triangle{<0.1173,0.4003,0.0>,<0.0,0.4,0.0>,<0.0,0.4,0.0>}
> triangle{<0.0,0.4003,-0.1173>,<0.1173,0.4003,0.0>,<0.0,0.4,0.0>}
>    triangle{<0.0,0.4003,-0.1173>,<0.0,0.4,0.0>,<0.0,0.4,0.0>}
> triangle{<-0.1173,0.4003,0.0>,<0.0,0.4003,-0.1173>,<0.0,0.4,0.0>}
>    triangle{<-0.1173,0.4003,0.0>,<0.0,0.4,0.0>,<0.0,0.4,0.0>}
> triangle{<0.0,0.4003,0.1173>,<-0.1173,0.4003,0.0>,<0.0,0.4,0.0>}
>    triangle{<0.0,0.4003,0.1173>,<0.0,0.4,0.0>,<0.0,0.4,0.0>}
> triangle{<0.1173,0.4003,0.0>,<0.0,0.4003,0.1173>,<0.0,0.4,0.0>}
> }
>

Well, POV-Ray reports them as being degenerate because they are :-)

I'm not sure, but I just encountered this recently when I was doing some
macro work just the other day. Guess I have to look into the code and see.

My guess at the time was that the mesh was doing some conversions of
melding all the identical points whereas the union was keeping things as
separate triangles, and in the mesh process things were skipping a check
step that the union triangles were subject to. But as I said, this is just
a guess and I have to look at the code to be sure.



--
"My new computer's got the clocks, it rocks
But it was obsolete before I opened the box" - W.A.Y.

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