Rob Nugent wrote:
>
> Is this not occuring because culling is performed by Java3D
> using a *real* normal from the triangular surface, i.e. that
> calculated from the cross-product of the side vectors ot
> the triangle.
Well I suspect that is the case but can find no documentation to support
or deny it. Again, magic behaviour.
The *really* odd thing about it was that if I did that and then applied
emissive colour to the object it would render it like it was
semi-transparent. ie I could see the objects "encapsulated" by the
object in question but you would still see the "back" face now rendered
in what appears to be a transparency style. No other color parts from
the Material would effect it, just emissive colour. This part, I'm
willing to believe is a video card driver issue, but the fundamentals of
implied ccw vertex ordering seem very odd to me.
> I always assumed that the normals that you supply are solely
> for lighting purposes, and indeed are not necessarily perpendicular
> to a triangle.
The problem then is dealing with incoming data sources that define thier
data as clockwise points. A lot of the time you don't even know so a
file loader just blindly applies the data to j3d and then things just
don't show on screen. That is, it is almost impossible to know whether
you have to unwind all the coordinates given to you to make them
visible. Also, for index data types and fans, It would be a bit of a job
to do it too. Lots of data shuffling and correspondingly huge amounts of
memory consumed.
(Atypically, the VRML spec says clockwise is the default and you have to
set a flag to tell it the reverse, so at least you have a chance here).
--
Justin Couch http://www.vlc.com.au/~justin/
Freelance Java Consultant http://www.yumetech.com/
Author, Java 3D FAQ Maintainer http://www.j3d.org/
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"Humanism is dead. Animals think, feel; so do machines now.
Neither man nor woman is the measure of all things. Every organism
processes data according to its domain, its environment; you, with
all your brains, would be useless in a mouse's universe..."
- Greg Bear, Slant
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