"Carl" <car### [at] semisouthcom> wrote:
> "Mike Sobers" <sob### [at] mindspringcom> wrote:
> > An alternate solution to those already posted is to try to reproduce the
> > process used for the original TRON images.  The gridlines are 2D objects
> > pasted onto the image plane (i.e. your computer screen), not onto the floor
> > plane.
>
> If that's correct why are there shadows on the grid lines in TRON?
>
> http://digitalstratum.com/images/tron/screenshots/hover_5.png
>
> They look to be 2D objects pasted on the floor plane to me.

That's because the shadow is pasted on _top_ of the grid lines.  That's what
z-buffering is all about! See http://en.wikipedia.org/wiki/Z-buffering

>
> Thanks for all the work guys I still need to do my part and try to digest
> everyone elses posted solutions but so far I don't think anyone has
> actually reproduced the process used for the original TRON images.
> Considering how "primitive" the raytracing software MAGI used back then
> must have been by today's standard it amazes me sometimes just how hard it
> is to copy what they did with today's software.

I may be wrong, but I doubt that in '82 they were using raytracing for these
CGI animations (hard to believe I was only 7 then ;) ).  That's why it's
hard to reproduce the effects using a raytracer (same reason why games
don't use raytracing - it's too slow).  The process they were probably
using is effectively what OpenGL and Direct3D do today. It's equivalent to
cutting out little pieces of colored paper and arranging them on your desk,
then snapping a picture.  That's why the perspective (i.e. disappearing grid
lines) doesn't have to match reality - the shape you cut out for the little
pieces is totally up to you, but matching a real perspective view helps
improve the image.  That's why I think the original gridlines were not
produced by a raytracing engine (evidenced by the fact that they don't get
infinitly thin as they approach the horizon) but instead by the process I
was trying to describe above.  That's why I say the TRON gridlines aren't
_on_ the floor.  They tried to make them _look_ like they're on the floor,
and they got pretty close, but not as close as actually putting them on the
floor like POVRay does.

Mike

P.S. - great work, it's got a lot of us really thinking!  I think I may have
to go rent TRON again.

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