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Bruce Feist · Guest

I've recently started playing with Java3d; I teach Java in HS and am
eventually hoping to incorporate some game design into my course.
Anyway, I'm running into a bit of a problem which I haven't been able to
solve using the Sun tutorial or the API documentation.

I'm displaying a shape called a Mobius strip, and I want to display it
in such a way that you can tell which side you're looking at
(technically it has just one side, but the concept remains). If you
don't know what a Mobius strip is, that probably won't matter for your
answer to the problem -- if you're curious, think of it as a long strip
of paper in a loop, with a twist in it so that what was the 'front'
turns into the 'back'.

One possibility would be to display a series of parallel arrows pointing
across the strip, something like this:

----------------------------
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
----------------------------

The arrows would point up on one side, and down on the other. Another
possibility would be to use two colors to draw it, one for the top and
the other for the bottom. I don't much care which; they all boil down
to the same problem, which I can't figure out how to solve: how do I get
the two sides to look different? Can I have two textures, one which is
visible from the front and the other from the back? Must I resort to
havng two actual surfaces at a small displacement from each other?
(This one would actually be pretty hard to get working for a Mobius
strip, I think -- I haven't thought it through completely.)

Any suggestions would be welcome. Please be gentle; I'm new to this!

Thanks,
Bruce Feist

sanbikinoraion · Guest

A mobius strip would, ofc, be represented as a triangle strip in
java3d. A single triangle strip would of course only fill on one side
(and java3d will handily let you pick which side!) so my advice would
be to make a triangle strip, clone it, and texture it appropriately,
then take the cloned triangle strip, flip the visible surface, and
texture it in the other manner. Of course, because of the half twist,
the textures will appear to suddenly flip over where the triangle strip
starts and ends.

My suggestion, therefore, would be to colour shade the individual
vertices of the triangle strip starting from red and running halfway
through the spectrum. The backface triangle strip should do the same,
running from halfway through the spectrum to the end of the spectrum (a
very reddish magenta).

Hope that helps!

sanbikinoraion

Bruce Feist wrote:

Bruce Feist · Guest

sanbikinoraion wrote:

sanbikinoraion · Guest

ofc = of course, ofc :P