I have managed to manually specify texture co-ordinates for a planar 
projection texture map - it turned out to be a lot easier than I thought.  I 
now have to implement cylindrical texture maps.  I am loading low2 objects 
and the help for cylindrical tmaps is:

The image is wrapped cylindrically around the major axis. r maps to 
longitude (angle around the major axis).

I know the major axis and I know the bounding box of the object, can anybody 
point me in the right direction for applying these co-ordinates?  I then 
have to implement spherical but this will be easy if I know how to do the 
cylindrical.

Thanks,
Allan

Allan Bruce wrote:
> The image is wrapped cylindrically around the major axis. r maps to 
> longitude (angle around the major axis).

Easiest, sorta backwards, way to do it, would probably be to rotate the
object to orient the object-space coordinatesystem according to the 
cylindrical projection. Then you could convert all xyz-vertex
coordinates to cylindrical coordinates:

http://mathworld.wolfram.com/CylindricalCoordinates.html

- and rescale to the interval [0..1].

The rotation is probably done most easily using a basis-shift (consult
your linear-algebra book), but you need to decide on a default
orientation of the cylindrical projection (like, where does your image
split, what is "up" etc.)

> I know the major axis and I know the bounding box of the object, can 
> anybody point me in the right direction for applying these 
> co-ordinates?  I then have to implement spherical but this will be 
> easy if I know how to do the cylindrical.

- same procedure (as last year, ms. sofie), only use
http://mathworld.wolfram.com/SphericalCoordinates.html

This will get you the basic projections - the rest is tweaking ;)


Hope this helps,
\\Mikkel Gjoel