Hi All, I've had a look through the mail archives, and I don't think this has been asked before, so I was hoping someone might be able give some guidence to me on a question I'm bashing my head with at the moment. Its not strictly an osg question - though I am using osg to try and solve it.
Question ====== I have a general triangle in 3D space, known coordinates, with known S,T texture coordinates. Knowing only this information, is it possible to calculate the size of the texture? Background ======== The background to this problem is that I have an object with texture coordinates, that has applied a texture. I now wish to apply a new texture to this object where I know the size that this texture is mean't to represent in the 3D space. Thus I believe I need to scale the texture coordinates on the object such that the size of the new texture is correctly represented relative to the object. [Brief asside - I suspect that there might be a way to do this other than altering all the texture coordinates, perhaps a scale measure on a texture object but I haven't delved deep enough into osg::Texture2D to know.] In order to scale the texture coordinates I need to know the size that the original texture represented relative to the object/universe it was in. Each geometry could have its own texture, therefore I'm at the geometry level, and I have the triangle with the largest variation in the S,T domain. I can transform this triangle to a cordinate system that is co-planar with the triangle, where one edge forms the first of a pair of orthogonal basis vectors in the triangle plane (e1,e2), and hence I can represent my triangle in this space. The S,T domain is coplanar for my requirements, and with a shift of origin, (0,0) in the S,T domain maps to (0,0) in the e1,e2 domain. So I get to a point where I have the two sets of orthogonal axis in the same triangle plane, where a rotation of the e1,e2 axis would align them to the U,V axis. However, my next step is not clear. Can any one assist please. I may be barking up the wrong tree here, and if so, please accept my apologee. Thanks for any help Neil Hughes. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
