Hi Neil I would say no, not from that info, ST simply map to the texture 0 to 1 no matter the size of the texture in pixels etc.
you could get the state set of the geode the texture is being to and get the texture /image size in pixels but this would still not have enough information as what is the real-world size of the texture, you only have pixel size, what does one pixel represent ? 1cm, 1m 10m, 100m etc Multigen Creature actually has a solution for you, all textures applied in Creator to a model have an *.ATTR file created ( myTexture.jpg.attr ) that contains a field to set the textures real world size among other useful information. I'm not sure if OSG reads these, most programs ignored this field but used the others like filters to apply to mipmap etc . In my old GIS product SiteBuilder3D we made a lot of use of this real world size to map textures to extruded shape files etc to ensure building sides, bricks, walls, windows mapped to correct actually size. But this relied on the real-world size being set correctly in the Attr file If you don't know the Real-world size that the texture covers, what each pixel represent then you cannot really achieve what you're after, ____________________________________________________________________________ __ Gordon Tomlinson [email protected] IM: [email protected] www.vis-sim.com www.gordontomlinson.com ____________________________________________________________________________ __ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, January 29, 2009 9:29 AM To: [email protected] Subject: [osg-users] How to deduce the implied size of texture from coordinate mappings.... 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 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
