W in a uv coordinate is normally 1.0 unless you've projected a point to produce the uv. In that case w needs to be divided out of the uv values to get the real uv, and this is not done until the poly interpolation/shading stage to preserve correct perspective. Again, this matches OpenGL. Renderman/Reyes renderers don't require this - micropolyons are usually gouraud shaded as the perspective interpolation errors are not perceivable at the micropoly scale.
-jonathan On Feb 28, 2012, at 5:58 AM, Julik Tarkhanov wrote: > > On 27 feb 2012, at 18:27, Jonathan Egstad wrote: > >> UV's are a Vector4 so that 3D texture volumes can be supported. They're not >> currently but it seemed prudent to not design in a limiting factor to the uv >> attribute. It also matches OpenGL. >> >> Just set Z to 0, it should be ignored by the current shading system. >> >> fwiw the ordering of the vector is defined in the Vector4.h header file - >> x,y,z,w. > > > Ok Jonathan thanks for the explanation! What would we all do without your > insights :-) > I wonder what Is the W doing here - normal direction override?.. > > -- > Julik Tarkhanov | HecticElectric | Keizersgracht 736 1017 EX > Amsterdam | The Netherlands | tel. +31 20 330 8250 > cel. +31 61 145 06 36 | http://hecticelectric.nl > > > > > > _______________________________________________ > Nuke-dev mailing list > [email protected], http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
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