Hi Jason, On Tue, Oct 23, 2012 at 5:27 PM, Jason Daly <jd...@ist.ucf.edu> wrote:
> > There's no difference between these two. ARB_multitexture is a 15-year > old extension that simply provides the specification for how multitexturing > is done. Multitexturing has been part of standard OpenGL since version 1.3. > Ok I see, I stumbled upon this terms when looking at http://updraft.github.com/osgearth-doc/html/classosgEarth_1_1TextureCompositor.html > - using multi-pass rendering. Probably slower but not limited by > hardware. > > > I doubt you'll need to resort to this, but with the vague description of > what you're doing, I can't be 100% sure. > Actually what I do is that I have a mesh that is generated from depth-maps. In a post-processing step I want to apply photos (taken by arbitrary cameras, but with known intrinsics) as textures. What I know is the position of which the photo was taken (relativ to the mesh) and the camera intrinsics. What I do next is to calculate UV coordinates myself using projective texturing. Of course, not all triangles of the mesh get textured by the same photo, and there a triangles that are not visible from any photo. > > If this is true, you can generate the texture coordinates directly from > the position/orientation of the photo and the positions of each vertex in > the mesh. Read up on projective texturing to see how this is done. OSG > can do this easily if you write a shader for it, or you can use the > osg::TexGen state attribute to handle it for you (it works just like > glTexGen in regular OpenGL). > How can TexGen and a shader help here? Would it allow me to calculate the UV coordinates for a given photo (camera position etc.) and the mesh? > > The other thing you'll need to do is divide up the mesh so that only the > faces that are covered by a given photo or photos are being drawn and > textured by those photos. This will eliminate the need for you to have as > many texture units as there are photos. There may be regions of the mesh > where you want to blend two or more photos together, and this is the only > time where you'd need multitexturing. You should be able to handle this > mesh segmentation with a not-too-complicated preprocessing step. > I wanted to avoid splitting the mesh, at least for the internal representation (which I hoped included visualization). Pros and cons have been discussed in this thread (in case you are interested) https://groups.google.com/d/topic/reconstructme/sDb_A-n6_A0/discussion Best, Christoph
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