[vtkusers] create a texture map for an arbitrary surface

[John Biddiscombe]

Tim,

> If you have a routine 
> that allows the 
> user to paint the pixels in the texture image by pointing at 
> the teapot 
> with the mouse then the paint they apply may appear not only 
> where they 
> want but also somewhere else on the teapot! The same is true 
> of the other 
> TextureMapTo* filters.

OK. So you want to explicitly give cell number N, texture coords u1,u2,u3...
cell N+1 completely different coords (not necessarily spatially related to the previous cell)

PolydataIn->Map Cells to arbitrary texture space ->Polydataout
where "Map Cells to arbitrary texture space" efeectively does a mapping and point duplication (if necessary) for every cell based upon the specified (or user generated) cell->tex table.

hmmm....

no, there's no easy way I don't think. Or at least no way that doesn't involve you doing all the cell manipulation yourself - the actual implementation wouldn't be too bad (lots of clesses like normal generation with splitting on do point duplication and you could use most of that code). Getting the cell->tex mapping that's needed as input would be a serious pain though!

$0.02

JB


> 
> I was wondering if there was some standard way of mapping an 
> arbitrary set 
> of polygons to the unit square of the texture image such that 
> no polygon 
> overlaps with any other. My idea was simply to map the 
> triangles onto a 
> grid (http://www.eastman.ucl.ac.uk/~thutton/tri_grid.jpg) but 
> I wasn't sure 
> if that was a good idea and was wondering if anyone else knew 
> of a way to 
> approach this. Of course multiple texture images is one solution.
> 
> I'm not actually writing a painting routine, I just want to texture a 
> surface such that each bit of surface gets its own bit of 
> texture (for 
> human faces).
> 
> Tim.
> 
> 
> 
> At 10:27 22/07/2003 +0100, John Biddiscombe wrote:
> >Tim,
> >
> >What do you mean? TextureMapToPlane effectively maps a unit 
> square to your 
> >dataset (you supply the extents of the plane though). In 
> what way will you 
> >be doing things different?
> >
> > > My thought is to simply map the list of triangles (ideally
> > > polygons) onto
> > > the unit square using a grid layout
> >
> >Care to elucidate?
> >
> >JB
> >
> > > -----Original Message-----
> > > From: Tim Hutton [mailto:T.Hutton at eastman.ucl.ac.uk]
> > > Sent: 21 July 2003 16:56
> > > To: VTK Users
> > > Subject: [vtkusers] create a texture map for an arbitrary surface
> > >
> > >
> > > Hello vtk users,
> > >
> > > I would like to create a texture map for an arbitrary
> > > polygonal surface
> > > (for example, to enable painting of any 3D object) - is there
> > > an easy way
> > > to do this in VTK? I don't want to use vtkTextureMapToPlane
> > > or similar
> > > because these don't guarantee a unique bit of texture for
> > > each part of the
> > > object.
> > >
> > > My thought is to simply map the list of triangles (ideally
> > > polygons) onto
> > > the unit square using a grid layout, and use that for the texture
> > > coordinates (duplicating vertices as necessary). Has anyone
> > > done something
> > > similar? Would such a class be useful in VTK?
> > >
> > > Thanks,
> > >
> > > Tim.
> > >
> > >
> > > --------------------------------------------------------------
> > > -------------
> > > Tim Hutton,
> > > http://www.eastman.ucl.ac.uk/~dmi/MINORI
> > > Research Fellow & PhD student,
> > > T.Hutton at eastman.ucl.ac.uk
> > > MINORI Project, Biomedical Informatics Unit,
> > > Eastman Dental Institute, UCL,                   Tel: [+44]
> > > (0)20 7915 2344
> > > 256 Gray's Inn Road, London WC1X 8LD, UK         Fax: on request
> > > --------------------------------------------------------------
> > > -------------
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