This is an interesting concept.  Anyone know if there's any precedent for
doing this (any other renderers that use this technique)?  But might this
just become a form of spherical mapping?

-Nathan

Mathias Broxvall wrote:
> 
> Hi!
> 
> I think I have an idea how to make "UV mapping" for
> arbitrary objects. The current versions of it only
> seem to work for bezier patches and a few other
> objects (does it work with CSG?)
> 
> Please note that with "transformations" I mean
> arbitrary nonlinear transformations of objects (CSG,
> animated blobs etc...)
> 
> 1. The user specifies the object before and after any
> transformations and a few center points.
> 
> 2. From the centerpoints a set of rays are shot out.
> Where they intersect the untransformed object the
> controll points c0,c1,c2,... are formed and where
> they intersect the transformed object the controll
> points c'0,c'1,... are formed.
> 
> 3. When applying texture to a point <x',y',z'> on the
> tranformed object write <x',y',z'> as a linear
> combination of the few closest controlpoints
> 
>    <x',y',z'> = a * c'i +  b * c'j + d * c'k.
> 
> Calculate the "untranformed" point
> 
>       <x,y,z> = a * ci + b *cj + d * ck
> 
> And use the texture given at that point.
> 
> Example of how it could be used:
> 
> difference {
>   sphere { <0,0,0>, 10 }
>   sphere { <10,0,0>, 2 }
> 
>   texture {
>     transformed {
>        original sphere{ <0,0,0>, 10 }
>        original_centerpoints { <0,0,0> }
>        center_points { <0,0,0> }
>        control_density 10
>     }
>     <my favourite texture....>
>   }
> }
> 
> Of course this doesn't work with to few controlpoints,
> to large transformations ,porly choosen "centerpoints"
> or very irregular objects. But perhaps it works in most
> normal cases with a smart user.
> 
> What do you think? Should I (try) to implement it?
> 
> / Mathias Broxvall

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