Don't make me write a utility to construct these individual plate pieces
from a patch and then glue them together!


Ron Parker wrote in message <37a1e310@news.povray.org>...
>On Fri, 30 Jul 1999 09:59:43 -0700, Ken wrote:
>>  Problem you have here is that you have pretty much defined the problem
and
>>there is no real solution other that using solid construction methods.
Finite
>>patch primitives are useful little buggers but the one or two restrictions
>>they have can be a bother. You can't even use them in CSG operations to
>>carve out shapes from the solid primitives with and their thickness is so
>>thin they make poor refractive objects (boo oho).
>
>Not so.  Render the scene below and you'll see what I mean.
>
>The first cube (from the left) is made of six bicubic patches with no
>interior, for reference.  The next cube is made of six "unrelated"
>bicubic patches, each with its own interior.  The third cube is a
>union of bicubic patches, with one interior for the whole union.
>The last cube is a box, again for reference.
>
>Notice that the third and fourth cubes have the same basic refractive
>characteristics.  The second cube is broken because POV can't make the
>correlation between the distinct patches and their interiors, so it
>bends the ray upon entry to the first patch but hitting subsequent
>patches has no effect because they have the same ior as the material
>that the ray is already traveling through.  POV interprets this as
>"entering a new object" instead of "leaving the object we were in"
>because it uses the interiors to distinguish one object from another.
>Since the patches have different interiors, they are different
>objects.
>
>So, you can use patch objects to do refraction.  You just have to
>be careful.
>
>----------------- cut here ------->8===========
>
>camera {location <-1,5,-5> look_at -x}
>light_source {<-20,20,-20> rgb 1 shadowless}
>light_source {<20,20,-20> rgb 1 shadowless}
>
>plane {y,0 texture {pigment {checker rgb .5,rgb 1}} rotate 30*y}
>
>#declare patch=bicubic_patch { type 1 flatness .1 u_steps 3 v_steps 3
>                <-.5,-.5,-.5> <-.4,-.5,-.5> <.4,-.5,-.5> <.5,-.5,-.5>
>                <-.5,-.4,-.5> <-.4,-.4,-.5> <.4,-.4,-.5> <.5,-.4,-.5>
>                <-.5,.4,-.5> <-.4,.4,-.5> <.4,.4,-.5> <.5,.4,-.5>
>                <-.5,.5,-.5> <-.4,.5,-.5> <.4,.5,-.5> <.5,.5,-.5>
>              }
>
>#declare pig=pigment {color rgbt .7}
>
>//cube 1
>object {patch rotate 000*x translate y-4*x texture {pig}}
>object {patch rotate 090*x translate y-4*x texture {pig}}
>object {patch rotate 180*x translate y-4*x texture {pig}}
>object {patch rotate 270*x translate y-4*x texture {pig}}
>object {patch rotate 090*y translate y-4*x texture {pig}}
>object {patch rotate 270*y translate y-4*x texture {pig}}
>
>//cube 2
>object {patch rotate 000*x translate y-2*x texture {pig} interior {ior
1.3}}
>object {patch rotate 090*x translate y-2*x texture {pig} interior {ior
1.3}}
>object {patch rotate 180*x translate y-2*x texture {pig} interior {ior
1.3}}
>object {patch rotate 270*x translate y-2*x texture {pig} interior {ior
1.3}}
>object {patch rotate 090*y translate y-2*x texture {pig} interior {ior
1.3}}
>object {patch rotate 270*y translate y-2*x texture {pig} interior {ior
1.3}}
>
>// cube 3
>union {
>object {patch rotate 000*x translate y texture {pig}}
>object {patch rotate 090*x translate y texture {pig}}
>object {patch rotate 180*x translate y texture {pig}}
>object {patch rotate 270*x translate y texture {pig}}
>object {patch rotate 090*y translate y texture {pig}}
>object {patch rotate 270*y translate y texture {pig}}
>interior {ior 1.3}
>}
>
>// cube 4
>box { -.5 .5 translate y+2*x texture {pig} interior {ior 1.3}}
>----------------- cut here ------->8===========
>

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