Ron Parker wrote:

> > I asked yesterday when I could have a copy of the new version
> > of the "Super Patch" and was told to "bugger off" (so to speak :).
> 
> You were not.  I was joking, as I thought you were.  Furrfu.  I really
> don't know when it will be online, it depends heavily on what else is
> going on in my life.  Nevertheless, every time I mention it I get asked
> when it's going to be back online, despite the fact that I've said more
> than once that I really don't know.

I was taking yet another friendly swipe when I mentined the above.

> If you're intersecting a ray with a planar mirror, trace isn't really
> necessary because the operation is so simple.  Here's a macro to find
> it, borrowed somewhat from the POV source.
> 
> #macro IntersectPlane( _PlaneNormal, PlaneOffset, RayInitial, _RayDirection )
>   #local PlaneNormal=vnormalize(_PlaneNormal+<0,0,0>);
>   #local RayDirection=vnormalize(_RayDirection+<0,0,0>);
>   #local NormalDotDirection = vdot(RayDirection, PlaneNormal);
>   #if ( abs(NormalDotDirection) < 0.00001 )
>     #error "Ray parallel to mirror"
>   #end
>   #local NormalDotOrigin = vdot( RayInitial, PlaneNormal );
>   #local Depth=(PlaneOffset - NormalDotOrigin) / NormalDotDirection;
>   RayInitial+Depth*RayDirection
> #end
> 
> Of course, this assumes you haven't done anything with the mirror, like
> rotating or scaling it.  If you've done that, you'll have to fix the
> normal and offset appropriately.
> 
> Translate is
>   #declare Offset=Offset+(Normal*Translation);
> 
> Rotate is trickier - you have to multiply the normal vector by the
> transpose of the rotation matrix.  If you rotate before you translate,
> though (and you probably will) you can no doubt find an easier way to
> find the new normal.  Hope this all helps.

  I think I have a simple yet elegant solution in the works. Since
I have abandoned the photon technique in favor of simply connecting
cylinders from each mirror surface to the next John Van Sickles
connect the dots macro handles it well and I know how to use it
from previous experience.

  Thank you for taking the time to offer assistance.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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