Le 2013-02-11 12:40, Warp a écrit :
> Alain <kua### [at] videotronca> wrote:
>> The bounding don't work correctly when used in a way similar to an
>> intersection.
>> The bounded object itself is not bounded correctly, it's as if the
>> bounding object is oriented relative to the camera.
>> Next, there is a huge problem with the shadows: Most of the time, the
>> part of the original object OUTSIDE the bounding object still cast
>> shadows, but not always.
>> It's mostly appen when using some infinite primitive, like a quadric,
>> but can also appen if the bounded object is a finite primitive or some CSG.
>
> I haven't tested your scene, but I think you have a slight
> misunderstanding about what bounding objects do.
>
> A bounding object is *not* the same thing as an intersection with an
> "invisible" object. It cannot be used to "cut away" parts of an object
> because that's not how it works (nor is it intended for that purpose.)
>
> What happens is that when a ray is tested against the object, it will
> first be tested against its bounding object, and if it hits that, then
> it will be tested against the actual object. This test doesn't actually
> care where the bounding object is. Regardless of where it is, it just
> tests to see if the ray its hit, and proceeds with the actual intersection
> test only if that was so.
>
>  From this it follows that if the bounding object does not actually fully
> enclose the actual object, you'll get incorrect rendering (the visible
> parts of the object will depend on the orientation of the bounding object
> with respect the direction of the rays' origin.)
>
> If you want to actually clip the object with another, use clipped_by,
> which has been designed for that exact purpose.
>
> And in fact, given that wanting to both bound and clip with the same
> object, there's a handy shortcut, namely "clipped_by { bounded_by }"
>
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