Re: pfLightSource and pfFrustum

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John Rohlf (jrohlf++at++tubes)
Fri, 26 Jan 96 9:44:23 PST

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In reply to: Philip Nemec: "memory and multiple processes"

>
> On Jan 24, 5:10pm, John Rohlf wrote:
>
>
> > To avoid z-fighting, make sure you either have a local light
> > or are using a local pfLightModel. This is a RealityEngine
> > bug/feature.
>
> Does it mean it's not possible to properly cast shadow from an infinite light
> source like the sun?

        Yes and no. You can use an infinite GL light(with localviewer) but
        the pfFrustum you specify has an origin which defines the point
        from which the shadows are cast. I suppose you could place the
        origin really far away but make sure to use a small FOV and
        large near plane.

>
> > > Since objects are moving, is it necessary to recompute the frustum every
> > > iteration?
> >
> > No.
>
> You mention the frustum doesn't need to be recomputed, but since the light
> source and objects are moving, the frustum will inevitably need to be adjusted
> to these new conditions.

If the pfLightSource is under a pfDCS you do not need to update
the pfFrustum.

> However, how should the frustum of a conic local light
> source be specified? Should it fit the cone and should the far plane correspond
> to the range where the light emitted by the source is totally attenuated?

Yes.

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In reply to: Philip Nemec: "memory and multiple processes"

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