Re: [Algorithms] Sphere to Triangle overlap check

[Jon W. <jw...@gm...>]

If memory serves, you don't need to do all those square roots and normalizes
if you use the barycentric coordinate method.
Also, the radius of the projected circle is sqrt(sphereRadius -
abs(distanceToPlane)) -- you have a sign error in the case the sphere is
above the plane (and the distance is positive).

Sincerely,

jw

--
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On Wed, Jul 28, 2010 at 7:41 AM, Mark Wayland <wa...@in...>wrote:

> Zaf,
>
> First find the distance of the sphere center from the plane. If the abs
> distance is greater than the radius then  there is no overlap.
> You then need to find the radius of the circle of intersection with the
> plane which is much easier than you think. The radius of intersection is
> simply sqrt(sphereRadiusSqr + centerDistFromPlane). Then find the distance
> from the sphere center projected onto the plane to each edge. If the
> distance is less than the radius of intersection then there's an overlap.
> To find the distance to the edge, calc edgeNormal via
> normalize(cross(faceNormal, edge)) then calc (projectedCenter -
> edgeStartVertex) dot edgeNormal.
> This was all from memory and a quick scribble so hopefully it's correct :-)
>
> Cheers,
> Mark
>
>
> On 28/07/2010, at 9:34 PM, Zafar Qamar <zaf...@co...>
> wrote:
>
> > Hi,
> > This is a very old question but I can't seem to find a good answer for it
> and I've searched the net for quite a while.
> >
> > I need a precise way of checking if a sphere and a given triangle have
> _any_ overlap.
> > Specifically, the case I'm struggling with is when the sphere just
> overlaps one of the edges.
> > Also, I need to cater for when the sphere is completely inside the
> triangle, and vice-versa
> >
> > Help please? Or a decent internet link would be much appreciated
> >
> > Cheers
> > Zaf
> >
> >
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