From: Alexandre Naaman (naaman++at++laplace.engr.sgi.com)
Date: 09/14/2001 16:57:21
On Fri, 14 Sep 2001, Dirk Scheffter wrote:
Hi Dirk,
Is it possible that maybe your line segment is not long enough to
intersect the plane? The intersection gets computed as if the line were of
infinite length and then only returns true if it is of the proper length.
That's probably not what you would expect ... but still.
So, could you try checking to see if the distance is either negative or
larger than the length of your pfSeg? just for fun ...
A+,
Alex.
> pfHi there,
>
> I tried to intersect a segment (pointer ray) against a pfPlane.
> For my surprise, I never got a hit. (Return was allways 0.)
> I read the man page again and found out that normal of plane directs
> to exterior of halfspace.
> However, I turned the normal around (z = -1 instead of 1)
> but got exactly the same result.
> Just for fun I used the returned distance and computed the position
> of the hit (that per return value did not occured).
> Oha! The position was exactly the expected.
> Hmmm...
> Is it possible/known that the pfPlane::isect doesn't return the hit?
> (despite of the fact that it seems to compute the correct result)
>
> IRIX 6.5.6, pf2.2.7
>
> pfThanks in advance and have a nice weekend,
> Dirk.
>
> P.S.: To people from U.S.: My heart is with you. Ban the terror.
>
> P.S.2: Well, I constructed the pfPlane with a correct normal:
> pfVec3(0.0f, 0.0f, 1.0f) resp. pfVec3(0.0f, 0.0f, -1.0f).
>
> -----------------------------------------------------------
> Dipl.-Inf. Dirk Scheffter scheff++at++iff.fhg.de
> Fraunhofer IFF fon: +49 (0) 391/40 90-854
> Sandtorstr. 22 fax: +49 (0) 391/40 90-870
> D-39106 Magdeburg http://www2.iff.fhg.de/~scheff
> Germany
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