Re: preIsectFunc bad trav matrix
Don Hatch (hatch++at++hell.asd.sgi.com)
Wed, 16 Apr 1997 14:10:54 -0700
On Apr 16, 8:26am, Steve Baker wrote:
> Subject: Re: preIsectFunc bad trav matrix
>
> Chehayeb, Nassouh <nchehayeb++at++ceit.es> said:
>
> > The node used to set the traverser CB is a pfDCS with a changing matrix,
> > The result of printing is an Ident matrix instead of the dcs matrix at
> > ISECT time.
> >
> > Am I making a mistake or its a Performer bug?
>
> I think it's a pfBug. I reported a similar problem some time ago - but
> didn't get any kind of response. Eventually I found a work-around.
>
> Here is the note I wrote to myself at the time (over a year ago)...
>
> /*
> SJB: There is some kind of a bug in pfGetTravMat(). In this application,
> there is typically a DCS node somewhere above this node and
> pfGetTravMat() is well behaved. However, if there is no DCS
> (or maybe an SCS?) between the pfScene and this node then
> pfGetTravMat() should return an identity matrix. In fact, the
> X and Y eyepoint coordinates can be found in the bottom row
> of matrix - but curiously, not the Z coordinate!?!
> */
>
> [pfGetTravMat() and pfTraverser::getMat() are of course the same routine.]
>
> If what I discovered back then is still true, then you *might* be able to
> work around the problem by putting a DCS (or perhaps an SCS) at some
> point in the tree above the node with the preIsectFunc() callback.
>
> My code (as it happens) always has a DCS node somewhere above the node with
> the callback - clearly when I wrote that comment, I believed that an SCS
> might work instead.
>
> It would be nice if some kind hearted pfPerson would fix this problem in
> Perf 2.2 or in a patch to 2.0.x/2.1.x
>
As Bernard Leclerc replied earlier, the trav matrix at the DCS node
is not supposed to include the effect of the DCS itself, so
I think the pfGetTravMat() bug you are referring to is
a separate issue (one that we'll try to track down and fix for 2.2).
Don
--
Don Hatch hatch++at++sgi.com (415) 933-5150 Silicon Graphics, Inc.
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