Re: Returning modified data from a forked ISECT test

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Mario Veraart (rioj7++at++fel.tno.nl)
Fri, 31 Oct 1997 16:01:45 +0100 (MET)

> I am having problems returning data from a forked ISECT process.
> After using pfPassIsectData to copy data used by an intersection
> function I am assuming a call to pfGetIsectData will transfer data
> modified
> by the intersection function back to the APP data structure .
> However upon inspection of the data returned, nothing has changed even
> although I most definitely changed the data (see example source test.c).
>
> Is pfGetIsectData the right funtion to transfer the data back or am I
> missing something here.
>
> Whilst on the performer subject ,this one must surely have been asked.
> Why does the system lock when I try to pfuLockDown - (APP,CULL,DRAW
> p=1,2,3)-
> on our InfiniteReality ? I also try to pfuRunProcOn the ISECT stage on
> p0.
> I asked SG's Clive Harding who's investigating and he could repeat the
> problem
> with perfly so it's not just me. This problem does not occur on a RE2
> machine.
>
> --
>
> Peter Smithies, Software Engineer,
> Intersim Limited, Units 7-8, Thorgate Road, Littlehampton. Sussex. UK
> Tel: +44 (0)1903 733428 Fax: +44 (0)1903 730246
> email: modellers++at++intersim.co.uk Internet: http://www.intersim.co.uk
>

What I do is use shared memory to give the data back.
The function pfGetIsectData() returns a pointer to the copy of the
isect data that APP has. APP makes a copy of it and gives it to ISECT
when you call pfPassIsectData(), at the next call to pfFrame().
A new call to the isectfunction is made when pfPassIsectData() was
called.
My sceme is use shared memory to let the APP know that ISECT has done
the calculation and then set up new data in the IsectData and call
pfPassIsectData().

    if (shared->isectReady) {
        ... process previous isect data
        ... setup new data for isect
        shared->isectReady = FALSE;
        pfPassIsectData();
    }

My question about a forked ISECT process:
The isect function is called ones before the first call to pfFrame().
I have the impression it happens in the pfConfig() call.
Does anybody know if this is true.

Mario
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