RE: LOD and "selected" Callbacks

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BOCCARA Michael (MICHAEL.BOCCARA++at++siege.aerospatiale.fr)
Thu, 4 Sep 1997 13:14:29 +0200

  You are setting traversal callbacks for APP process, but ALL the children of
a LOD are APP-traversed. The evaluation of the current LOD is made in the
CULL process. I believe, but am not sure, that all the children are also
CULL-traversed. But only the curent LOD (according to cam-obj distance) is
DRAW-traversed.
So it would not be surprising that all your printdata%d functions should be
called.

Considering your request of evaluating the active index of a LOD, you can do
it it a APPorCULLorDRAW callback, using the pfLOD::evaluate, and the curret
transformation matrix supplied by pTraverser :

lod->setTravFuncs(PFTRAV_APP, NULL, getInfo);

int
getInfo(pfTraverser* trav, void* )
(
  pfMatrix mat;
   trav->getMat(mat);
  pfLOD *lod = (pfLOD*)trav->getNode();
  float i = lod->evaluate(trav->getChan(), mat);
   print(i);
)

is it what you are looking for ?

Mike
_______________________________________________________________________________
_
De: P=INTERNET; DDA.TYPE=RFC-822; DDA.VALUE=guest(a)holodeck.csd.sgi.com le
Jeu 4 Sep 1997 7:02
Objet: LOD and "selected" Callbacks
A: P=INTERNET; DDA.TYPE=RFC-822; DDA.VALUE=info-performer(a)sgi.com; BOCCARA
Michael

I have created an LOD that, in turn, has 4 geodes as children. As with
normal LOD operation, different children are displayed, depending on
the camera object distance.

I have also attached to each geode, a callback:

    for( i = 1; i <= numLOD; i++)
    <
        geode[i] = pfNewGeode();
        gset = createTorusGSet(arena, numPieces, numPoints, 1.0f);
        pfAddGSet(geode[i], gset);
        pfAddChild(lod, geode[i]);
        if(i == 1)pfNodeTravFuncs(geode[i], PFTRAV_APP, printData1,NULL);
        if(i == 2)pfNodeTravFuncs(geode[i], PFTRAV_APP, printData2,NULL);
        if(i == 3)pfNodeTravFuncs(geode[i], PFTRAV_APP, printData3,NULL);
        if(i == 4)pfNodeTravFuncs(geode[i], PFTRAV_APP, printData4,NULL);

       /* etc */
>

When I run the code and move the mouse, the correct image appears as
expected. Further, the correct function is called. However in addition
to the correct function being called, the first function, printData1(),
is ALWAYS called, regardless of which geode is being displayed.
Essentially,

if LOD-3 is displayed, printData3() and printData1() are both called.
if LOD-4 is displayed, printData4() and printData1() are both called.

Basically, what I want is for a different callback to be called depending
on which geode is displayed.

As an alternative...
It would be ideal if there was a function:

       (int) current_lod_index = pfGetCurrentLODIndex(lod)

that I could call as a LOD was being traversed. Then, based upon that
index, I call my appropriate function.

Naturally, the easiest way may be to calculate the LOD-center to Camera
distance, and call a function manually. However, it would be cleaner
if I could automate the process without an additional if test.

(and to be more direct, what I really want is for the function to be called
on LOD passage. Meaning, as LOD-1 is visible printData1() is called ONCE

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