[Plib-devel] Problem with ssgRangeSelector

[Paolo L. <p.l...@ci...>]

Dear all,

In the rewrite of the useful lodmaker utility in order to make it work =
"by
single leaf"  instead of "by full model" (assuming that two LOD models =
has
the same scene graph structure) I noticed that all the houndreds
RangeSelectors put in the combined result ssg model all suddenly switch =
at
the same time during visualization, thus resembling the original =
lodmaker
bekavior.

By going into the code of ssgRangeSelector::cull, it seems to me too =
simple
and thus not general.

Infact assuming the camera matrix is passed as second parameter to
ssgRangeSelector::cull (is it?), the current code basically only tests =
which
depth range is the camera position in, thus select'ing the corresponding
child subgraph.

I could have misunderstood the code, or the purpose of the subject class
itself, yet I expected it would compare the actual position of an object
(e.g. by its Bsphere center) with the current camera position instead.

I got a much better behavior by changing the way of calculating

  float range =3D sgLengthVec3 ( m [ 3 ] ) ;

With

  const float *center =3D this->getKid(0)->getBSphere()->getCenter();  =
// just
refer to the first LOD
                                                                     // =
for
center information
  float range =3D sgDistanceVec3 ( center, m[3] ) ;

Of course this doesn't still keep into account the transformation path =
of
the node within the graph, which could require a getNetTransform() to
further transform the center.

Is that roughly right? How to proceed? Could it be a topic for the =
upcoming
release? Do I proceed improving and testing it rapidly?

Greetings -

Paolo Leoncini


-------------------------------------------------------------------------=

Paolo Leoncini     phone:  +39 (0823) 623134
Visualization & Virtual Reality   fax:    +39 (0823) 623126
CIRA - Italian Center for Aerospace Researches mailto:p.l...@ci...
Via Maiorise - 81043 Capua (CE) Italy  http://www.cira.it