Hello Everyone!
We are currently developing a visualization for a complex geographical
model. To visualize the different forms of landusage we use some VRML
models like industrial buildings, different kinds of trees and so on. To
get a good visual quality in combination with high performance we wanted
to use the Level-of-Detail feature of OpenSG.
But we get a serious performance breakdown when using our VRML models,
and I don't think it hat to do with the polygon count of the models.
When zooming far out so that you can see the whole scene, there are
exactly 816 (LOD-)objects and they all switch correctly to the lowest
resolution, which means about 60 polygons per object. So there are
816x60=48.960 polygons, which is not that much considering that we are
using quite a powerful machine. But switching on the objects decreases
the framerate from about 100fps to 11fps! We also have a iso-surface
visualization to visualize weather data. It's got about 60.000 polygons
and decreases the framerate only about 5 fps.
I already tried not to use the LOD-Node but to load only the low-res
models (see below) and use them directly. Same effect: A significant
performance breakdown that can not be explained be the polygon count.
Here is the code fragment showing the loading of the VRMLs and the
creation of the LODs:
NodePtr ntree[DetailLevels];
ntree[1] = SceneFileHandler::the().read(ntreefilename1);
ntree[2] = SceneFileHandler::the().read(ntreefilename2);
ntree[3] = SceneFileHandler::the().read(ntreefilename3);
[...]
for (i=0;i<DataStore::dataWidth;i++) {
for (j=0;j<DataStore::dataWidth;j++) {
if (trees[i*DataStore::dataWidth+j]!=0) {
ttrans[l]=Node::create();
ttrans_core[l]=Transform::create();
treelodNode[l]=Node::create();
treelodNodeCore[l]=DistanceLOD::create();
// create the nodes for the LOD-Geometry
// 1st
treeGeoNode1[l] = ntree[1]->clone();
// 2nd
treeGeoNode2[l] = ntree[2]->clone();
// 3rd
treeGeoNode3[l] = ntree[3]->clone();
// Create a LOD-Node...
beginEditCP(treelodNode[l], Node::CoreFieldMask |
Node::ChildrenFieldMask); {
{
treelodNode[l]->setCore(treelodNodeCore[l]);
treelodNode[l]->addChild(treeGeoNode1[l]);
treelodNode[l]->addChild(treeGeoNode2[l]);
treelodNode[l]->addChild(treeGeoNode3[l]);
}
endEditCP(treelodNode[l], Node::CoreFieldMask |
Node::ChildrenFieldMask);
// Set the LOD-Node-properties
beginEditCP(treelodNodeCore[l], DistanceLOD::CenterFieldMask
| DistanceLOD::RangeFieldMask);
{
treelodNodeCore[l]->getSFCenter()->setValue( Pnt3f(0, 0,
0) );
treelodNodeCore[l]->getMFRange()->push_back( 5.0 );
treelodNodeCore[l]->getMFRange()->push_back( 20.0 );
treelodNodeCore[l]->getMFRange()->push_back( 40.0 );
}
endEditCP(treelodNodeCore[l], DistanceLOD::CenterFieldMask |
DistanceLOD::RangeFieldMask);
// Matrix for translation
m.setTransform(Vec3f(j,punkte[i*DataStore::dataWidth+j].y()+diff,i));
// multiplicate with Scale-Matrix
m.mult(scale_matrix);
beginEditCP(ttrans_core[l]); {
ttrans_core[l]->setMatrix(m);
} endEditCP(ttrans_core[l]);
beginEditCP(ttrans[l]); {
ttrans[l]->setCore(ttrans_core[l]);
ttrans[l]->addChild(treelodNode[l]);
} endEditCP(ttrans[l]);
beginEditCP(tree_root); {
tree_root->addChild(ttrans[l]);
} endEditCP(tree_root);
l++;
}
}
}
In the ttrans[l]-EditCP section I replaced the
addChild(treelodNode[l])with addChild(treeGeoNode1[l]) to test the
performance when using only the low-res object without the LOD-feature.
Are there any known problems when using many loaded 3D-objects? Or
should we try to somehow use a kind of 'shared geometry'? If not what
could be the reason for the performance breakdown?
Any hint will be greatly appreciated!
Bye,
Jens Freisen
--
University of Paderborn
Department of Computer Science
Paderborn, Germany
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