Hi,
I have to make in my app dynamic lines. As far as I know display lists are
deprecated for now on GLES2 platform I try to make it using VBO+EBO, like in
osgparametric,so now it works fine. But I have to draw up to 1000 lines with
100 points so it can be so hard to GPU. So I decided to recalculate EBO using
LOD strategy. So I'll calculate distance to my point and remove odd indices.
Could you please give me some snippet how to work with EBO in update or draw
callback?
Also my lines are trajectories and I have to draw them respectively to
simulation time. But I found that I can't change size of element buffer.
Because I found in PrimitiveSet.cpp
this lines
Code:
void DrawElementsUInt::draw(State& state, bool useVertexBufferObjects) const
{
.......
if (ebo)
{
if (_numInstances>=1) state.glDrawElementsInstanced(mode, size(),
GL_UNSIGNED_INT, (const GLvoid *)(ebo->getOffset(getBufferIndex())),
_numInstances);
else glDrawElements(mode, size(), GL_UNSIGNED_INT, (const GLvoid
*)(ebo->getOffset(getBufferIndex())));
}
}
so here size() - total size of element buffer and I create for example EBO with
200 indices total and want draw only first 100 indices - how can I make it?
for the reference here is my code
Code:
osg::Node* createModel( bool dynamic, bool useVBO)
{
osg::Geode* geode = new osg::Geode;
osg::Geometry* geom = new osg::Geometry;
geode->addDrawable(geom);
osg::Vec3 row(0.0f,0.0f,0.0);
unsigned int num_x = 200;
unsigned int num_y = 20;
unsigned int vert_no = 0;
osg::Vec3Array* vertices = new osg::Vec3Array( num_x );
unsigned int iy;
for(iy=0; iy<num_x; iy++)
{
(*vertices)[vert_no++] = row;
row.y()=1000.0f*iy;
row.z()+=100;
}
geom->setVertexArray(vertices);
osg::VertexBufferObject* vbo = useVBO ? new osg::VertexBufferObject : 0;
if (vbo) vertices->setVertexBufferObject(vbo);
osg::ElementBufferObject* ebo = useVBO ? new osg::ElementBufferObject : 0;
osg::DrawElementsUInt* elements = new
osg::DrawElementsUInt(GL_LINE_STRIP_ADJACENCY_EXT, num_x);
unsigned int element_no = 0;
for(unsigned int ix = 0; ix<num_x; ix++)
{
(*elements)[element_no++] = ix;
}
geom->addPrimitiveSet(elements);
geom ->setDataVariance(osg::Object::DYNAMIC);
geom->setDrawCallback(new DrawCallback());
if (ebo) elements->setElementBufferObject(ebo);
geom->setUseVertexBufferObjects(useVBO);
return geode;
}
...
Thank you!
Cheers,
Roman[/code]
------------------
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http://forum.openscenegraph.org/viewtopic.php?p=28826#28826
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