> hi all ogl guys out there.
> my problem:
> i am rendering a world using octrees.
> i have frustrum culling, but the framerates are to low.
> my idea: only render visible parts.
> but, how can i determinate the visibility
> by using this octree ?
> or how to modyfy the octree for this
> occlusion culling ?
> thanks for your answers
I don't have any good answers to your questions but my own approach to
visibility determination is to calculate the PVS (Potentially Visible Set)
for each cell of the octree. To make that job easier I partition the octree
into a series of quadtrees first. Each quadtree represents a two-dimensional
world with solid and empty cells. I calculate the PVS for each empty cell,
which is essentially a two-dimensional problem. Once the PVS is complete you
can extract visibility information from each cell at run-time. First you
locate the cell in which the camera is located. Once you know what cell
you're in you can extract the visibility information for that cell. That
information will tell you what cells are visible from that cell. Then you
only draw the cells that are visible.
To try and explain an algorithm for calculating PVS here is futile. All I
can suggest is that you try to simplify the problem by dealing with
two-dimensional quadtree slices of octree. But even then you may have no
success. It is probably best that you do some research on computational
geometry first before you attempt to crack this problem.