Hi,

On Tue, 2007-07-10 at 15:26 -0400, Eric Maslowski wrote:
> Hello all,
>   I've read through the archives and documentation, but it seems that there
> is something inherently wrong with my frustum and transparency sorting. (see
> image below) Objects that are clearly distant are drawn in front of closer
> objects, but it also depends on orientation of the camera. Looking at the
> pics it shows me that the objects aren't being sorted properly, but their
> bounding volumes are correct. When visualizing the volumes, I also get a
> strange frustum in the distance. 
> 
> Could this frustum actually be the "cameras" frustum which is somehow
> independent of the camera? (see link below for example movie of it's
> behavior) If so, this would explain some other oddities I'm seeing related
> to culling. Also of note is that if I turn off AutoFrustum the dancing
> frustum disappears when drawing volumes, but I get a warning "left & top
> parallel" and the transparency still issue exists.

form looking at the picture the problematic part is the transparent
surface that covers the ground. 

The problem I can see is that the the sorting happens according to the
bbox centers. So the comparison for sorting will compare the distance 

camera <-> center bbox tree

to 

camera <-> center bbox plane

which given the the center bbox plane is behind the camera for the first
two sets of pictures and the tree bbox center is in front of the camera
gives the interesting result that the sorting flips.

Short question do you use transparency or alpha keying for the tree ?.

Alpha keying might help as it would take the tree out of the
transparency (IIRC).

Another option would be to use the material keys to force a fixed
rendering order (also IIRC I would have to check if the backend does
the right thing)

kind regards,
  gerrit







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