Hello Maximilian,
Maximilian Haupt wrote:
> I am developing a part of an application that displays additional
> textual information on billboards. To keep them in the foreground, I
> use sortkeys and additionally, I move them close to the user, so that
> they are always on top of all other objects and are selected first.
> This works very well for now in desktop mode.
ok.
> But I experience a strange behavior in Cluster Mode (e.g. two
> side-by-side cameras rendered by two render nodes). When a billboard
> with a high width is moving horizontally from one camera to another
> and starts to be visible on the second camera - at least in theory it
> should be visible - it will not be send to the second cluster node
> first. Only when a huge part of the billboard should be visible on the
> camera, it suddenly also appears on the second node. I expect the
> following fact to be the reason of this problem:
>
> The billboard’s vertices are starting in the lower left corner with
> (0,0) and grow to the right and top. Maybe the clipping algorithm is
> only using the (0,0) point to determine the affected cameras/cluster
> nodes.
hm, what are you using to build the billboards? A Geometry below a
Billboard?
> Therefore, the idea is to create a second geometry with the same
> material that has its starting point in the upper right corner instead
> of the lower left. This way I draw two billboards with the same size,
> but the clipping algorithm should send any of them to the cluster
> nodes and there should always be a visible billboard on all cameras -
> even in the overlapping areas.
urgh, apart from being ugly this workaround also has the potential to
show artefacts from depth fighting between coplanar polygons.
> This is a bad workaround and increases the number of triangles in the
> scene. Is there a more straightforward solution? Maybe disabling
> clipping on the billboards or something similar?
well, if the problem is incorrect culling of billboards, I'd say the
best solution is to fix that ;) ;)
For that I'd appreciate it if you could provide some information how
your billboards are built, i.e. which classes you use, how the relevant
parts of the scenegraph look like.
As a workaround and to confirm that the bounding volumes/culling are the
problem you could just make the bounding volume of your billboard very
large and mark it as static - you can also try to mark it as infinite,
but I vaguely recall some problems with that a while back;
see Volume::setStatic() Volume::setInfinity().
Cheers,
Carsten
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