Hello Dusten,
I understand how this can be accomplished if a user is given a lot of
control over the scene graph during map/level creation, but what I'm
aiming for is the ability to load in a .3ds model (or otherwise) for
level geometry and let the user place various prefabs such as crates,
trees, cars, etc into the world; then, the composite level is exported
to a .lua script so that it can be loaded again with all of the static
and dynamic objects intact.
You just need to use a modeling tool and format which understand
hierarchy, and then use that. Many formats which normal modeling tools
export support this: COLLADA, OpenFlight, etc. Plus, there are plugins
for both 3DSMax and Blender (among others) to export to .osg directly.
If you need anything else, you need to code it yourself, which shouldn't
be that complicated. Here we have a system which loads and interprets
scripts as you describe, plus it includes physical properties (we
develop and sell a physics engine after all :-) ), viewer configuration,
input device configuration, etc.
Of course, once again the ability to do view frustum culling properly
still hinges on the grouping of close-by objects and a well-conditioned
scene graph, and at this point it's up to your loader to build the scene
graph in a way that will be close to optimal. You can give hints in your
scripting files for this (such as group names, where each object whose
group name is the same will be grouped together, or a radius + number of
objects scheme, where objects which are close by within a certain radius
will be grouped together up to a given number of objects).
The issue is of course, that I cannot
possibly compete with blender or 3dsMax as a modeling program, and I
shouldn't attempt to either. The users of this engine should be able to
use existing, non-proprietary modeling software to create levels or
items for their game.
I totally agree with this. However, slight retraining for the realities
of real-time graphics is often necessary. Why do you think the 3D
artist/multimedia schools have different classes for game modeling and
fx/film modeling? Both have different tradeoffs and the modeler must
keep different things in mind while doing his job. (same goes for
texture artist, lighting artist, etc. when those positions are occupied
by different people)
I believe it would be too complex to implement an
automatic or user-friendly way to disassemble an existing set of level
geometry, only to re-assemble with parenting.
Not only is it not too complex, you don't have any choice. It's up to
you to provide OSG with a well-formed scene graph. If you don't, you
probably won't get great performance. Modeling tools by default make
flat hierarchies, but in both 3DSMax and Blender IIRC (and Maya,
Softimage XSI, etc. too, and of course Creator) there is a view which
allows the modeler to rearrange the hierarchy. Using this, along with a
format which can export the hierarchy properly will save you a lot of
time trying to do the same programmatically.
But it would be -very-
tedious for a level designer to heavily subdivide his or her model for
culling purposes.
It's not that tedious, and I didn't say you need to heavily subdivide.
Just keep the hierarchy in mind when building the levels, and do a rough
grouping. You will see large performance gains.
Is there some way to use a 'precise' bounding box on
a single node, that takes the level geometry's lowest LOD for occlusion
culling operations? At least this would allow detail objects to be
culled away if the camera was 'in' the level, as it usually is.
I'm not aware of anything in OSG to automatically build occlusion
volumes (from anything, not just from the lowest LOD), but then again I
have never used occlusion culling in OSG myself, so others may be better
placed to inform you on this.
If you want my advice, start with making OSG's view frustum culling job
easier, that's the simplest to implement and will already get you
massive gains.
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay [EMAIL PROTECTED]
http://www.cm-labs.com/
http://whitestar02.webhop.org/
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