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swordfish

Scene-Graph

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The way I gather it, the best way to implement a scene-graph for use in a real-time graphics engine would be to have a so-called 'object soup' combined with 2 trees (spatial and semantic) that share leaves. Is there any reason why you wouldn't do this? I can't foresee any major problems with this setup. Perhaps someone here has. I've been sitting here for days just racking my brain over it. Any insight would be very much appreciated.

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Maybe that the spatial tree isn't usefull if you have a very simple scene : no alpha-blending pass, no occlusion culling. Elsewise the only drawback I see is that you must do the work twice each time you update an object.

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Hi:
I'm wondering how I go about building a scene graph. Could you point me at some resources? Right now I am using an oct tree, but I cant do back to front or front to back, which I think is needed for alpha blending....I'm curious what the difference between spatial and semantic representations are. Any help would be greatly appreciated!!
:)

--N

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I don't think I explained my situation very well in my last post, so I'll try to be more clear. Presently I build an oct tree data structure in my game so that I can use it for rendering and collision detection optimisation. Works well. However, I am now faced with the predicament of having to render some alpha blended and non-alpha blended polygons, which in turn means I need to order them back-to-front. The oct tree in and of itself has no way to do this. I considered using a bsp tree but what happens if i want to add/remove stuff in real time? I cant rebuild the bsp every time as it would be inefficient.so how do most games/simulations support both dynamic scene data as well as blended polygons?

Thjank you,

--N

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Nekoflux:

Here are some articles/pages which I found useful when implementing my scene-graph.

http://wwweic.eri.u-tokyo.ac.jp/computer/manual/lx/SGI_Developer/books/Perf_GetStarted/sgi_html/ch06.html
http://www.realityprime.com/scenegraph.php
http://www.opensg.org/doc-1.4.0/PageScenegraph.html

Of course there is tons of info on Google. However beware, I found that a lot of articles tend to focus entirely on either the spatial or semantic organization of a scene-graph. For anything real-time (and particularly in your case), you almost definitely want a scene-graph that handles both aspects (I'm sure some people could argue against that).

On that note, I recommend reading any related material by Dave Eberly.

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