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.

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

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

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.