Re: Using Chromium to extract a scenegraph

I threw together a simple SPU that output each frame to a .ply file,  
but it was such a short program that I didn't really think to release  
it.  Basically I just multiplied each vertex by the modelview matrix,  
and then spat out the eye-space vertices to the file.  I maintained  
the connectivity of the triangles on the side, and dumped those after  
the triangles were done (required by the file format).  I think this  
was less than 100 lines of code in all (use the array spu to avoid  
having to deal with vertex arrays, and the state tracker to keep  
track of colors/normals/matrices).

Doing something hierarchical like a scene graph would certainly be  
useful, but I'm not aware of such a thing.

On Jul 15, 2005, at 8:19 PM, Brian Paul wrote:

> Daniel B. Faken wrote:
>
>> Hi All,
>>   Does anyone have pointers to such work/SPUs?
>>   For example, to convert a 'frame' of some OpenGL-program to  
>> 3DSMax format, .OBJ format, VRML, etc..
>>   It seems like a fairly obvious use, but I can't think of any  
>> work like this.. maybe there are some theoretic limitations?
>>   I suppose in the limit this is something like decompilation.
>>   There is of course file-output.  And the GLDB project which
>> can "capture" an object via a stream-query-language (it hasn't
>> released any software yet though - just the SIGGRAPH'05 paper at
>> http://www.cs.jhu.edu/~jab/gldb.pdf), and my own CRFreezer stuff.   
>> But none of these (AFAIK) attempt to deduce the structure of an  
>> entire scene from the GL stream.
>>   One could look e.g. for gl{Push,Pop}Matrix(), gl{Begin,End}(), gl 
>> {Push,Pop}Attrib(), .. as markers for subtrees in a scenegraph.
>> To extract objects one could look for coincident vertices (and/or  
>> use Chromium's bounding-boxes).
>>
>
> Sounds like that would be an interesting project.  I don't know of  
> anyone who's tried it.
>
> -Brian
>
>
>
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--
Greg Humphreys, Assistant Professor
Department of Computer Science, University of Virginia
http://www.cs.virginia.edu/~humper/