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extract geometric information from 3D model files such as .max

Posted on 2004-09-12
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Last Modified: 2010-04-06
I am going to do a project to analyze on 3D models so as to render images of all critical views which can sufficient represent the 3D models without occlusion.

However, I am not clear about what data I need from the model file and also how to extract this data out from the model file.

Could anyone give some advice to me? Thanks a lot!
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Question by:kakameimei
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Expert Comment

by:j3one
ID: 12040185
Well, you will nead to load the model into a render program or a 3d aplication to select the cammera angles you will use. Are you writning your own render program to evaluate the models, or can you use a normal 3d package... ie 3ds max, lightwave, maya, Acad....
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by:kakameimei
ID: 12040531
My first goal is to write a program to evaluate the models.
But before doing this, I need to know more background knowledge about how to analyze the 3d models or what files should I do analysis on now. For example, I would able to know which angles are important for me to take an images so that all of the images i took can be sufficient to represent the 3d models.
Finally, I will use these images as the input to do an Image Based Rendering.
I want the number of images to be just sufficient, but not too many because there are already some methods which sample the models in regular orientation.

My goal is that the camera angles to be used will be determined by the program after evaluating the models.

I can use a noraml 3d package. But one thing I am concerning is that I can evaluate the 3d models manually but not by the program if I use e.g. 3ds max ONLY. I think I may need to use 3ds max, i am not sure. But, how to read some information of the .max behind the application? (<--- sorry, i dont know whether this question makes sense, what i am thinking about is to get more fundamental information of the models)
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j3one earned 150 total points
ID: 12044921
I think I follow, and I would definantly suggest 3ds max. As far as determining the camera angels just by evaluating the      , I would set it up to find the most complex facing of the geomotry, which in most cases will be the best angle to render from. In other words do a poly count and then calculate the bset angle within a set degree that will capture as many pollys as possible.
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Author Comment

by:kakameimei
ID: 12046901
Thanks a lot! You had given me good ideas!

However, how can i count the number of polys? where can i get this information?

Thanks again.
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Assisted Solution

by:Jaime Olivares
Jaime Olivares earned 50 total points
ID: 12068854
You can export your file to VRML (.wrl) format. It is a readable text format. It have two main sections:
3D vertices and 3d surfaces, besides color and texture info.
You can open and manipulate in almost any programming language. Here is an example in Visual C++:
http://www.codeproject.com/opengl/wrl_viewer.asp
Take care about VRML version because file structures are different between 1 and 2 version.
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by:j3one
j3one earned 150 total points
ID: 12081272
Jame has the right idea I think... Basicaly you can find it different ways, as per 3ds max there is a option in one of the menu's to get the poly count, I think you can even pull out a tab that updates as you      . As for your evaluation program, you will have to break the modol down some how to extract the surface info. If you had the program convert a copy to VRML, anylize that data to retrieve the poly count and surface area, then make the program take that data and calculate the camera angle. If you have some more detailed info on the structure of your program, that might help us find the best way to move and anylize the data..

Anyway, hope that helps - j3one
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Expert Comment

by:Jaime Olivares
ID: 12083955
To convert to VRML you can use CtrlView:
http://www.ctrlview.com/download.html
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Author Comment

by:kakameimei
ID: 12085748
Thanks a lot for all your helps! Let me try it out first.
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Expert Comment

by:j3one
ID: 12089513
Best of luck :-)
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