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3D Meshes and CSG operations |
| category: code |
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How to realize CSG operations in 3D mesh objects? Please, discuss the principles. |
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Depends.exe on what you are doing.
3D mesh objects as in triangle meshes? I guess there are tons of papers on that topic and a lot of different approaches... google it.
Or just take distance fields instead - in distance fields CSG is trivial ;) |
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Clip the triangles against each other, check inside/outside rules for each resulting polygon. Simple in theory, but turns into absolute hell in reality due to floating point accuracy. There's a reason why there's very few CSG-packages out there that can eat it's own dog-food. |
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Maybe an easier place to start: Screen Space CSG? |
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OpenCSG uses some image-based method. |
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Indeed, screen-space CSG is much easier to get robust. |
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This reminds me.. I wonder if anyone ever made a .pov ---> random-polygon-object-format converter, e.g. something that would eat povray's script (even with limited set of primites) and output an approximation as a mesh. |
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Just a first random pick... http://www.nigels.com/research/ there's really a huge amount of academic research out there...
Or if you wanna just cut out planes, you have it nearly for free in OpenGL, see for instance http://www.cs.duke.edu/courses/fall00/cps124/web/links.html.
Hmm, distance functions are lovely...
must... download... framework... and play! |
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The easiest one to implement is:
http://www.opengl.org/resources/code/samples/advanced/advanced97/notes/node11. html |
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Easy peasy. Intersect all edges of mesh A with triangles of mesh B and vice versa. Then just connect the dots :)
Bonus points doing the intersection stuff so that each pair or triangles intersect at either 0 or 2 points, retriangulating without nasty singularities and getting intuitive results on non-perfect input meshes. |
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bsp trees will help you with csg:
A Tutorial on Binary Space Partitioning Trees
BSP FAQ
flipcode article
also there's example code in Game Programming Gems 5, if you need it, I'll send you the source code |
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Weeks struggling for a stable connection...
Thanks for the answers.
Ized: Would you mail me it? dang...@gmail.com |
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http://www.opengl.org/resources/code/samples/advanced/advanced97/programs/csg.c |
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with something resembling to an authority, i can confirm that you really don't want to code triangle-mesh CSG yourself. However, if you still insist to do it, I can recommend 216's method above :) |
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I need it and I want it. D: |
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