BRL-CAD provides more than two dozen types of geometry ''primitives'' such as ellipsoids, boxes, and cones. Every primitive is described by a collection of callback functions, for example rt_ell_bbox() returns the bounding box dimensions for an ellipsoid. Wikipedia, Wolfram Mathworld, and various other math sites (and research papers) around the web include the equations for most of our basic primitives while others are a little more tricky to compute.
References:
- http://en.wikipedia.org/wiki/Surface_area
- http://mathworld.wolfram.com/
- http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0274936
- include/raytrace.h: See ft_surf_area callback defined in the rt_functab structure
Code:
- src/librt/primitives/brep/brep.cpp (implement your function here)
- src/librt/primitives/table.c (add a reference to your callback function here )
This task involves writing a new callback function that takes an rt_db_internal object and calculates the surface area (units are mm^2). There are numerous examples in our code where we compute surface area for other primitives. Submit a patch file the may be applied cleanly.
If you succeed, a follow-on task may be created to enable and validate your function.
| File name/URL | File size | Date submitted | |
|---|---|---|---|
| brep_surf_area.diff | 1.9 KB | December 22 2013 16:54 UTC | |
| brep_surf_area.diff | 1.9 KB | December 22 2013 18:10 UTC | |
| brep_surf_area_check.diff | 1.9 KB | December 22 2013 18:18 UTC |
I would like to work on this task.
This task has been assigned to MirceaS. You have 72 hours to complete this task, good luck!
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openNurbs offers a method to convert Nurbs to an approximated polygonal Mesh. Is calculating the surface area of this mesh good enough or do you want a more elaborated solution?
I would like to work on this task.
This task has been assigned to Andromeda Galaxy. You have 72 hours to complete this task, good luck!
The work on this task is ready to be reviewed.
This is the right basic approach, but note that AreaMassProperties() does nothing. The Rhino folks remove the code for that function. Also, you access m_mass, but should be accessing mp.Area() instead.
Fix the m_mass issue and while surface areas still won't work, we can call this GCI task complete (and consider a follow-on to implement ON_Surface::AreaMassProperties()).
One of the mentors has sent this task back for more work. Talk to the mentor(s) assigned to this task to satisfy the requirements needed to complete this task, submit your work again and mark the task as complete once you re-submit your work.
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