Sorry for not getting back to you earlier, but work has intervened. I haven't been able to grab the software licence for Rapidform, as it is being used for commercial work right now. Our training session is organised for next week, so I'll see what I can do then.
I notice your Redwood Creek Giant mesh is a bit concave at the top ?
My volume solution for RCG is now about 1% from your RapidForm XOR now using a "best fit" strategy for the missing points (that always arrive in cloud maps). I used a conservative linear interpolation between closest surface edge points. In my experience I have found that spline interpolation over-estimates tree surfaces so that was not used here.
The concavity may be a function of the meshing algorithims and/or floating point accuracy on the model. A linear interpolation betwen points is pretty much what a tet-mesh is. More advanced analytical methods for stress analysis (e.g. finite element methods) will use polynominal (2nd order) interpolation of tet and quad meshes to obtain a more realistic model stiffness.
Also, you are measuring the volume and area of the mesh from RapidFormXOR, correct ? In that case, your surface area should be a little greater because your mesh has 1/2 the points of the cloud set I am processing which has triangular facets too but more of them. I'll run the RapidForm mesh cloud through my custom code and see what happens.
Yes, all measurements are the inbuilt querying tools in the software. The documentation does not discuss the methods used.
How much does RapidForm XOR cost ? I get the feeling it's expensive.
At least in the tens of thousands. A similar product we looked at as well was Geomagic. The Rhino3d modeling software I mentioned up thread retails for ~1k, but I am not sure of the measuring capabilities of that software. EDIT: a quick check shows it does measure volumes and surfaces. And they do a pretty good evaluation offer: http://download.rhino3d.com/rhino/4.0/e ... /download/
Have you had a look at Matlab (or it's open source equivalent, GNU Octave?) That sort of programming environment is made for hard core manipulation of large data sets. There is a fairly well known Matlab method for calculating the volume of a point cloud, but I have yet to track down details, other than it is the summation of the volumes of the set of tetrahedrons created by the tet faces and a central point. Actually pretty similar to what you are doing, but a 3d calculation, rather than a stack of 2d slices made from the area calculation of the triangles making up the slice.
Have a look at http://iso2mesh.sourceforge.net/cgi-bin/index.cgi?Home