fooman wrote:Try http://www.cyi.ac.cy/system/files/MeshLab%20Documentation1.pdf for 3rd party documentation of Meshlab.
Edit: there is a bunch on presentations on 3d scanning, including the use of Meshlab at http://vcg.isti.cnr.it/~callieri/blendercourse.html. This may be of some interest.
M.W.Taylor wrote:Larry Tucei wrote:Wow, That is an amazing graft you created. It must take many hours to do such a detailed mapping. Way cool! Larry
I download my data from the Impulse200LR and MapStar encoder directly to a field PC through serial data cables. I average about 1,000 data points per hour. This map of the first 20 feet of Drury's trunk took me about 4 hours due to clutter around the tree. I had to move around a lot to find clear views and that took some time. To completely map the tree this way will probably take at least 10 more hours of field time. There is just so much surface area to map on this behemoth. This tree appears to be 16' diameter at 100' off the ground. It's a massive wall of wood.
fooman wrote:Hi Michael,
The laser scanner we use is not a Lidar scanner - it does not use a reference position to generate the point cloud. It provides self positioning data via reflective spots that are randomly positioned on the scanned object. Once these points are registered the laser beam is scanned across the object, much like a spray can, "painting" the scanning beam across the object. This generates reasonably high resolution data (sub-millimetric) very rapidly - maybe a million points in an hour or so. But not really suitable for a large tree.
Another scanner I came across used self positioning in the magnetic field as some sort of golbal reference, but it could not scan metallic objects, so wasn't much use for us.
I've just remembered that our inspection division used to scan the inside of delayed coker drums (large refinery vessels - maybe 20-30 m tall, 4-5 m in diameter) using a laser process - a rotating prism was used to scan a beam around the inside circumference of the vessel, while being dropped down the axis, to pick up cracking/bulging in the vessel wall.
I do think structured light scanning is a real possibility for large trees - all that is needed is a reference dimension (e.g. taped girth) or length between two features on the trunk, a method to project a light pattern (a large projector at night?), and two cameras recording the image at a known baseline plus the software. The guys at the company I referred to in my earlier post were just using normal cameras mounted on tripods a known distance apart. The resolution of a scanned tree would be lower than the smaller objects normally scanned (e.g. people) but I guess +/- 1 inch would be ok for volume, rather than +/- 1 mm?
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