John Ferrell wrote: > How do you add/remove data points? If you mean, at the code-implementation level, it's simply a 3D Array representation, "Data[x,y,z]", and a point is added by storing a value at a particular element, e.g. Data[122,345,55] = 1. Remove by setting the element value = 0. Jim ----- Original Message ----- From: "John Ferrell" To: Sent: Thursday, November 06, 2003 6:03 PM Subject: Re: [OT:] Looking for algorithm... > How do you add/remove data points? > > John Ferrell > 6241 Phillippi Rd > Julian NC 27283 > Phone: (336)685-9606 > johnferrell@earthlink.net > Dixie Competition Products > NSRCA 479 AMA 4190 W8CCW > "My Competition is Not My Enemy" > > > ----- Original Message ----- > From: "Jim Tellier" > To: > Sent: Thursday, November 06, 2003 7:42 PM > Subject: Re: [OT:] Looking for algorithm... > > > > David Minkler wrote: > > > What's fast? Do you have equations which describe the surface? Do you > > > need a one time solution or is this going to be done repeatedly? > > Dave, good question: I should have explained that a bit, actually. I > > *think* that the true value computation can be O(n) (i.e. linear) where > 'n' > > is the number of loci describing the hull. I'm not completely sure about > > that, but that's what I'm assuming is the case. Of course I'd like the > > approximation to require 0 time :^), but realistically if I found one that > > was 20% the cost of the true value comp, I'd be very happy. > > I don't have equations, just data points in 3D space; I can vary the > > "resolution" of the hull description quite easily - i.e., just generate > > fewer data points, which will obviously save time for any algorithm, but > > introduce error at the same time. > > This isn't a 1-time thing, it's part of a larger algorithm that will > need > > to invoke the approximation at a pretty high frequency (no, not in real > > time, thank goodness!) > > Jim > > > > > OP: > > > Jim Tellier wrote: > > > > Any math wizards here? I've been searching for quite a while now, but > > coming up empty ... I'm looking for an APPROXIMATION algorithm to compute > > the surface area of a convex hull shape. Given a 3D matrix (may be either > > sparse or complete, but would be best if I could use sparse to save space) > > of surface loci, I need a "reasonably accurate" (say +/- 15-20% variance > > from actual true value) but *fast* approximation. Parallel or > distributed > > algorithms would be ideal, but not a requirement. 3D geometry was never > > really in my bag o' tricks :^) > > > > Thanks for any suggestions or pointers! > > > > Jim > > > > > > -- > > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body