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Game Development / Newbie & Debugging Questions / Re: 3D triangle generation from list of points

on: 20080701 13:33:38

I have a routine in Java3D that will let normalize and let me rotate the surface plot, so this isnt a problem.
We have attacked some problems before like this, and we currently export the data, and import into a 3rd party application, which is a pain. The "object" is just a surface  imaging banging nails into a block of wood, to various depths, and then dropping a thin cloth over the top  this is all I'm trying to visualize.
Based on what Ive read, I think the Delaunay algorithm in 2D is the way to go (the Convex Hull algo closes off the surface, thus making a solid which isn't what Im after). However, although it seems that every geometry researcher on the face of the planet has written a Delaunay Java applet, none of the source works out of the box for what we want to do (which doesnt seem to be too far out there), so I'm currently chopping at one I found that looks promising, but even that one starts with a massive starting triangle, and then plots all the points inside that triangle  which just introduces additional triangles and edges that are not relevant.
The model that is under inspection is very complex, and if I could do this in an analytical manner, I would  however, the number of variables in the model, and the time it takes to execute the model is prohibitive hence why I want to plot it in 3D. Ive already done this for some 2D problems, and it was very effective.



3

Game Development / Newbie & Debugging Questions / Re: 3D triangle generation from list of points

on: 20080630 15:24:21

Many thanks for all the suggestions.
Ok, so Ive already looked at the Convex Hull stuff (since it was referenced from many of the Delaunay papers and web pages I looked at).
What I'm unsure of is if the Convex Hull will generate the triangles for the surface, or if it will "close" the surface thus making a 3D object (which isnt what Im looking to display). Im trying to build a 3D surface plot of some arbitrary data (Im looking for spikes in some function ouput). Each routine takes many minutes to run (its complex). While trying to make the function smooth, I am varying various input params. Id like to graph the output in real time, such that if I see a spike in the graph, I can kill the test, and try something else  I dont want to have to wait 20 mins just to find out that the function output still isnt smooth.
My understanding of this problem are based on the following: 1.) I need to generate triangles (or quads) from my point cloud so that I can get Java3D (or whatever) to draw these. I spent several hours looking at Delaunay algorithms to figure out my triangles  how is this different than computing the convex hull?
2.) If my data was on a known XY grid, life would be much easier.
Ive looked at the Convex Hull. Now Im a little confused  the convex hull seems to give me the outer boundary  does it also give me the triangles that make up the surface, or do I need to use the Delaunay algorithm for that?
Thanks for the help.



4

Game Development / Newbie & Debugging Questions / 3D triangle generation from list of points

on: 20080629 20:47:25

I'm trying to display a 3D surface based on an arbitrary list of 3D points (kind of like having the points in 3D space, then dropping a blanket down from the Z direction such that the surface lies on top of all the points). No holes or anything like that  I just want to view how the surface looks.
Although this would seem like a very common thing, Ive not found anything in Java 3D or JOGl to just take these points and display it.
Is there a way to do this easily in Java 3D and/or JOGL?
Do I have to convert these points into triangles (in a 3D space) in order to display the surface using one of the many algorithms out there (Delaunay etc.)? If so, is there a point cloud > triangle mesh algorithm built in to Java 3D and/or JOGL, or do you know of a Java implementation of one?
Any pointers/suggestions appreciated.





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