surface data representation (triangulation...?)

Dear all, after searching by myself for a couple of days I allow myself to post a question. How do i plot a colored surface in 3d space, given the data points as (x,y,z, property)? The points clearly lie on a surface, but the shape is non-trivial and non-convex.

the best i got is using scatter3, but this is clearly not what I am looking for:

 clc
 clear all
 close all
 load('datafile.mat');
 n=1; %only load every nth point for better performance
 x=      data(1:n:end,1);
 y=      data(1:n:end,2);
 z=      data(1:n:end,3);
 prop=   data(1:n:end,4);

 %plot all data
 figure(1)
 scatter3(x,y,z,2,prop)

 %plot only one quadrant for better visibility
 xx=x(and(x>0,y>0))
 yy=y(and(x>0,y>0))
 zz=z(and(x>0,y>0))
 pp=prop(and(x>0,y>0))
 figure(2)
 scatter3(xx,yy,zz,2,pp)

giving

What i tried before is delaunay triangulation, freesurface and convexhull. I could not find something that would return a list of triangles rather than tetraeders. i thought about deviding this surface into fractions that can be seen as function z=f(x,y) and apply the 2d-triagnulation. but this is tideous and not straight forward.

thanks for any suggestions! best, martin

Answer 1

[Mike Garrity]

The new alphashape command does a pretty good job with this. Here's what I get with the defaults:

shp=alphaShape(x,y,z);
plot(shp,'EdgeColor','none');
camlight
axis normal

You might be able to do better by adjusting some of the parameters.

[martin]

ill have to upgrade to 2014b first, currently running 2014a. but thanks anyway for this! ill com back to it soon