Problem with data triangulation

Dear Matlab users,

I am trying to visualize a surface made of 3d scattered points. It is not an F(x,y) -> z function, z is just a scalar associated to (x,y) pairs. The x and y pairs form a fairly uniform rectangular grid on the xy plane. However, as soon as I try to use trisurf, the data are triangulated in an unexpected fashion.

I am actually interested in "connecting" these 3d points, not in an interpolation. The surface which can be glimpsed from scatter3 appears to be quite regular, but I wasn't succesfull in using trisurf or even surf.

Can you help me in achieving this goal? I am probably missing something in how the delaunay triangulation works.

Thank you in advance,

Leonardo

Answer 1

[darova]

It's because of different scales

try to scale your data

dx = max(x)-min(x);
y1 = (y-min(y))/(max(y)-min(y))*dx;
T = delaunay(x,y1);
trisurf(T, x, y, z)
axis vis3d

Answer 2

[Ameer Hamza]

If you want to visualize the data as surface, then you can first use griddata() to make it into a grid and then use surf()

x = [-108.743 -108.734 -108.71 -108.699 -108.684 -108.674 -108.664 -108.656 -108.651 -108.647 -108.645 -107.259 -107.216 -107.179 -107.148 -107.123 -107.123 -107.105 -107.104 -107.094 -107.093 -107.09 -105.784 -105.731 -105.683 -105.641 -105.605 -105.574 -105.55 -105.533 -105.523 -105.522 -105.519 -104.318 -104.255 -104.197 -104.144 -104.096 -104.054 -104.017 -103.986 -103.962 -103.944 -103.932 -102.862 -102.789 -102.721 -102.657 -102.598 -102.543 -102.494 -102.45 -102.412 -102.379 -102.353 -101.416 -101.334 -101.255 -101.18 -101.11 -101.044 -100.982 -100.925 -100.873 -100.826 -100.784 -99.981 -99.889 -99.8 -99.715 -99.633 -99.555 -99.481 -99.411 -99.346 -99.284 -99.228 -98.557 -98.455 -98.357 -98.261 -98.168 -98.078 -97.992 -97.909 -97.83 -97.755 -97.684 -97.144 -97.033 -96.924 -96.818 -96.715 -96.613 -96.515 -96.42 -96.327 -96.238 -96.152 -95.743 -95.623 -95.504 -95.388 -95.273 -95.161 -95.051 -94.943 -94.837 -94.733 -94.633 -94.353 -94.224 -94.096 -93.97 -93.845 -93.721 -93.599 -93.478 -93.359 -93.242 -93.127]
y = [0.034 -0.003 0.031 0.0 0.027 0.004 0.023 0.008 0.02 0.012 0.016 0.035 0.031 0.028 0.024 -0.003 0.02 0.016 0.001 0.013 0.005 0.009 0.036 0.032 0.028 0.025 0.021 0.017 0.013 0.01 -0.002 0.006 0.002 0.037 0.033 0.029 0.026 0.022 0.018 0.014 0.01 0.007 0.003 -0.001 0.037 0.034 0.03 0.026 0.023 0.019 0.015 0.011 0.007 0.003 -0.0 0.038 0.035 0.031 0.027 0.023 0.02 0.016 0.012 0.008 0.004 0.0 0.039 0.035 0.032 0.028 0.024 0.02 0.017 0.013 0.009 0.005 0.001 0.04 0.036 0.032 0.029 0.025 0.021 0.017 0.014 0.01 0.006 0.002 0.041 0.037 0.033 0.03 0.026 0.022 0.018 0.014 0.011 0.007 0.003 0.041 0.038 0.034 0.03 0.027 0.023 0.019 0.015 0.011 0.008 0.004 0.042 0.039 0.035 0.031 0.028 0.024 0.02 0.016 0.012 0.008 0.005]
z = [-868.98181753 -869.03656771 -869.00509484 -869.04789749 -869.02312937 -869.05456316 -869.03633374 -869.05691311 -869.04545933 -869.05571162 -869.0516303 -868.9851162 -869.00814308 -869.02572477 -869.03837956 -869.03783079 -869.04690268 -869.052603 -869.04921017 -869.05666944 -869.05589316 -869.05819117 -868.98833862 -869.01094443 -869.02795695 -869.04004859 -869.04791168 -869.05300034 -869.0571638 -869.05889077 -869.03849659 -869.05665363 -869.04993744 -868.99135258 -869.0134021 -869.02987311 -869.04137699 -869.04853356 -869.05287429 -869.05733 -869.05927447 -869.05702861 -869.05025941 -869.0387455 -868.99418691 -869.01558818 -869.0314407 -869.04237632 -869.04885431 -869.05217803 -869.05732872 -869.05940833 -869.05710197 -869.05022895 -869.03861199 -868.99666945 -869.01737986 -869.03274665 -869.04315341 -869.04910188 -869.05094408 -869.05733703 -869.05931497 -869.05685168 -869.04983308 -869.03810889 -868.99897704 -869.01895679 -869.03367205 -869.04362787 -869.04933318 -869.05243749 -869.05738309 -869.05890597 -869.05626901 -869.04905847 -869.03722417 -869.00101379 -869.02022918 -869.03437482 -869.04397026 -869.04968638 -869.05350931 -869.05745965 -869.05847175 -869.05539754 -869.04787576 -869.03585189 -869.00273423 -869.0211671 -869.03476459 -869.04409116 -869.04993815 -869.05406865 -869.05730611 -869.05770149 -869.05423116 -869.04651483 -869.03430857 -869.0041773 -869.0217949 -869.03486759 -869.04393834 -869.04990448 -869.05411243 -869.05676928 -869.05659592 -869.05271983 -869.04471149 -869.03232427 -869.00529229 -869.02209147 -869.03464015 -869.04350052 -869.04951656 -869.05362124 -869.05579053 -869.05509436 -869.05082327 -869.04252703 -869.02988852]

xg = linspace(min(x), max(x), 100);
yg = linspace(min(y), max(y), 100);
[Xg, Yg] = meshgrid(xg, yg);
Zg = griddata(x, y, z, Xg, Yg);
s = surf(Xg, Yg, Zg);

[LEONARDO BARNESCHI]

Dear Ameer,

the problem is that I should be able to just connect properly the 3d points. In a sense, they should be connected according to the distance on the xy plane. The surface or "trisurface" should be regular. I can get something like this using interpolation, but I was wondering if I could just work on the connectivity.

Thank you,

Leonardo