3D plotted shape is not following curvature of data points

Question

Sumeet Chaudhari 2020-7-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/560450-3d-plotted-shape-is-not-following-curvature-of-data-points

编辑： John D'Errico 2020-7-6

seg_info.mat

I am writing a code that creates a 3D shape from a set of data points and am running into this problem where the shape does not properly follow the curvature of the data points and rather draws a straight line. This can be seen on the sides of the figure below where the shape isn't properly following the data points into the curves.

My code:

load('seg_info.mat');
x = seg_info(:, 1);
y = seg_info(:, 2);
z = seg_info(:, 3);
colors = seg_info(:, 4);
scatter3(x,y,z);
hold on;
DT = delaunayTriangulation(x, y, z);
[K, v] = convexHull(DT);
trisurf(K, DT.Points(:,1), DT.Points(:,2), DT.Points(:,3), ...
	'FaceAlpha', 0.5, 'EdgeColor', 'none', ...
	'CData', colors, 'FaceColor', 'interp');

Does anyone know how I can improve my code to better fit these sides? I have tried using alpha shapes and boundary in an attempt to derive the concave hull but neither worked.

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John D'Errico 2020-7-6

You think the problem is in the triangulation? A delaunay triangulation trinagulates the entire region within the convex hull of the data. In fact, you even used a convex hull there. So surely you would expect that the result will be a convex region. If you don't want it to be convex, then you can't use a convex hull. Or for that matter, a Delaunay triangulation.

Sumeet Chaudhari 2020-7-6

I have been trying to use mesh and even searching File Exchange for a program that calculates a concave hull. Looking at a scatter3 plot, I wish there was a way to just connect all the dots since the input data already represents the outer surface of the shape.

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