matlab - Matlab Delaunay Triangulation of Point Cloud - Color Matrix

Question

I would like to create a plot of the 3D surface that spans over all points from an [X,Y,Z] point cloud. For example this is a scatter plot of my point cloud:

scatter3(X,Y,Z,5,C)

As you can see each data point has an intensity value C.

I now carry out the triangulation

dt      = DelaunayTri(X,Y,Z); 
[tri Xb]= freeBoundary(dt); 

And I get the triangulated surface

figure 
trisurf(tri,Xb(:,1),Xb(:,2),Xb(:,3), 'FaceColor', 'cyan', 'faceAlpha', 0.8);

However, when I try to set the colour of the surface using

trisurf(tri,Xb(:,1),Xb(:,2),Xb(:,3),C,'EdgeAlpha',0,'FaceColor','interp')

I get the error message: "Warning: Color Data is not set for Interpolated shading", which is due to the fact that the size of C does not match Xb or tri.

How can I make sure I get the correct interpolated surface colour?

Answer 1

您通过调用 freeBoundary 更改了绘制的三角剖分中的点数：只剩下表面点，内部点不属于表面。因此，您必须提取对应于这些点的 C 值。您可以使用 'intersect(..., 'rows')' 将曲面点 Xb 映射到原始点集 XYZ。根据此映射，您可以从 C 中提取所需的值。下面的代码执行此操作。

clear all;

XYZ = rand(100,3);
X=XYZ(:,1);
Y=XYZ(:,2);
Z=XYZ(:,3);
C=rand(size(X));

scatter3(X, Y, Z, 5,C);

dt = DelaunayTri(X, Y, Z);
[tri Xb]=freeBoundary(dt);

% map Xb onto XYZ
[~,IA,IB]=intersect(XYZ, Xb, 'rows');

% extract the needed colors using the IA map
Cn      = C(IA);

% permute the surface triangulation points using IB map
Xbn     = Xb(IB,:);

% map the point numbers used in triangle definitions
% NOTE: for that you need inverse map
iIB(IB) = 1:length(IB);
trin    = iIB(tri);

trisurf(trin,Xbn(:,1),Xbn(:,2),Xbn(:,3),Cn,'EdgeAlpha',0,'FaceColor','interp');