How do I create a 3 dimensional surface from X Y Z points

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Eric Verheyen
Eric Verheyen on 9 Mar 2018
Answered: Al Danial on 20 May 2022
Hi all,
I am struggling a bit here, and hope somebody could help. I have a set of points from a complex function that I am trying to produce a 3D shape of, and have had no luck so far. I used Python to find the points in a .txt format. From there, I copy the data to Excel to transpose the columns into rows for Matlab use. The problem is, I can't seem to figure out a code to just take the X, Y, and Z coordinates and produce some kind of mesh grid or figure. Does anybody have a code for this?
Here is an example of just (10) points from my function. I can tell Python to produce anywhere from 10 to 10,000 points.
x = [422 424 424 422 422 421 421 425 421 424]; y = [87 96 87 87 83 93 85 88 86 91]; z = [92.73 94.88 92.92 92.73 92.04 93.92 92.24 93.23 92.42 93.78];
Best regards,
Eric.

Answers (3)

Star Strider
Star Strider on 9 Mar 2018
Using the griddata (link) function is an option:
x = [422 424 424 422 422 421 421 425 421 424];
y = [87 96 87 87 83 93 85 88 86 91];
z = [92.73 94.88 92.92 92.73 92.04 93.92 92.24 93.23 92.42 93.78];
figure(1)
stem3(x, y, z)
grid on
xv = linspace(min(x), max(x), 20);
yv = linspace(min(y), max(y), 20);
[X,Y] = meshgrid(xv, yv);
Z = griddata(x,y,z,X,Y);
figure(2)
surf(X, Y, Z);
grid on
set(gca, 'ZLim',[0 100])
shading interp
Experiment to get the result you want.
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Shivam Anand
Shivam Anand on 11 May 2022
x=[32 20 67 1 98 34 57 65 24 82 47 55 8 51 13 14 18 30 37 39 10 33 21 26 38 81 83 60 95 22 17 5 72 46 99 52 12 25 96 29 70 85 43 69 19 78 97 31 89 53 2 91 48 71 61 15 36 84 94 50 11 80 6 7 49 74 9 88 40 79 27 68 73 64 63 59 86 23 35 58 45 28 100 42 93 87 16 90 41 66 54 92 77 4 62 76 75 56 3 44];
y=[96 75 24 9 83 49 27 77 3 23 17 31 40 13 7 52 51 21 98 47 64 79 78 91 44 16 15 100 84 99 63 68 70 30 54 76 97 73 33 5 88 8 71 66 62 25 60 42 72 45 18 11 28 59 89 65 10 55 69 81 12 26 20 95 87 41 74 50 93 22 43 90 14 34 82 35 56 38 80 32 1 57 6 36 37 61 29 58 2 48 4 46 67 53 92 86 94 19 39 85];
z=[55 31 11 45 83 36 86 49 15 57 42 46 8 94 88 47 54 81 98 41 32 35 56 85 9 89 37 60 23 62 67 100 78 76 73 80 10 20 68 34 77 93 1 63 53 12 22 99 91 40 84 24 33 3 43 19 92 97 6 82 64 25 26 79 95 4 44 58 5 21 70 29 65 87 96 90 51 14 18 2 72 28 71 39 52 7 27 59 50 61 48 30 66 69 17 13 74 16 75 38];
xlin = linspace(min(x), max(x), 100);
ylin = linspace(min(y), max(y), 100);
[X,Y] = meshgrid(xlin, ylin);
% Z = griddata(x,y,z,X,Y,'natural');
% Z = griddata(x,y,z,X,Y,'cubic');
Z = griddata(x,y,z,X,Y,'v4');
mesh(X,Y,Z)
axis tight; hold on
plot3(x,y,z,'.','MarkerSize',15)

Al Danial
Al Danial on 20 May 2022
Since you're starting in Python you can make the surface plot there too if you want. This is a translation of @Star Strider's matlab solution:
#!/usr/bin/env python
import matplotlib.pyplot as plt
from matplotlib import cm
import numpy as np
from scipy.interpolate import griddata
x = np.array([422, 424, 424, 422, 422, 421, 421, 425,
421, 424])
y = np.array([87, 96, 87, 87, 83, 93, 85, 88, 86, 91])
z = np.array([92.73, 94.88, 92.92, 92.73, 92.04, 93.92,
92.24, 93.23, 92.42, 93.78])
xv = np.linspace(np.min(x), np.max(x), 20)
yv = np.linspace(np.min(y), np.max(y), 20)
[X,Y] = np.meshgrid(xv, yv)
Z = griddata((x,y),z,(X,Y),method='linear')
fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
surf = ax.plot_surface(X, Y, Z, cmap=cm.coolwarm,
linewidth=0, antialiased=False)
ax.set_xlabel('X')
ax.set_ylabel('Y')
fig.colorbar(surf, shrink=0.6)
plt.show()

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