How to plot a line of zero value on a surface?

Question

Ying Wu 2022-12-13

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877487-how-to-plot-a-line-of-zero-value-on-a-surface

评论： Star Strider 2022-12-13

采纳的回答： Star Strider

Y.mat
Z.mat

在 MATLAB Online 中打开

I used surf to generate a 3D surface and see it in 2D view (see below)

The dataset and code are also attached.

X=[0 0.25 0.5 0.75]';  % 4*1 vector
load Y.mat             % 36*4 matrix
load Z.mat             % 36*4 matrix
figure
set(gcf,'position',[100,100,1000,750]);
surf(X, Y, Z, 'EdgeColor', 'none', 'FaceColor', 'interp');
hold on;
colormap(coolwarm(256)); caxis([-0.35 0.35]); colorbar; 
patch([0,0.8,0.8,0],[0.8,0.8,0,0],[0,0,0,0],[1,1,1,1],'FaceAlpha',0.5,'EdgeColor',[0,0,0]);
grid off; view(2);

Now I want to plot the intersection of surface and zero-plane, can anyone help to with that? Thanks!

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Answer 1

Star Strider 2022-12-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877487-how-to-plot-a-line-of-zero-value-on-a-surface#answer_1127247

在 MATLAB Online 中打开

Use contour3 to draw the boundary (here a red line with 'LineWidth',5) —

LD1 = load(websave('Y','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1230092/Y.mat'));

Y = LD1.Amp;

LD2 = load(websave('Z','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1230097/Z.mat'));

Z = LD2.Pnet;

X=(ones(size(Z,1),1)*[0 0.25 0.5 0.75]);

% 4*1 vector

% load Y.mat % 36*4 matrix

% load Z.mat % 36*4 matrix

figure

set(gcf,'position',[100,100,1000,750]);

surf(X, Y, Z, 'EdgeColor', 'none', 'FaceColor', 'interp');

hold on;

colormap(turbo(256)); caxis([-0.35 0.35]); colorbar;

patch([0,0.8,0.8,0],[0.8,0.8,0,0],[0,0,0,0],[1,1,1,1],'FaceAlpha',0.5,'EdgeColor',[0,0,0]);

contour3(X, Y, Z, [0 0], '-r', 'LineWidth',5)

grid off

view(-160,30)

% view(2);

The plane at ‘Z=0’ partially obscures the line.

.

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Star Strider 2022-12-13

在 MATLAB Online 中打开

Not if you want it exactly at zero.

One option —

LD1 = load(websave('Y','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1230092/Y.mat'));

Y = LD1.Amp;

LD2 = load(websave('Z','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1230097/Z.mat'));

Z = LD2.Pnet;

X=(ones(size(Z,1),1)*[0 0.25 0.5 0.75]);

% 4*1 vector

% load Y.mat % 36*4 matrix

% load Z.mat % 36*4 matrix

figure

set(gcf,'position',[100,100,1000,750]);

surf(X, Y, Z, 'EdgeColor', 'none', 'FaceColor', 'interp');

hold on;

colormap(turbo(256)); caxis([-0.35 0.35]); colorbar;

patch([0,0.8,0.8,0],[0.8,0.8,0,0],[0,0,0,0],[1,1,1,1],'FaceAlpha',0.5,'EdgeColor',[0,0,0]);

contour3(X, Y, Z, [0 0.005], '-r', 'LineWidth',5)

grid off

% view(-160,30)

view(2);

figure

set(gcf,'position',[100,100,1000,750]);

surf(X, Y, Z, 'EdgeColor', 'none', 'FaceColor', 'interp');

hold on;

colormap(turbo(256)); caxis([-0.35 0.35]); colorbar;

patch([0,0.8,0.8,0],[0.8,0.8,0,0],[0,0,0,0],[1,1,1,1],'FaceAlpha',0.5,'EdgeColor',[0,0,0]);

contour3(X, Y, Z, [0 0], '-r', 'LineWidth',15)

grid off

% view(-160,30)

view(2);

This draws two contours, one at 0 and the other at 0.005. You can adjust one or both of those values as necessary to get the result you want. For example [1 1]*0.005 would draw one contour at 0.005. There must always be at least two elements to a vector fixing a contour level.

Another option (second figure) is just to thicken the line.

Providing higher resolution data could also work to make the line more easily visible, since this would reduce the need for contour3 to interpolate the level.

Still another option would be to nudge the zero-plane slightly lower so that it doesn’t hide the contour line.

.

Ying Wu 2022-12-13

Thanks for detailed reply!

Star Strider 2022-12-13

As always, my pleasure!

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How to plot a line of zero value on a surface?

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