I want to know how to plot the intersection of a 3D picture with a plane.

I want to know how to plot the intersection of a 3D picture with a plane.

For example, my matlab code is

x=-10:0.1:10;

y=x;

[x,y]=meshgrid(x,y);

z=1-5*x.^2+3*y.^2+7*x.*y+4*x-9*y;

mesh(x,y)

I want to look at the intersecting line with z=c or z=ax+by(c,a,b are constant)

what matlab code can implement?

Answer 1

[Star Strider]

I am not certain what you want.

Try these:

x=-10:0.1:10;
y=x;
[x,y]=meshgrid(x,y);
z=1-5*x.^2+3*y.^2+7*x.*y+4*x-9*y;

figure
c = 1;
mesh(x,y,z)
hold on
contour3(x,y,z, [c,c], 'LineWidth',2, 'Color','k')              % One Contour Level At ‘c’
hold off

figure
c = 20*x+15*y;
mesh(x,y,z)
hold on
plot3(x,y,c, 'LineWidth',2, 'Color','g')                        % Plane Defined By ‘c’
hold off

Experiment to get different results.

[seth wade]

Thank you！hhhh

[Star Strider]

As always, my pleasure!

[seth wade]

And i have a question, what's the meaning of [c,c] in counter3

[Star Strider]

That defines one level of the contour. See Contours at One Level (link) for details.