How do I use a transform matrix to get a new matrix?

Question

Grant Sandy 2016-7-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/296168-how-do-i-use-a-transform-matrix-to-get-a-new-matrix

评论： Grant Sandy 2016-8-1

采纳的回答： Star Strider

在 MATLAB Online 中打开

If I generate a 3D cylinder using the cylinder function

[x,y,z]=cylinder(1,60);

I can rotate the surface object with handle-graphics

(makehgtform(..); % which displays in the surf() just fine.

I know that the tc.Matrix will supply a 4x4 transformation matrix which looks correct, but the dimensions of x,y,and z are 2x61. The x and y coordinates are two identical rows (of circles) and the z has one row for the bottom of the cylinder and one row for the top. Here is the problem: How do I use the generated 4x4 transform matrix to create a new matrix that has been transformed (rotated and translated) with the 6 rows of x,y,z?

R = makehgtform('xrotate',xRotation,...
                'yrotate',yRotation,...
                'zrotate',zRotation); 
S = makehgtform('translate',...
                [xTranslation, yTranslation, zTranslation]);
tc.Matrix = S*R;

I need the actual transformed vectors for analysis - not just the surf plot. I should be able to multiply

tc.Matrix * [x; y; z]

to obtain the new matrix but the multiple rows in x,y,z are problematic.

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Answer 1

Star Strider 2016-7-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/296168-how-do-i-use-a-transform-matrix-to-get-a-new-matrix#answer_228982

在 MATLAB Online 中打开

This uses the rotate function, not the ‘makehgtform’ functions, but it should demonstrate how to get the rotated and transformed data:

[x,y,z]=cylinder(1,60);
figure(1)
hcyl = surf(x,y,x);                         % Plot Cylinder
rotate(hcyl, [1 1 0], 25);                  % Rotate Cyulinder
hcylrot = get(hcyl);                        % Handle
xrot = hcylrot.XData;                       % Get Rotated Data

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Star Strider 2016-7-18

My pleasure!

It would help to see the relevant parts of your code. That way, I can experiment with it and probably provide a specific solution.

Grant Sandy 2016-8-1

Eventually, I created my own cylinder object with a meshgrid across the height (z) and the surface (theta). Then, I was able to rotate and translate the object and retrieve the Xdata, YData, and ZData like you recommended. The meshgrid was necessary because I need to find intersections between the cylinder and other objects of unknown geometry. Without meshgrid, I can't scan points along the height(z) to see if they are shared with the intersecting volumes. Now, my challenge is to create the same properties with a cube that contains a meshgrid on all 6 faces.

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