why point correspondence to rotation matrix calculation is not my expected?

6 次查看（过去 30 天）

cui,xingxing 2022-5-11

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1716235-why-point-correspondence-to-rotation-matrix-calculation-is-not-my-expected

评论： cui,xingxing 2022-10-10

for example, at first ,one point P1(1,0,0) rotate pi/2 angle by y-axis,then get the point P2(0,0,-1), then rotate pi/2 angle by x-axis, then get the point P3(0,1,0). i use eul2rotm function to specify eular angle to get rotation matrix,then get the destination point by premultipy format,but get the result is not my expected P3?

P1 = [1,0,0]; 
eular = [0,pi/2,pi/2]
eular = 1×3
         0    1.5708    1.5708
r = eul2rotm(eular,'ZYX'); % premultipy format
destinationPt = r*P1' % not same as P3 ?
destinationPt = 3×1
    0.0000
         0
   -1.0000

if i take eular decompose into two component, ie rotate pi/2 angle correspondance to y-axis,x-axis, then i can get my expected result P3.

eularY = [0,pi/2,0];
eularX = [0,0,pi/2];
ry = eul2rotm(eularY);
rx = eul2rotm(eularX);
destiPt = rx*ry*P1' % is same as P3, which is my expect result.
destiPt = 3×1
    0.0000
    1.0000
   -0.0000

i don't understand why eular angles vector three components not write together?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Matt J 2022-5-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1716235-why-point-correspondence-to-rotation-matrix-calculation-is-not-my-expected#answer_961530

编辑：Matt J 2022-5-11

r needs to be pre-multiplied by P1, not post-multiplied.

P1 = [1,0,0]; 
eular = [0,pi/2,pi/2];
r = eul2rotm(eular,'ZYX'); 
destinationPt = P1*r 
destinationPt = 1×3
    0.0000    1.0000    0.0000

12 个评论
显示 10更早的评论隐藏 10更早的评论

Matt J 2022-5-11

Great!

cui,xingxing 2022-10-10

It is good to hear that since R2022b, the computer vision toolbox and image process toolbox have started to support the use of the pre-multiply convention as a priority，while the default for other toolkboxs is the pre-multiply convention remains unchanged.

请先登录，再进行评论。