Rotate 3D object to align with x-y plane
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From: Marcin on 19 May 2010 02:20 Hi, I have a set of points describing a 3D object, which has been rotated by some small angle (below 45 degrees) with respect to x,y and z axis. I want to rotate it back to align it with the x-y plane, but the problem is I don't know the angles, so I need to calculate/estimate them somehow. So the questions are: 1. how to plot the object in a mesh like manner? 2. how to calculate the angles? 3. how to rotate it when I know the angles? Many thanks
From: Roger Stafford on 19 May 2010 18:45 "Marcin " <mb1234(a)gazeta.pl> wrote in message <hsvvv6$7rl$1(a)fred.mathworks.com>... > Hi, > > I have a set of points describing a 3D object, which has been rotated by some small angle (below 45 degrees) with respect to x,y and z axis. I want to rotate it back to align it with the x-y plane, but the problem is I don't know the angles, so I need to calculate/estimate them somehow. So the questions are: > > 1. how to plot the object in a mesh like manner? > 2. how to calculate the angles? > 3. how to rotate it when I know the angles? > > Many thanks I am not clear about what you mean when you say, "I want to rotate it back to align it with the x-y plane." Do the set of points "describing" the 3D object all lie in a plane? If so, there are many ways to rotate them so they all come to lie in the x-y plane. Any rotation axis which lies in the plane which bisects the dihedral angle between the points' plane and the x-y plane could be used. You can achieve any orientation you wish for the resulting x-y plane points. If you have a preferred final orientation for the points as they lie in the x-y plane, then I could give you a specific method for solving your problem. As it stands, the problem appears to be indeterminate if I have understood you correctly. Roger Stafford
From: Marcin on 20 May 2010 10:25 "Roger Stafford" <ellieandrogerxyzzy(a)mindspring.com.invalid> wrote in message <ht1pm2$1v$1(a)fred.mathworks.com>... > "Marcin " <mb1234(a)gazeta.pl> wrote in message <hsvvv6$7rl$1(a)fred.mathworks.com>... > > Hi, > > > > I have a set of points describing a 3D object, which has been rotated by some small angle (below 45 degrees) with respect to x,y and z axis. I want to rotate it back to align it with the x-y plane, but the problem is I don't know the angles, so I need to calculate/estimate them somehow. So the questions are: > > > > 1. how to plot the object in a mesh like manner? > > 2. how to calculate the angles? > > 3. how to rotate it when I know the angles? > > > > Many thanks > > I am not clear about what you mean when you say, "I want to rotate it back to align it with the x-y plane." Do the set of points "describing" the 3D object all lie in a plane? If so, there are many ways to rotate them so they all come to lie in the x-y plane. Any rotation axis which lies in the plane which bisects the dihedral angle between the points' plane and the x-y plane could be used. You can achieve any orientation you wish for the resulting x-y plane points. If you have a preferred final orientation for the points as they lie in the x-y plane, then I could give you a specific method for solving your problem. As it stands, the problem appears to be indeterminate if I have understood you correctly. > > Roger Stafford Hi Roger, Thanks for replying. I'll try to be more precise. I have a set of coordinates in 3 dimensions (xyz triplets), which describe some object. Due to the way the coordinates have been recorded, the object might be rotated, so that it's position is not say horizontal. I need to rotate it back, but first I need to detect the angle by which to rotate. Also, is there a nice way to plot the object in MATLAB? Is it possible to interpolate or convert the data somehow to use the patch function or surf maybe? Thanks
From: Matt J on 20 May 2010 11:06 "Marcin " <mb1234(a)gazeta.pl> wrote in message <ht3go0$6hi$1(a)fred.mathworks.com>... > "Roger Stafford" <ellieandrogerxyzzy(a)mindspring.com.invalid> wrote in message <ht1pm2$1v$1(a)fred.mathworks.com>... > > "Marcin " <mb1234(a)gazeta.pl> wrote in message <hsvvv6$7rl$1(a)fred.mathworks.com>... > > > Hi, > > > > > > I have a set of points describing a 3D object, which has been rotated by some small angle (below 45 degrees) with respect to x,y and z axis. I want to rotate it back to align it with the x-y plane, but the problem is I don't know the angles, so I need to calculate/estimate them somehow. So the questions are: > > > > > > 1. how to plot the object in a mesh like manner? > > > 2. how to calculate the angles? > > > 3. how to rotate it when I know the angles? > > > > > > Many thanks > > > > I am not clear about what you mean when you say, "I want to rotate it back to align it with the x-y plane." Do the set of points "describing" the 3D object all lie in a plane? If so, there are many ways to rotate them so they all come to lie in the x-y plane. Any rotation axis which lies in the plane which bisects the dihedral angle between the points' plane and the x-y plane could be used. You can achieve any orientation you wish for the resulting x-y plane points. If you have a preferred final orientation for the points as they lie in the x-y plane, then I could give you a specific method for solving your problem. As it stands, the problem appears to be indeterminate if I have understood you correctly. > > > > Roger Stafford > > Hi Roger, > > Thanks for replying. I'll try to be more precise. I have a set of coordinates in 3 dimensions (xyz triplets), which describe some object. Due to the way the coordinates have been recorded, the object might be rotated, so that it's position is not say horizontal. I need to rotate it back, but first I need to detect the angle by which to rotate. =============== The notion of "horizontal" is ambiguous for a 3D object. How are you measuring horizontality? Is a bottle "horizontal" when it is standing upright on its base (instead of tilted) or when it is lying on the floor with its long axis parallel to the ground? Also, even if I give you a rotation that restores the object to a horizontal position (whatever that is), you don't have enough information to reconstruct how the object was oriented with respect to the horizontal plane. That is, if the x-y plane is horizontal, then I can rotate the object around the z-axis and it will still be horizontal. Do you care about recovering this part of the initial orientation?
From: mat001 on 20 May 2010 11:19
"Marcin " <mb1234(a)gazeta.pl> wrote in message <hsvvv6$7rl$1(a)fred.mathworks.com>... > Hi, > > I have a set of points describing a 3D object, which has been rotated by some small angle (below 45 degrees) with respect to x,y and z axis. I want to rotate it back to align it with the x-y plane, but the problem is I don't know the angles, so I need to calculate/estimate them somehow. So the questions are: > > 1. how to plot the object in a mesh like manner? > 2. how to calculate the angles? > 3. how to rotate it when I know the angles? > > Many thanks Read 3d Visulization |