 | | 3D geometry question —Fredrik Glöckner
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| | | Hi, I have this problem I hope someone may solve. Say I have a vector v with length normalized to 1. For simplicity, picture this vector as starting in the origin. Now, I need a rotation matrix M with the following properties: o If I rotate a part (...) (25 years ago, 13-Oct-99, to lugnet.cad)
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| | | | | Re: 3D geometry question —Jacob Sparre Andersen
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| | | | | Fredrik Glöckner: (...) Vectors don't start anywhere. A vector is just a direction and a length. (...) Lets call the vector along the edge e. (...) There are infinitely many solutions to the problem. When you have one solution, any rotation around v (...) (25 years ago, 13-Oct-99, to lugnet.cad)
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| | | | | | | Re: 3D geometry question —Fredrik Glöckner
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| | | | | | (...) Sure. But to picture the vector as starting in the origin makes it easier to understand what I want in the paragraph below: (...) In fact, for my application, any of these solutions would suffice. (...) I think we also need some constraints on (...) (25 years ago, 13-Oct-99, to lugnet.cad)
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| | | | | Re: 3D geometry question —Anders Isaksson
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| | | | Fredrik Glöckner skrev i meddelandet ... (...) What about: Assume V = (Vx, Vy, Vz) B = arctan(Vx/Vz) (Better with arctan2(Vz, Vx) if available, otherwise you have to adjust to the right quadrant manually) Matrix for rotation around Y: ( cos(B) 0 (...) (25 years ago, 13-Oct-99, to lugnet.cad)
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| | | | | | Re: 3D geometry question —Anders Isaksson
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| | | | Sorry, I just found out that I solved for (0,0,-1), not (0,-1,0), but that's just a symmetry change :-)) -- Anders Isaksson, Sweden BlockCAD: (2 URLs) (25 years ago, 13-Oct-99, to lugnet.cad)
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| | | | | | Re: 3D geometry question —Fredrik Glöckner
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| | | | Thanks for all the help and suggestions. However, I found an alternate way of doing this last night. The columns in M are simply the axis spanning the rotated coordinate system, right? So we can use v as the 2nd axis to get the v vector pointing (...) (25 years ago, 14-Oct-99, to lugnet.cad)
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| | | | | | Re: 3D geometry question —Jacob Sparre Andersen
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| | | | Fredrik: (...) [ ... ] Nice solution. :) I should have thought of it. :( Play well, Jacob ---...--- -- E-mail: sparre@cats.nbi.dk -- -- Web...: <URL:(URL) -- ---...--- (25 years ago, 26-Oct-99, to lugnet.cad)
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