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Subject:	OK here's the real problem! (Was: Re: Finding a rotation matrix for a triangle)
Newsgroups:	lugnet.cad
Date:	Tue, 6 Dec 2005 16:37:45 GMT
Viewed:	1932 times

Well, I think I’ve tried to explain what I need to do 3-4 times already, which is where I think the language barriers have played a pretty big role...

The reason I tried to cook the problem down, is to reduce confusion, but I guess that was a bad idea if my ideas went in the wrong direction ;-)

Regarding the formula you suggested, I’m afraid that I can’t use it: I can’t just add the primitive via text, because I need to turn it around the y-axis before I get to the problem I posted about here. And although possible, scaling afterwards would be difficult.

I think I need to adopt a more direct approach, so I’ll try to explain excactly what I need to do:

1 14 -30 4 10 0 0 1 0 -5 0 -1 0 0 stud3.dat
4 4 -24 4 -16 -24 20 -46 -36 20 -10 -36 4 20
2 2 -36 4 20 -24 4 -16
1 2 -30 4 10 -3.69552 0 -1.53073 0 1 0 1.53073 0 -3.69552 1-4edge.dat

I have this stud3 that passes through the wonky quad (line 1 and 2). I need an edge between the two of them, and want to use the 1-4edge for that (line4).

Note that I’ve already scaled and turned the edge 22.5 degrees around the y axis.

What I need now, is to turn the edge down at the same angle as the surface of the quad, and since I don’t want to loose the previous two steps (scaling and first angling), I have to do it via the rotation vector command in MLCAD “on top” of them.

As far as I can see, what you’re suggesting is simply to enter a new rotation matrix via notepad, but that will of course delete the two other nessecary steps, unless you use a much more complex formula that includes the effect of all three steps.

I hope that it’s more clear now, and that I got some of the worms back inside the can...

Cheers NB

Message has 3 Replies:

		Re: OK here's the real problem! (Was: Re: Finding a rotation matrix for a triangle)
(...) I think my interpratation from the last time was halfway there and this explains it much better so we're definitely getting somewhere faster now :). You should be able to use the formula I gave in the last reply instead of an XYZ+angle in (...) (19 years ago, 6-Dec-05, to lugnet.cad, FTX)

		Re: OK here's the real problem! (Was: Re: Finding a rotation matrix for a triangle) [DAT]
(...) Take the edge line: 1 2 -30 4 10 -3.69552 0 -1.53073 0 1 0 1.53073 0 -3.69552 1-4edge.dat Put it in a separate subfile. Include that subfile with no rotation matrix. Now apply a new MLCad rotation to the subfile. Finally inline the subfile to (...) (19 years ago, 6-Dec-05, to lugnet.cad, FTX)

		Re: OK here's the real problem! (Was: Re: Finding a rotation matrix for a triangle)
(...) Actually, what you need to do is skew the 1-4edge. Literally deform it, so it stretches along the edge of the stud3 cylinder. If you turn it, it will no longer intersect the surface of the cylinder -- the edge will disappear inside the (...) (19 years ago, 6-Dec-05, to lugnet.cad, FTX)

Message is in Reply To:

		Re: Finding a rotation matrix for a triangle
(...) Now I think I see what you mean. You want to know how to rotate the primitive so that it lines up with one of the edge lines of the triangle. (...) This isn't the best way to go (I'll explain at the end of the post). (...) OK. The problem here (...) (19 years ago, 5-Dec-05, to lugnet.cad)

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