angles math help

 From: BurrMan 25 Jul 2014  (1 of 14)
 I would like to ask for help on a method to derive a desired angle. I would like to have the angle to cut the bottom of this cylinder so that it can be placed flat and have it angled 60 degrees to the side and 15 degrees forward.. In this file I rotated the cylinder 60 to the side then 15 forward and cut it off to reveal the angle, however I realized that after I made the second rotation, this changed the first 60 angle I made.... Can anyone help me with a method/formula to end up with the angle cut I need to generate a 60/15 here? Much appreciated... file attached. Attachments:

 From: Dan (MONTAGMAN) 25 Jul 2014  (2 of 14)
 6835.2 In reply to 6835.1 I made this nice model to address your problem and then remembered that my trial expired (still waiting on v3 to buy), so all I can give you is an image and a description. Anyway, if I understand your question right, you want the cylinder to make a 15 degree angle projected onto the top view, and a 60 degree angle projected onto the front view. You're right that you can't do this with two rotations unless you do some math first to figure out the proper rotation angles. But, it can be done without math if you draw the cylinder last. First, draw lines in the top and front view with the desired angles. Then, extrude them both and get the intersection line between the two resulting surfaces. Next, create a c-plane aligned to this line, making sure that the z-axis is parallel to the intersection line. Finally, draw a circle on this c-plane and extrude it along the z-axis. Then you can cut it using a surface on the world x-y plane. Hopefully that makes sense. In the attached image, the red lines and planes are the construction pieces I used to get the proper intersection line, and the gray plane is the cutting plane. Sorry I couldn't provide a 3dm file, and hopefully this is the kind of result you're shooting for. Dan Image Attachments:

 From: Frenchy Pilou (PILOU) 25 Jul 2014  (3 of 14)
 And make rotate 60 then 15 of a cutting plane is not sufficient without move the cylinder?

 From: BurrMan 25 Jul 2014  (4 of 14)
 6835.4 In reply to 6835.2 Ahh, the ole intersection line from 2 angled planes trick!!! That sounds like it may be the answer. any other comments to confirm welcomed.... Thanks Dan....

 From: Michael Gibson 25 Jul 2014  (5 of 14)
 6835.5 In reply to 6835.4 Hi Burr yeah I agree with Dan's method - since you're interested in the projected angle in each view it's easier to get the axis line you want by the intersection of 2 extrusions rather than doing rotations. It's definitely true that if you rotate a line in the top view, it will change the angle of the line as viewed in the the front view. - Michael

 From: Michael Gibson 25 Jul 2014  (6 of 14)
 6835.6 In reply to 6835.3 Hi Pilou, > And make rotate 60 then 15 of a cutting plane is not sufficient without move the cylinder? I don't think it is - the second rotation changes the "as viewed" (projected) angle of the plane's surface normal direction. Basically the Top and Front views are both connected to one another because they share the same right-left x-axis direction. So if you do any transformation in the top view that changes position in the x axis (including rotation), it will disturb the angle as viewed in the other view. When you want things to adhere to a particular 2D silhouette it's usually better to work more with the silhouettes and have those extruded... - Michael

 From: BurrMan 25 Jul 2014  (7 of 14)
 6835.7 In reply to 6835.5 Thanks again. 2 planes intersection it is.....

 From: Ditto 26 Jul 2014  (8 of 14)
 6835.8 In reply to 6835.2 >>> DAN : "... (still waiting on v3 to buy) ..." Definitely OT, but you may buy v2 now, get immediate access to the v3 beta and the free update to v3 once it comes out.

 From: Michael Gibson 26 Jul 2014  (9 of 14)
 6835.9 In reply to 6835.8 Yup that's correct, if you purchase v2 now you will get a free upgrade to v3 when the final version comes out which won't be too much longer. - Michael

 From: Dan (MONTAGMAN) 26 Jul 2014  (10 of 14)
 6835.10 In reply to 6835.9 Thanks for the heads-up. I might do that.

 From: Dan (MONTAGMAN) 27 Jul 2014  (11 of 14)