CALCAD Posted March 31, 2011 Share Posted March 31, 2011 If I'm drawing in isometric style and I draw a line at some arbitrary angle, how do I draw a right angle? That is, a line that would be 90 degrees to the first drawn line if the 3D image were tilted into the display plane. Quote Link to comment Share on other sites More sharing options...
rkent Posted March 31, 2011 Share Posted March 31, 2011 You would have to first have an orthographic view of, say, the top view with the lines drawn there. Then you would either transfer the dimensions along iso lines and connect the dots, or do an actual iso projection to locate them. Or simply draw in 3D and use one of the iso views. Quote Link to comment Share on other sites More sharing options...
designerstuart Posted March 31, 2011 Share Posted March 31, 2011 or if you draw in planometric (aka oblique axonometric) instead of isometric, it's a lot easier. but i guess that's not what you want. Quote Link to comment Share on other sites More sharing options...
CALCAD Posted March 31, 2011 Author Share Posted March 31, 2011 rkent, Yes, taking dimensions from an orthographic view works, but I wondered if there were a more direct way. Maybe a trig formula. Wishful thinking perhaps. Thanks. designerstuart, I'm curious. Could you show or describe the planometric approach? Thanks. Quote Link to comment Share on other sites More sharing options...
designerstuart Posted March 31, 2011 Share Posted March 31, 2011 rkent, ...I wondered if there were a more direct way. Maybe a trig formula wow if your trig is quicker than a few offset lines, you are good! Could you show or describe the planometric approach? Thanks. to draw planometric you start with an elevation drawn orthographically, i.e. your standard parallel view. in most cases this would be your plan. this elevation remains undistorted by the 3d drawing process, unlike isometric. then you rotate it by whatever angle you want, usually 30 or 45º, and draw the vertical lines off it, to the same scale as the principal elevation. so then anything drawn in the principle elevation would be drawn exactly as it appears on a standard ortho view, as is scaleable, with all angles shown correctly. heights are also correct, but the other elevations are necessarily distorted. wiki doesn't seem to do it much justice but fwiw - http://en.wikipedia.org/wiki/Axonometric_projection http://en.wikipedia.org/wiki/Oblique_projection Quote Link to comment Share on other sites More sharing options...
designerstuart Posted March 31, 2011 Share Posted March 31, 2011 picture tells a thousand words...... Quote Link to comment Share on other sites More sharing options...
CALCAD Posted March 31, 2011 Author Share Posted March 31, 2011 designerstuart, I've done a few projections as you described, but never knew what they were called. Thanks for the explanation. About the trig or other mathematical formula, it presumably could be written in autolisp as a general solution, making it fast and convenient, if such a formula exists. Quote Link to comment Share on other sites More sharing options...
designerstuart Posted March 31, 2011 Share Posted March 31, 2011 it presumably could be written in autolisp phew! good luck with that! (but i am always blown away by what leemac and the lispers can do - if the numbers exist, of course it is possible somehow) Quote Link to comment Share on other sites More sharing options...
nestly Posted March 31, 2011 Share Posted March 31, 2011 I may be missing something, but either Isoplanes with Ortho/Polar tracking, or Isoviews with Ortho/Polar tracking seem as though they do what you're looking to accomplish without any math or lisps. They'll also be both visually and dimensionally correct. http://www.we-r-here.com/cad_08/tutorials/level_3/videos/3-2_isometric.html Quote Link to comment Share on other sites More sharing options...
CALCAD Posted March 31, 2011 Author Share Posted March 31, 2011 nestly, I rarely use polar tracking and it didn't occur to me to combine that with isometric style. Unfortunately I don't have Autocad to test the idea. I use Bricscad, Intellicad and Draftsight. As far as I can tell, none of these are capable of properly using polar tracking with isometric style. When I try to align the crosshair with an off-axis line (using either UCS or SNAP), the crosshair does rotate, but does not align with anything in particular and the polar tracking seems to default to standard orientation. I'm curious to know if this really does work in Autocad. Meanwhile, I'm still interested in a mathematical approach. Thanks. Quote Link to comment Share on other sites More sharing options...
rkent Posted March 31, 2011 Share Posted March 31, 2011 If you already have the orthographic top view simply use a program to create the iso view. This one is from cadalyst.com I believe. ISOVIEWS.lsp Quote Link to comment Share on other sites More sharing options...
Jack_O'neill Posted March 31, 2011 Share Posted March 31, 2011 Y'all are doing it the hard way. Draw your first line, then off out there somewhere to the side of it, draw another using the perpendicular osnap. Then move the second line to the end of the first one. Quote Link to comment Share on other sites More sharing options...
nestly Posted March 31, 2011 Share Posted March 31, 2011 Huh ??? ??? Quote Link to comment Share on other sites More sharing options...
CALCAD Posted March 31, 2011 Author Share Posted March 31, 2011 rkent, The program code looks intriguing, but seems to be missing several support files. When I have some time, I'll search them out. Jack_O'neill, The question is not simply drawing a perpendicular, but drawing it in isometric style. The rules are different in that mode. Thanks. Quote Link to comment Share on other sites More sharing options...
Quagga Posted March 31, 2011 Share Posted March 31, 2011 If I'm drawing in isometric style and I draw a line at some arbitrary angle, how do I draw a right angle? That is, a line that would be 90 degrees to the first drawn line if the 3D image were tilted into the display plane. [ATTACH]26782[/ATTACH] If your drawing is in iso, why would you draw at an arbitrary angle? even in bricscad you can switch ortho on and then change iso toggle to get lines at right angles. Al Quote Link to comment Share on other sites More sharing options...
rkent Posted March 31, 2011 Share Posted March 31, 2011 It should make its own DCL file, make sure the lisp file is in the search path for autocad. Options, Files, support file search path - to see paths that are defined and to add another. Quote Link to comment Share on other sites More sharing options...
Quagga Posted March 31, 2011 Share Posted March 31, 2011 It should make its own DCL file, make sure the lisp file is in the search path for autocad. Options, Files, support file search path - to see paths that are defined and to add another. The O.P. is not using AutoCAD, so I wonder why we are all answering his question. Quote Link to comment Share on other sites More sharing options...
SEANT Posted April 1, 2011 Share Posted April 1, 2011 The question is interesting. Here is a start on a trig method. IsoTop.zip Quote Link to comment Share on other sites More sharing options...
SLW210 Posted April 1, 2011 Share Posted April 1, 2011 The O.P. is not using AutoCAD, so I wonder why we are all answering his question. Last time I looked at the name of this site it was CADTutor. Mathematics would be the same anywhere and many AutoCAD solutions will work. If you do not wish to provide help, that is your choice. Quote Link to comment Share on other sites More sharing options...
CALCAD Posted April 1, 2011 Author Share Posted April 1, 2011 rkent, Looks like I just need to get the path right, as you suggest. SEANT, I'll have to study that awhile. Thanks. Thanks to all for your interest. I must now get some real work done before I can play. Quote Link to comment Share on other sites More sharing options...
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