I am a complete CAD beginner. The recent Home Shop Machinist article on OnShape got me clicking and five minutes later I was starting to draw shapes on the computer. Nice.
I like how, on the plane, I can specify what I know about a shape and OnShape then fills in what more is needed. For example, you can drop down three points and then specify each of the three connecting lines is 1 inch and it will position the points as an equilateral triangle and tell you the angles are 60 degrees. (And, of course, much more complicated, including telling me when I have over-specified a system).
Now, I want the same capability in three-space. Drop down four points in three-space. Specify all six edges are 1 inch, and I want the computer program to jiggle them around as needed to give me a tetrahedron. BUT, I don't see how to do this.
I can place a unit-length equilateral triangle centered on the origin. Then, on the axis perpendicular to the triangle center, place a fourth point. Then define a plane with point 4 with points 1 and 2 so that I can draw a line from point 4 to point 1. Now, when I try to dimension that new line to 1, I get an error. What I want is for it to slide point four along the plane I defined it on so that the distance becomes 1.
Using other approaches I can make a tetrahedron using OnShape. Not a big deal. But it requires I do some math. I want OnShape to do in three-space what it does nicely in two-space.
What am I missing? And, if OnShape does not do three-space math, which of the score of CAD programs does?
Thanks for helping me get going here. If this has been discussed before, my apologies, I will happily take a pointer and read the threads.
Cordially,
Bill
I like how, on the plane, I can specify what I know about a shape and OnShape then fills in what more is needed. For example, you can drop down three points and then specify each of the three connecting lines is 1 inch and it will position the points as an equilateral triangle and tell you the angles are 60 degrees. (And, of course, much more complicated, including telling me when I have over-specified a system).
Now, I want the same capability in three-space. Drop down four points in three-space. Specify all six edges are 1 inch, and I want the computer program to jiggle them around as needed to give me a tetrahedron. BUT, I don't see how to do this.
I can place a unit-length equilateral triangle centered on the origin. Then, on the axis perpendicular to the triangle center, place a fourth point. Then define a plane with point 4 with points 1 and 2 so that I can draw a line from point 4 to point 1. Now, when I try to dimension that new line to 1, I get an error. What I want is for it to slide point four along the plane I defined it on so that the distance becomes 1.
Using other approaches I can make a tetrahedron using OnShape. Not a big deal. But it requires I do some math. I want OnShape to do in three-space what it does nicely in two-space.
What am I missing? And, if OnShape does not do three-space math, which of the score of CAD programs does?
Thanks for helping me get going here. If this has been discussed before, my apologies, I will happily take a pointer and read the threads.
Cordially,
Bill