3d-3 point arc
3d-3 point arc
(OP)
Using ACAD14 I am unsuccessful at drawing a 3-point arc in three dimensions. I've since found another procedure to get the arc almost the way that I want it but if I could specify 3 points in 3-space and have the program generate the required arc then it would be more accurate and a lot less trouble. I guess a better way to describe the problem would be to say that drawing sections of helixes is extremely difficult and I don't know what I am doing wrong.
Grapes of Wrath
Grapes of Wrath
RE: 3d-3 point arc
RE: 3d-3 point arc
RE: 3d-3 point arc
2) Draw a 3D line from the start point to the end point of your arc. Use object ucs and pick the line. Change the view using plan, currrent ucs. Draw your 3 point arc.
RE: 3d-3 point arc
The second message regarding a helix however, describes the situation that often drives one to make a 3d curve. A helix can be modelled using AutoCAD. The trick is in creating a group of nodes to use with a 3d polyline. Once a 3d poly line is used to "connect the dots", the solid>extrude>path command can be used to make a solid helix, like a spring. Making this a "true" curve may not be possible, I do not think AutoCAD will extrude along a spline path. It will extrude along a 3d polyline however. (the distinction to make here is that this method creates a "helix like" object, one that consists of a group of straight line segments, not a true curved object.)
Creating a group of nodes in 3d space can be done using a spreadsheet. Simply make a spreadsheet that calculates the x,y,z coordinates for each node. Import the coordinates using a script file. Once imported, create a 3d polyline that passes through each node. Draw a circle perpendicular to the node at one end. Extrude along a path and select the 3d polyline for the path. A helical solid will be created.
RE: 3d-3 point arc
Before you extrude along the 3D polyline path you can 'fit' the poly line (curve, cubical, or quadratic fit). Doing this will make the polyline look more like a spline (experiment with the type of fit and number of points used in the polyline to get the results you want - eg: you could draw a 'circle' with the polyline command using say 20 segments, but you may get as good or better results using 6 segments and then using a curve fit). One word of caution - 'fitting' the polyline essentially adds more points to it, which in turn adds to the time needed for AutoCAD to do calculations with it.
RE: 3d-3 point arc