Draping Transmission Cables

[darylharr]

I have previously developed a work flow using AutoDesk Map to connect electrical poles or transmission towers with sagging cables for 3D modelling in landscape modelling software. I would like to use Vectorworks to handle this now.

I imported Georeferenced 3d points where I was placing electrical poles. Using an AutoCAD AutoLSP script and a DWG file of an Arc, I digitized lines between points. The script works out the scale factor between points and inserts a scaled draped cable. I can then export the 3D vector lines of the draped cables back into my landscape modelling software (VNS).

Any thoughts on if this can be done in Vectorworks. Any directions on how or resources to get me on the right track?

Thanks,

Daryl

[Benson Shaw]

One approach:

Connect the support points of a cable between two towers with a NURBS curve - two vertices. In the OIP click the Add Vertex button. This adds a third vertex, midway between the start & end. Set the OIP Move field to Vertex Only and numerically adjust the z value of the middle vertex. Or use the reshape tool in Z mode to drag the middle vertex. Refine the NURBS curve shape around the middle vertex by adjusting the value in the OIP Weight field.

This is a simple sag and does not correspond to any specific fall based on cable materials & tension, relative tower heights, complex curvature at the support points, etc.

If renders are final output, use the NURBS curve as Path for an Extrude Along Path. Profile can be any shape approximating the cross section of a cable - add a color fill. Triangle will have low CPU overhead (shortest render time), Circle will have high overhead. Maybe compromise on a hexagon? Only a closeup view will reveal the faceted cable.

You could also draw each cable as a continuous 3d Polygon drawn from support to support, convert that to NURBS. Use the OIP arrows to click from point to point and add a middle vertex in each segment. Adjust the z value as above.

-B

[Bryan G.]

Benson,

Great Pointer in the triangle and hexagon, so true but not always on your mind when designing.

[darylharr]

Thanks Benson, I'll give it a try. Much appreciated.