Creating a dome

[harlen.shaw]

I have BobCAD V24. I'm trying to create a half egg shell shape, basically an elongated irregular sphere. By drawing an outline of it first then create it from the 2d line. If anyone can walk me through how to do something this, it would be greatly appreciated.

Thanks

[BurrMan]

Hey Harlen,
Here is a quick revolve command video. I threw in a spline tool at the end to illustrate drawing a spline to maintain tangency at the end points.



What you see is I created 2 pick points that would be planar with the opposite (tangent) side. So if the "second pick" of the spline creation is a tangent point, you will maintain curvature for the revolve.

[harlen.shaw]

Thanks burrman, that helped alot. How would i go about it with this shape?

[BurrMan]

Hi Harlen,
Well, that shape starts to turn away from the norm and more towards an "organic" shape. Here are 3 methods.





You could use revolve still, if you can difine an axis for the shape, though, if it needs to adhere to "Both side" (The upper and lower part of the yaxis of the revolve) then you can loose that accuracy.

You can use sweep, and create a curve that sweeps around the path, to get a dome shape, but to get a continuously curved dome probably wouldnt work with that, because you would be trying to difine a "center" for the sweep of that shape, which would vary as the sweep rotates around and create some poor geometry in the top center area. So here, if it can stop short, you would have just a planar cap in the middle to fill (Note the pick points created will maintain tangency in those directions to allow a planar fill.

The best bet for doing a more organic shape is to have and use BobArt, which is designed more for this.. you can quickly make a dome and control its shape and look with a few parameters..

If you needed to make actual geometry to work with, or didnt have BobArt and the revolve and sweep didnt produce the type of result/curvature you needed, then the only other thing would be to start modeling the dome with some of the drawing tools and then surface them with some of the skinning tools.

[harlen.shaw]

Guess its time to start using my BobArt.

Thanks Burrman, you're the best. I feel like I owe you money for all the help.