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* February 15, 2020, 04:44:23 PM
When I extrude a torus along a line, it shows properly in the front,side views but in the top view, and main  it is flat.  Is there a way to correct this?
« Last Edit: February 15, 2020, 06:17:11 PM by TXFISH »


* February 15, 2020, 06:10:38 PM
As you can see in the attached screenshot, when I extrude a tous along a line, the front,back, are fine, fine, but the top and main views look like a flat line. How can I correct this? 
« Last Edit: February 15, 2020, 06:22:03 PM by TXFISH »


February 15, 2020, 09:27:13 PM

A torus is a 3D solid.  Extruding it along a curve is possible in DesignCAD but it makes no sense. I suppose it should be a 4D object, but those cannot be represented in 3D space. You will get innumerable internal sections that will totally screw up any other operations you try to do with the resulting 4Dx3D solid.

Perhaps what you want to do is extrude a plane with a hole in the center (cross section of a torus??


Now sit back, take a deep breath, and I'll try to explain some of the peculiarities of extruding along a curve (peculiarities is being especially generous - some might call them horrors).

1. The extrusion takes place relative to the object's position relative to the curve.

If the object's center and handle are located at the end of the curve there is a good chance the extrusion will follow the curve faithfully.

If the object to be extruded is positioned some distance from the extrusion curve the resulting extrusion  may do very strange things! But it can be made to work with patience.

The extruded plane should be perpendicular to the end of the curve. The location of the objects handles is very important in this respect. Best results are found if the object has a single handle.

If the object is positioned at an angle to the end of the curve you will get a flattened extrusion. If the object is oriented along the direction of the curve (as appears to be the case in the example you posted) you will get a bizarre and useless ribbon with bazillions of internal facets.

2. Whether or not you get a true solid depends upon what you extrude. Extruding a circle (circular line)  will produce a hollow "pipe" with zero thickness walls - not a solid.  Extruding a circular plane with a hole in it (torus cross section) will produce a hollow pipe with non-zero thickness walls - a true solid. Extruding a filled circle (plane) will produce a solid "rod."

3. The behavior of the extrusion - the way it progresses - depends upon the curvature of the extrusion curve.

If the curve lies in a 2D plane (curves in one direction only) the extrusion will not rotate - the top of the extruded object remains "up" relative to the plane of the curve.

But if the extrusion curve bends in two dimensions (does not lie in a plane) the extrusion will rotate around the extrusion curve unpredictable. This is especially noticeable if the extruded object is something like a square or rectangular plane. The extrusion will spiral around the curve. You cannot use "Extrude along a curve" to make banisters or railings on helical stairways.

4. Take a deep breath! Objects like planes, lines and curves are made up of points, and there is a point order for everything. This point order affects the way the extrusion progresses.

Sometimes the extrusion actually occurs backwards! It starts at the opposite end of the curve from where you snap to the curve. For simple extrusions like rods this may not be noticeable. But if you are brave and try a variable scale extrusion the results mat be backwards. In this case, select the curve, open the Info Box and click on the button with the red/blue arrows. This reverses the point order. Then try the extrusion again.

Sometimes the point order of the plane that is being extruded causes the extrusion to do weird things. Select the object and reverse the point order as described above. Then repeat the extrusion and see if it comes out right.

If neither of these point order reversals works, try reversing the point order of both the curve and the object.

5. If none of these things works shut down the computer and go get a beer!

Actually, there are some extrusion tutorials on the forum and quite a bit of discussion. It take practice and a lot of luck to get "Extrude along a curve" to work the way you want it to.


DesignCAD user since 1987