Strange things when bevel object to a curve

Using Blender 2.79. When I use a curve as a bevel object along another curve, sometimes my bevel object suddenly flattens to a weird plane-like thing. I can see what looks like a mesh that has weird faces/normals, but since it’s a curve, that’s not possible. It sort of follows the shape of the curve, but it’s unpredictable. It doesn’t happen all the time. And, I’ve done this many, many times before with out any problems. Is there a bug? Even the simplest trial (as a test) I open a new file, add a bezier curve (I do NOT scale, rotate or change location) and add a bezier circle as the bevel object. Again, I do NOT scale, etc. Then I select the curve and select the circle as the bevel object, and I may or may not get the curved tube that one would expect. Sometimes it just looks like a flat, weird plane.

show some pics for problems
and sample file if possible

happy bl

Yeah some pictures would definitely help to see exactly what’s happening :slight_smile:

I explained exactly what happens. I could create a file I suppose, but as I described, it happens even with the simplest file after startup. Just a curve and a circle as the bevel object.

sorry but have used this very often and never had any problems
so you will have to be very specific on the problems !

happy bl

Well I don’t know how much more specific I could be. As I said a simple bezier curve with a bezier circle as the bevel object, without doing any scaling, rotating or transforming at all, right from a fresh, new Blender startup file, and the problem is there. I would expect the circle to become a tube that is curved along the bezier curve. But instead, I get a flattened thing, that does follow the shape of the bezier curve, but looks like a flat mesh that has weird normals. Of course it’s not a mesh at all.

upload file so we can see the set up
then we can help more

happy bl

I’m going to take a guess that something is happening with scaling along one of the axes. (Expanding the N-panel would show it. A “flat” curve can still be scaled along an axis.) If scaling isn’t 1,1,1 (as seen on the N-panel) then CTRL-A followed by S should make the scaling uniform. If that’s the case, your circular bevel object should spring forth into the expected shape.

Paul thanks. But if I NEVER changed anything after adding a curve, wouldn’t the scaling automatically start out as 1,1,1? That’s why I’m puzzled because I start a brand new Blender session, delete the cube, add a bezier curve and a bezier circle as the bevel object and that’s all. And instead of a tube along the curve, I see a flat “thing” along the curve instead. As if the circle was flattened to a plane.

Did you just bevel ‘BezierCircle’ with ‘BezierCurve’ as bevel object? If so, do the other way around.

No, bezier curve with bezier circle as the bevel object in the curve panel. No taper object.

Could you attach some screenshots showing the problem as people trying to help you kindly asked?

I tried to recreate the problem, but for some reason now it is working OK. If it happens again I will post the screenshots.

That’s the thing. I fail to create a problem when trying as well. :smiley:

Just for the record, if anyone else also finds this thread using Google…

The trick is that the shape you want to extrude along the curve must be in the local XY plane of the bevel object. In fact, before extrusion takes place, the contents of the bevel object are projected to the XY plane of the bevel object. It is the same as if you had switched the Shape of the bevel object to 2D.

If your extruded shape is on the local XZ or YZ plane of the bevel object, then it will be reduced to a line when projected to the XY plane, and this line will be extruded along the curve, resulting in a flat extrusion.

I added the above to the Blender 2.90 documentation.

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