Dish problem

I’m trying to generate a dish-like surface but am getting some strange results - I’d be grateful for any suggestions to resolve.

I have drawn 3 nested profiles in the same plane which are scaled versions of each other. To create the dish I have selected the two outer shapes & the annular surface in between & moved these perpendicular to the plane.
The resulting modified surface between the inner & middle profiles is not a neat minimum area surface - I have attached a file to illustrate:

  • In orientation A the faces parallel to the green axis are mis-shapen
  • If the task is repeated with the profiles rotated by 90 degrees (B) the problem recurs with the (now different) faces parallel to the green axis
  • C has been rotated by 45 degrees & suffers from some different defects though these still seem to be connected with alignment to the green axis

Am I making a simple error or am I using the wrong method to construct this shape?
(I noted that in performing the Move command inferencing did not allow me to pick up any features / points in the direction of the blue axis - I had to use an arrow key to constrain the move.)Dish problem.skp (2.9 MB)

With Curviloft plugin

with Split Tools and Move tool


That’s great Mihai - thanks. I’ll use this.
By the way is there a reason why I got such strange results with the approach I took?

Look at the second animated Gif.

// edit
If you show the program how vertices should be connected to each other, then the surface created is the desired one

Thanks - I’ll try this as well.

Thanks again - this is most helpful in understanding the root problem

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You should also be able to create the dish shape with the native Follow Me tool. Create a path that matches the shape of the base of the dish. Then create a profile that’s a cross-section of the side of the dish. Select the path. Click Follow Me in the profile. In my illustration, I filled in a missing face, then softened the resulting edge.

Hi David - Thanks for this. I did think about using Follow Me but it would have produced a different result. As the the tray outlines are scaled versions rather than offsets the profile needs to vary according to its position on the path.

Why do the outlines need to be scaled versions? Do you want the wall thickness of the tray to vary?

Using scaled versions is an aesthetic choice (the design isn’t a cooking tray).
I want the piece to have a constant wall thickness - my intention was to define the complete surface (there are a couple more features to add) & then construct an offset, perhaps using Joint Push / Pull. Do you think this is a sound approach?

Give Joint Push/Pull a try.What’s the worst that can happen?

I’ll have a go.
If you were modelling a complex shape to be made from sheet is there a recommended approach? I’m keen to get into good habits.

I’m not the best person to ask, as I use SketchUp for wooworking. Good luck with the complex shaping.

How would the real thing by formed? What kind of sheet? How would you be using the model you create in SketchUp?

I’m designing the housing for a clock which I’d use a 3D printer to make (from the SketchUp model) - given the complex shapes I want to use I don’t think fabrication from actual sheet is the most practical way for me to execute this.
Having said that, the nature of the design is such that however it is made much of it is composed of sheet-like structures, hence my previous comments.
What modelling approach would you suggest? Am I working along the right lines by starting with a surface & then creating an offset?

The offset method might work but seems like a potentially more complex way to go about it. If it gets you the results you want, though, you should do it.

I’m in the process of picking up SketchUp so I’m starting from a low base.
If there’s a simpler way of approaching this particular modelling task any suggestions / pointers would be gratefully received.

I think @davidheim1’s suggestion of Follow Me makes the most sense for what I see in your model. I didn’t understand what you found to make you reject that option.

For the piece I uploaded I wanted to use scaled outlines to define its shape. Because it is an oval the cross section of the wall is not constant around the perimeter & this is why I chose not to use the Follow Me function.
There are some more features I’d like to add to this part, also based on scaled copies of the same basic shape & for the same reason as above I don’t think Follow Me would produce exactly the geometry I’m trying to construct.
I hope this helps to clarify.

I guess I’m having trouble understanding why the cross-section is not constant. Is there some reason the wall thickness will vary?