Indentations problem in curved surface when tapering

Hello guys.

I just stumbled upon a difficulty that I have probably missed a thousand times before were it not for having my model rendered in Thea renderer.

Here is the real counterpart of the model I wished to create in SU.

So I went about it in the following way: I first created a Slice:

Then I copied this in a rotation so as to make the whole geometry of the outer ring on the lamp:

After cleaning the top and bottom out, grouping the whole object and after having disabled the viewing of the hidden lines I went about tapering the top with Fredoscale’s excellent tool and got this:

All very nice. Right?


Look closely at the surface of the lamp’s ring, with the default SU shading:

When it has been rendered it is even worse (quick render just with a golden material put on top of a pedestal):

So, the real question is:

  • Is there any other way to model this. Am I doing anything wrong?
  • Is this a SU problem?

Any help?

I would perhaps model this differently, by first creating a regular cylinder, then tapering it by scaling the top surface, and adding the slits afterwards. This would create less triangulation in the finished model. What happens with your model if you turn on Hidden lines?


Like Anssi suggested, turn on Hidden Geometry.

Create the elongated openings within the face of each segment, not across two segments.

I think you need more segments on the curve of each slice. I didn’t see any dimensions, but I used a 12" diameter base circle with 60 slots. Using one slot per slice as you did, I created each curved face with 5 segments and used 24 segments for the curves at the ends of the slots. The result was grouped as a component, rotated 6 degrees, and replicated 59 times. This was all created at 1000x scale and then scaled back to size when completed.

Using the default SketchUp smoothing, you can still see faint highlights, but they’re much less emphatic:

If this isn’t sufficiently smooth, you can just use more points on the initial curves.

I don’t have a decent way to render this, but I’ve attached the model in SketchUp 8 format in case you would like to render it as a test: lamp.skp (32.0 KB)

Hey Guys,

Thanks a ton for your suggestions.

I’ve tried your suggestion and it seems smooth enough. I uploaded a small video for you guys to see rendering in real time all across the model.
just click here.


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Hello jimhami42,

Just rendered your solution and it resulted in some artifacts, albeit different ones.

Here’s a pic:

Thanks anyway,

Are those edges soft and smooth in SketchUp?

Yes they were smooth in SU. But this smoothing is just for viewing it inside SU. Not in any other package.

Interestingly enough we have here in this example three different ways to do the same thing and they do yield different results too. My first effort was the worst, lol. But hey we’re always learning.

I wager that this is the kind of thing you will find in all 3D modeling apps, one way or other. Not this specific instance but generally speaking.

Thanks for all your help guys. I’ll post the final model when done!.

Clearly not what you were looking for :wink:

I appreciate you taking the time to render this for me!

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I downloaded a trial version of Thea and used it to render different models I have. I really like it a lot :smile:

I’ve decided that there is magic in SketchUp surfaces created with arcs. I used the following circle and semi-circle to generate four different spheres:

All four spheres were created with the Follow Me tool; the first used the native arcs; the second used an exploded path; the third used an exploded template; and the fourth used both an exploded path and exploded template:

This is further highlighted by creating semi-cylindrical prisms and using Thea to render them as optical lenses:

The five prisms on the left were created with the 3-point Arc tool; the five on the right by exploding the arcs before using the Push/Pull tool; the red one in the center used 100 points on the arc.

Magic, I tell you, it’s magic :wink:


It goes to show that you can definitely not make omlets without eggs! (sorry Portuguese saying).

Want some smooth light behavior? Then be gentle and be smooth. She (the renderer) will comply!

That was a vey nice analysis you’ve made there and I thank you for sharing that with us!

Now if only Thea went so far as to develop smart shaders into their material Lab! Hope this whole EU and Greeece stuff won’t hinder their efforts!