Artifacts appear based on distance from the viewing point

I have a fence panel with a separate cap in each picket tube top. The cap has dog ears that fit down inside the picket tube and should be entirely hidden from an external perspective. If you zoom in tight, everything looks proper.

When I pull back, the artifact appear as a little circle:

Looking down the pickets, the further you go from the viewpoint, the larger the artifacts show up.

Any suggestions as to what might be causing this?

Best regards,

Hello - can you post a file with one of these pickets?


Good evening Pascal,

Here is the picket subassembly and cap 3dm files. (attached)

Appreciate you giving this a look!!!

Thank you!


875x1dot5FLATcapSOLID.3dm (562 KB)

PicketSubassy.3dm (9.02 MB)

Hi Bruce - - the caps are interfering with the posts - that is, they are inside the walls of the posts

So the depth sorting is not working out too well.
if that is how it should be for some reason, I’d put those extensions on their own layer and turn the layer off for rendering.

Incidentally, I don’t know how specific that design is but you can greatly simplify the caps


if you are allowed to deviate very slightly from what you have.:


andf even if you are not:



Good catch. Actually, there’s an error on the tab model, as it’s a friction fit. I need to recheck the mfgr spec, I’ve likely picked up a lesdexic number. That will take care of the depth sorting.

Your smooth and straightforward surfaces for the top of the cap were what I was attempting to achieve, but I evidently was missing the use of the proper tool to get there.

Can you offer guidance of how you constructed this? I am likely missing something simple.

Thank you!

Hi Bruce - in this case, starting with what you have, one way is

  1. ExtractSrf and delete complicated flat sides.
  2. ExtractSrf the two narrower tapered sides that get rounded off at the top.
  3. BlendSrf between the top edges of these. Adjust the sliders (lock them together) in BlendSrf to match the roundiness of the top that you want,
  4. Join the blend surface to the two sides and then to the base of your cap - that will make a thing with two large gaps where the complicated planes were.
  5. Cap the result to add those planes

But, starting from scratch , you could make 2d curves from eacg view, extrude them to fully intersect each other, and then trim them to one another


Your suggestions worked great!
Thank you for your good help!!!