I've imported an STL file from a CAD program the the object in Blender is to be a smooth glass item. Unfortunately, when I render, it comes out very jagged.

After importing, I implemented an Edge Split and Smooth shading. Despite these additions, the object looks like what is attached. Considering that it's basically a modified disk, it should be smooth through the object. Any suggestions on how to rectify this issue? Thank you!

Jagged Glass item

  • $\begingroup$ Can you upload a .blend file? $\endgroup$ – Shady Puck May 24 '16 at 16:36
  • $\begingroup$ I'm afraid I can not. It's for my work. $\endgroup$ – Cod-nerd May 24 '16 at 16:56
  • $\begingroup$ If you have the option use .obj, .fbx or .3ds for transfering data. That doesn't quarantee good results but you will want quads always. the jagged surface is probably originally an n-gon, you could select the jagged area and start cutting appropriate lines fromedge vertex to another with K. $\endgroup$ – kheetor May 24 '16 at 17:05

The STL from a cad program is not going to have good topology. Topology is important for smooth shading and even more so for a glass shader.

It is kind of hard to tell from that one picture, but your mesh may have more issues then just bad topology.

A quick and easy way to possibly fix your mesh is to add a Remesh modifier.
Remesh modifier settings

That modifier will make a completely new mesh (out of evenly sized quads) that closely matches the shape of the original.

  • $\begingroup$ Thank you! I've had this issue many times and the remesh was the best option so far. It doesn't work so well for really complex shapes but it certainly handles most very well. $\endgroup$ – Cod-nerd Aug 17 '16 at 18:04

You can try to repair you mesh with some tools. As i don't know your topology, let's use a simple cylinder with NGons as an example. all views Here you have the views of the cylinder with a subsurf, smooth shaded and the rendered view.
1 : the supposed original mesh, with NGons
2 : the same mesh triangulated, as your imported mesh is supposed to be.

Now let's quadify it. Select all with A and then Alt+J. This might be enough to fix your mesh if there was no NGon in the original one.
3 : quadified mesh
If there was some NGons, select the face loop around the cylinder (possible with quads) with Ctrl+Alt+Right Click.
select face loop
Invert the selection with Ctrl+I
invert selection
Use F to make the faces NGons. NGons are supposed to be flat.
Now we're at step 4, or back to 1 : the original mesh.
Select your NGons, use I to inset, move your mouse to place your edges and left click. Do it again if necessary.
5 : repaired mesh

  • $\begingroup$ Thank you for this answer! You gave a very nice and detailed response and I appreciate that! $\endgroup$ – Cod-nerd Aug 17 '16 at 18:05

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