Blender Cycles Freestyle Line Breaking

Question

I'm trying to make a short 5 minute toon shaded starship scene with Blender Cycles. The ship(s) in the scene also have a toon outline created by two line sets, one thinner one set to only render on creases and edge marks and one thicker one set to only render on object contours. It looks good and like the way I want it to be, but when I render an animation (camera flyby) I notice that on some frames certain lines break. You can see that here: https://youtu.be/czazInaUevc

That looks pretty ugly. Is there any way this can be avoided or at least greatly minimized? Here's the scene's .blend file: https://drive.google.com/file/d/1ceVqcvQTiVrjOe-18zJdUkYJpaEqc1QP/view?usp=sharing

Answer 1

You have to adjust your model (topology) to be better compatible with freestyle.

Two problem of your geometry are

• intersections
• very sharp angles

^{left: intersections; right:sharp angles}

Freestyle isn't designed to work with intersections. An intersection will remove other lines if freestyle wrongly thinks that a line segment is occluded (even though it may be only partially occluded).

If you are using Smooth Shading and Subsurf Modifiers, you should consider checking Face Smoothness. The manual is quite vague

When enabled, Smooth Shading will be taken into account for edges calculation.

However, I have found that some edges with wouldn't be connected, are connected with Face Smoothness enabled.