This appears to be the same issue as posted in this thread a few weeks ago.

My setup: SolidWorks Premium 2013 x64 SP5.0, no maintenance contract.

When rendering an assembly with contours only, extra contours that you wouldn't normally see in the view seem to get rendered.

This is what it looks like as PV360 is starting the render:

And this is how the finished render appears:

I can only assume that it's some of the detail hidden inside one of the subassemblies - maybe a bearing housing etc.

Is there any sort of fix for this?

The assembly of the machine you can see in the second image, obscured by the duct, is actually a SLDPRT file containing hundreds of bodies (created from an assembly), so hiding the bodies inside the part at the location of the "ink spot" isn't simply a case of right-click > hide subassembly.

UPDATE:

None of the following steps have fixed the problem:

• Replacing the SLDPRT file of the machine behind the duct with the original SLDASM file
  
• Hiding internal components the newly-inserted assembly of the machine behind the duct
• Making the duct solid instead of hollow (though this does seem to have reduced the density of the artefacts - see below)

Thanks,

Chris