Black lines where a transparent mesh intersects I have a simple piece of geometry with a cloth simulation on it (a tube). I have a second piece of geometry rigged to it with a bone chain. I need the cloth simmed piece to not render, so I made it fully transparent. However, in areas where the two pieces intersect, I get black lines. How do I prevent this?

Normally I would use a mask modifier to hide the simmed geometry, but that causes the bone chain constrained to it to get messed up as the geometry it is constrained to no longer exists.

Disabling rendering of the cloth object entirely isn't an option as other parts of it need to render, and it's running off a mesh cache, so I can't alter the object.
Up the Max bounces under Render > Light Paths > Transparency to a high number, even numbers like 48 or higher. The more overlapping transparent surfaces there are the more likely to get black artifacts if the transparency bounces isn't high enough.
If that doesn't work, perhaps check the normals aren't getting inverted mid-way, but it's likely the former.

You could also disable the cloth rendering completely by unticking everything under the Object Panel > Cycles Settings, which should speed up the render.