I have a fully dynamic dress draped over a screen. In my first picture, the dress appears to be passing through itself where it is colliding with the top edge of the screen.

I selected cloth self-collision and it did this, so I did a second simulation in which the dress also collides with itself, but it still does it. Can anyone tell me what I'm doing wrong, please?

The next post illustrates my second problem.

I just thought of something as I was typing. Would I do better to drape the dress over a high res square instead of the screen it's going to be on in my scene?

(edit) - I think I mean a suitably scaled box, not a square.

you are right in your idea, cloth collisions only work well on the correct side of the polygon. dont ask me why, I dont know.

your best bet is to add a primitive cube and shape it to be the same (relatively) as your screen.

when setting collision settings on the cube modify the collision offset appropriately to stop your object poking through, the offset is the amount of space between the colliding object and the cloth, the higher the number, the less chance it will poke through. the downside is that if too high, you get a visible, and unrealistic gap between your cloth and its collision object(s)

its entirely likely that you could fix your problems solely by changing the offset, however I would suggest using the cube anyway, as you can shape it to better give you the results you want

You may want to check the other collision detections as well, it will help detect collisions where large polygons exist. Collision depth and offset may be tweaked . using a non-visible collision plane (cube etc) can also make things easier.

Thank you both! Using a cube fixed the second problem, plus playing with the collision offset and depth. The dress is still showing those horrible marks along the top fold, though, which I assume are self poke-through (they are not AO, as I switched that off). I'll play a bit more with those dials...

tick "normals forward" on all material zones on your prop to see if that helps the shading. the dark areas in your renders are the backfaces of polygons.

it wont fix anything, but it will help hide it