Maxon Cinema 4D Forum
Partially hiding geometry in C4D
Partially hiding geometry in C4D
by Nick Hill on May 25, 2019 at 2:30:06 pm

I've got an object that's basically a series of thin discs. At a certain point in the animation a couple of discs raise up to reveal a load of geometry underneath them, so I've used a couple of boolean objects to reveal that as they go up, otherwise they'd stick out below the lower discs.

Trouble is, this makes rendering *really* slow: whether using the basic renderer or Octane it's taking about 2 minutes per frame. I don't need to create new geometry, so is there a way to hide it similar to using a track matte?

Re: Partially hiding geometry in C4D
by Brian Jones on May 26, 2019 at 7:16:46 pm

can you post the file?

Re: Partially hiding geometry in C4D
by Nick Hill on May 28, 2019 at 2:32:44 pm

I can't really as it's under an NDA. But I've done a bit more poking about to try and trap what was slowing it down.

It turns out it *wasn't* the two boolean objects, nor was it the Xpresso. It was one line of MoText wrapped to a circle spline.

With the MoText: 1m43 per frame
Swapping the MoText for a standard text object, lofted (but keeping everything else on - lighting, shadows, Xpresso, booleans, best AA): 8s per frame!

Is this a thing? Should MoText slow it down *that* much?

Compositing tags and include/exclude
by Nick Hill on Jun 11, 2019 at 4:56:23 pm

The project's moved on a bit, and I've ditched the booleans (as they seemed to slow things down a lot). I'm now hiding things mainly with transparent objects, then using compositing tags on the stuff that needs to be hidden with "seen by transparency" unticked.

However.... there are some objects that pass *behind* one of these transparent primitives. These need to be occluded by their *own* transparent objects, but *not* by any others. Here's a quick mockup example...

Currently, the blue cube's compositing tag has "seen by transparency" unticked. This means that both the transparent objects in front of it matte it out:

I want to stop the foreground transparent cylinder from matting out the blue cube. I'd have thought that the way to do this would be to drag this into the "exclude" box on the cube's compositing tag, but that doesn't seem to do anything.

Nor does dragging the blue cube's transparent box into the compositing tag on "include":

Anyone know how to do this? Or is there a better way? (I'd rather avoid multi-pass renders as that might become a bit of a headache for a project like this!)

Re: Compositing tags and include/exclude
by Nick Hill on Jun 12, 2019 at 12:33:03 pm

FWIW, someone helped me figure this out:

Re: Compositing tags and include/exclude
by Brian Jones on Jun 12, 2019 at 12:35:39 pm

thanks for the follow up