Aug 15, 2012

Multipass Compositing with Cinema4D and After Effects 02

In the previous part we learnt how multipass works, now we'll take a look at how to save the passes and take them to After Effects.
Saving multipass composites is just like saving standard renders. Open up render settings and under "Save", you'll find a new section: Multipass:

I'm sure you know how to use the "File" section. It's best to give passes their own folder. Especially with image sequences, things can get messy. So in your project folder, you can just create a folder "passes".

Next, we have FORMAT. This part is very important.
For one, you want to have 32-bit files in order to store as much information as possible. But aside from that, there's a few factors to consider.
Selecting a format like Photoshop (PSD) will enable the option "Multi-Layer File". This means that ALL the passes are saved as layers in one file per frame. Unlike using JPEG where you'll end up with one image per pass per frame. To elaborate, you'll find you have Frame01_AmbientOcclusion.jpg, Frame01_Diffuse.jpg and so on. FOR EVERY FRAME.
This tends to get messy. So I find multi-layer files are more useful. So, I tend to render out PSD. There's also the option of using multi-layered TIFFs and OpenEXR (R13 and up), but there's a better reason to use PSD over those two formats.

Another thing you may want to ask is whether or not you want to save the beauty pass, which is the fully composited image. Depending on how confident I am about the result, I usually switch it off. But it's a good idea to keep it close in case of anything.

Prepare to Render

So we'll check the settings. Multipass is set to separate lights with 3 channels. Since I have this, I don't need to have Diffuse, Specular or Shadows under multipass, since all the lights are being separated.
Then, I'll add extras. Motion Vectors for motion blur with RSMB, Material UVs for remapping textures (if I need to) and finally Depth for the camera (you may need to set up the camera settings yourself).

We can render a single frame just to see how things look. I'm going to render frame 90 with saving on.
I'll head over to my save directory and check the pass file in Photoshop:

One file holding 12 layers of multipass. A good 68.6 MB though

In Photoshop, you can see that Cinema has taken the time to order the layers and name them accordingly.
For comparison's sake, here's how it would look if we rendered single-layer OpenEXR at 32bit:

Interestingly, they're only 1.95 MB. The first disadvantage with this is that the filenames are MESSY. You can't tell which is which. However, they're taking MUCH less space on the hard-drive. In fact, JPEGs only took around 250KB! So how can we work with the smaller 1.95MB without having to worry about how to importing all those images?

Compositing File

It took me a while to realize that there's one other feature in Cinema that I almost completely overlooked: Compositing Files.

Compositing files are like generated templates of your render. I explain more in the next chapter.
In the "Save" section, at the very bottom you'll find "Compositing File". Check the 'Save' box. A compositing file will be created when we render.

So now that we have the saving settings set, I'm going to go to AE and import the file:

Cinema has automatically placed everything in folders, and created a comp with everything organised properly. You may also notice that all lights are separated as their own comps:

Cool! That's extremely handy!

That's it for this post. In the next one, we'll look at how to fix the strangely bright viewport and how LUT works.

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