Post Production in Octane for C4D
Part 1: Setup and the AOV System
Part 1: Setup and the AOV System
About this guide
No matter how good you get at producing renders straight out of the engine, at some point you’ll probably want to do some work in post production (or hand off work to someone else to do so). This is a pretty broad topic with a lot of information, so we’re going to cover it across a series of guides.
This first part focuses on the setup and the mechanics of the AOV system. Part 2 is a deep dive that explains what each AOV/pass does. This series also contains a setup checklist to help you remember all the various steps to creating a multipass project.
Note: This guide uses the terms AOV and Render Pass interchangeably.
Note about versions
This guide is written for the 2021 release of Octane. The entire render pass system has been revamped, and the AOV system has been fully implemented in this version. The information about the passes themselves is still valid for older versions of Octane, but anything having to do with AOVs is really only relevant to the 2021 release and newer.
Setup
Before you even get started with passes, there are other things that need to be considered so that what you render can be properly used in your post-processing application.
Multi pass Settings
Pretty much all of the settings needed for multi pass rendering will be found in Cinema 4D’s Render settings (the clapboard icon) - not Octane’s settings (the gear in the live viewer). You’ll need to choose Octane Renderer as your Renderer in the dropdown, and then once that’s selected, there are things to change in the Main, AOV groups, and Render AOV group tabs.
The most important setting when doing multi-pass rendering is Enable checkbox. If this isn’t checked, your passes will not be saved, and you’ll be sad.
Saving Files
Traditionally with Cinema 4D’s built-in engines (Standard/Physical), you’d use the Save and Multi-Pass sections of C4D’s Render Settings on the left to save your renders.
If you’re rendering multiple passes with Octane, you’ll want to use the Render Pass file field Render AOV group tab to put in your path and filename to save your files and set all the options.
You can still use C4D’s Save section to create a reference PNG render that has post effects applied. If this is enabled, it will render at the same time as the multi pass version. Most of the time you’ll probably want this off so you’re not cluttering up your drive with unnecessary files.
File formats
As a general rule, when rendering for motion graphics, it’s always better to render out a still image sequence rather than a movie file, and then bring the sequence into a post production application to composite and create a movie file from it. If the render stops for any reason, all the still frames rendered so far will be intact, whereas a movie might be corrupted and a full restart of the render would be required. For this reason we’ll be covering still image formats going forward.
Octane itself natively supports PNG and EXR formats. C4D can also output other formats like PSD, TIFF, TGA and JPG, but those can produce unexpected (and very much undesired) results. In this guide we are going to concentrate on EXR since it’s the best format for Multi pass AOVs.
OpenEXR (usually just known as EXR) is far more versatile than PNG for compositing. Multiple passes can be stored in a single EXR file, and it allows bit depths of up to 32-bit for when very precise masking or heavy post processing is needed further down the pipeline. It also supports multiple color workflows including Linear which we will be using in these guides.
Octane for C4D has two different EXR format options. The Octane-native EXR(Octane) format is typically what you’ll want, especially if you’re using a Cryptomatte pass. The other EXR format should only used if you have legacy files which use Render Layer Masks.
EXR Compression Options
The EXR file format has several options for compression. Usually Piz compression gives you the best bang for your buck as far as file size and quality goes. If you end up with quality issues in post software, you can try using RLE which compresses it less and produces larger files. If disk space is more of an issue than precision, you can also try some of the lossy compression algorithms like DWAA.
Multi-layer vs multiple image sets
If you’re outputting to EXR, you have the option to store all your passes in layers in the same EXR file, or create individual EXR files for each pass. Both ways have their pros and cons.
The single layered file method has a little less up-front work when setting up your file structure, and produces fewer files to manage. Multiple EXR sets gives you the flexibility to re-render just a single pass and easily replace it in your comp. Also, if you find you’re not using a pass, you can just delete the folder to save space, where you can’t easily modify every file in an multi-layer EXR animation to remove a pass.
There’s no wrong answer here, it’s just personal preference if you’re working alone, or if you’re working on a team, choose the one that fits in with the pipeline you’re using.
Linear Workflow
This is a topic that’s been covered in great length in other guides and videos on the Internet, but it’s worth mentioning here that if you aren’t using ACES or another specific color workflow, it’s recommended that you use Linear when rendering multiple passes for post production. You get far more flexibility and better colors with Linear (or ACES) than sRGB.
Camera Settings
In Octane’s settings (the gear icon in the live viewer, not C4D’s render settings), in the Camera Imager tab, check the Natural (or Neutral) Response checkbox. If you are using the Octane Camera tag and have the Enable Camera Imager checkbox on (which overrides the global Camera Imager settings), be sure to click the Neutral Response checkbox there as well.
Render Settings
In C4D’s Render settings, in the Octane Renderer Section, in the Main tab - change the color space from sRGB to Linear sRGB. If you’re using an ACES workflow, you can choose the appropriate setting there instead.
The AOV System
As mentioned before, the original Render Passes system has been replaced by the newer AOV system in the 2021 release.
There are two different ways to use this new system to generate passes. If you just want to generate a set of standard passes (diffuse, specular, emission, lights, post, etc) to recompile in your post production application, all of that can be easily accomplished in the Render AOV group tab.
The AOV groups tab is for more complicated setups where you want to do some (or all) of the actual compositing within Octane. This method is best managed in the node editor because of the complexity of all the pieces.
These two systems are not compatible with each other. If you add a bunch of passes in the Render AOV group tab, you can’t then go into the AOV groups tab, pop open the node editor and start stringing them together into more complex setups. You’ll need to re-add all your passes from scratch. Think about how intricate you need your system before choosing one system over the other.
Render AOV Group Tab
This tab contains everything you need to generate a set of simple passes to be recompiled in a different app.
At the very top, there’s an Enable checkbox. Remember to check that (yes, it's been mentioned before, but it's really important).
Right below that is all of the saving/format options that we discussed earlier in this guide.
Below that there are five buttons. Add render AOV and Render AOV manager allow you to add AOVs to your project. Remove render AOV will remove the last AOV you added. Node editor will open the node editor if you prefer to work in nodes, and Convert Render Passes to AOVs is for updating legacy files produced in Octane 2020 and earlier.
At the bottom, there’s a twirldown section for Render layer (more on this in the AOV Deep Dive Guide), and once a pass is added, there will be another twirldown section for Render AOVs where you can disable/enable them, rename them or change the type.
Add render AOV
This button will add an AOV, or a render pass to your file. When you click it, a list will pop up of all the available passes divided up into buckets.
This method is super quick and easy for a few passes (let’s say you just wanted a beauty pass and a post effects pass), but it can get tedious if you have more than that. For anything more complex, you’ll want to use the Render AOV Manager.
Render AOV Manager
The Render AOV Manager button will pop up an interface that quickly lets you add a lot of passes in bulk. Once the window is up, just start double-clicking the names of the passes you want to add, and as you do that, the list in the render settings will update to match. If you click any of the added AOVs in the manager window, you’ll have the option to enable/disable/rename them. There are controls at the top that let you filter and search for specific AOVs. You can delete or reorder the AOVs here as well.
AOV Groups Tab
The AOV Groups tab is for when you want to get really serious with AOVs. Here, you can set up complex groupings of AOVs so you can audition different looks, and actually do some/all of your compositing from within Octane itself without having to go out to a post processing app.
Note: You still need to use the Render AOV Group tab to set the file path and format settings, and enable AOVs with the checkbox at the top.
This tab uses Cinema 4D’s system of nested twirldown sections and the add/remove input/layer buttons, but it can get really tedious and confusing. If you’re going to go all in with compositing, it’s really best to do it via the node editor.
Remember, anything done here is not compatible with any of the passes you create in the Render AOV group tab.
The Way of the Node
The node editor can be called up in several locations. In the Render AOV Group tab, there’s a node editor button in that set of 5 buttons in the middle of the screen. In the AOV Groups tab, the button is in the AOV groups section. In the Render AOV Manager window, there’s an icon with four connected boxes to the right of the Available AOVs dropdown that will also launch the node editor.
The Octane Renderer Node
Every scene has exactly one Octane Renderer node. This is the node representation of the Octane Renderer settings. If you click it, on the right hand side of the node editor, you’ll see all the same settings that you would if you went to C4D Render Settings>Octane Renderer. It’s literally the same information - anything you change here will also change in the Octane Renderer settings window.
This node has two types of inputs.
The Render AOV input is for individual Render AOV nodes only. The individual Render AOVs are the ones managed in the Render AOV group tab of the render settings. You add more inputs by hitting the Add Render AOV button on this tab. You can only delete the last input you added, so you’ll have to do some rewiring if you want to remove empty ports (empties don’t affect anything, they just make the node larger). All said, there’s no real advantage to working with regular Render AOV nodes in the node editor - these are better managed in the Render AOV manager as described above - so we’re just going to focus on composite AOVs going forward.
The Composite AOV input is for composite AOV nodes only. These composites are managed in the AOV groups tab of the render settings, but there’s also a set of nodes at the bottom of the list on the left that you can drag out to create composites. You add Composite AOV inputs by clicking the Octane Renderer node, and in the AOV groups tab, hit the Add input button. Similar to the render AOV tab, you can only delete the last input you created.
Composite AOV Nodes
There are several nodes you can use to build up complex networks of composite AOVs.
Render AOV Output node
This has similar functionality to the Render AOV node - it’s a basic building block that contains a single, unaltered render pass, and not much else.
This node can connect directly into the Composite AOV input in the Octane Renderer node, but at that point you may as well just use the Render AOV system. The real power of the composite AOV system is the compositing.
Composite AOV Output Group and Composite AOV Layer nodes
These operate in a similar fashion as the Material Layer system. The Composite AOV Output Group node is a container for multiple Composite AOV Layer nodes.
One Render AOV Output node (or an AOV output group node) gets fed into one Composite AOV Layer node. This node gives you the ability to change the blend mode, add a mask, and add a basic color tint for anything fed into it.
All of the Composite AOV Layer nodes are fed into a Composite AOV Output Group node which combines them all into a single output that goes into one of the Octane Renderer’s Composite AOV inputs.
This is a little confusing at first, but it starts to make sense as you use it. The whole system is broken up in a modular way so that you can combine all these nodes in a ton of different ways.
AOV Clamp, AOV Map Range & AOV Color Correction Nodes
These nodes are similar to some of the material mapping nodes. They can sit anywhere in the chain - you can use them to alter a single AOV pass, or a layer, or a whole Composite AOV node depending on what you need.
Image AOV output, & Color AOV output
These are similar to Image Texture and RGB Spectrum nodes - they can be combined with passes to use as masks or color correction constants.
Rendering Composite AOVs
Once you are done setting up your tree, as long as Render Passes are enabled in the Render AOV Group tab (and the save settings and everything are set up properly), Octane will render all of your Composite AOVs (Out1, Out2, etc), and also each individual Render AOV Output (single unaltered pass) that you have in your node network. From here, you can finish up your work in post.
Check out Part 2: AOV / Render Pass Deep Dive to learn more about the passes themselves, and there's also a checklist to help you remember all the various settings for each project.
