How To: Generate a Mist Pass
Cycles 4D can generate a mist or fog effect using the cyEnvironment object. If you want to do this, here is how.
Turn on the Mist Pass
First, turn on the mist pass in the Render Elements tab of the render settings. If this switch is unchecked, no mist pass will be generated.
Turn on multipass rendering
The mist pass is a post effect, so in the Cinema 4D render settings turn on Multi-Pass and add Post Effects (and the RGBA image and any other passes you want, of course).
Set the Mist options
In the cyEnvironment object, you can set how far from the camera you want the mist to start. This is the Start setting. Then you can set the distance until the maximum mist effect is reached - the Depth setting. The longer this distance, the lesser the mist effect will be on objects closer to the camera (basically, a thinner mist is the effective result).
Even at the maximum Depth the effect can be quite strong but you can reduce it in the Layers tab of the picture viewer or use a compositor such as Photoshop to tone down the effect if required.
Render the image
When you render the image you will see a Mist layer in the Layers tab of the picture viewer. As usual when you save the image make sure you save it with layers or you will only see one layer in the final output, making it impossible to alter the layers in Photoshop or another editor. By default in the picture viewer the blend type will be set to 'Add', when imported into Photoshop it will be 'Linear Dodge (Add)'.