Cinema 4D / BodyPaint 3D Program Documentation Tutorials Camera and Render Settings Tutorial
Function available in CINEMA 4D Prime, Visualize, Broadcast, Studio & BodyPaint 3D

Using Multi-Passes

The second method of including the depth of field effect in your image(s) is to use Multi-Passes. With Multi-Passes, various image components and properties such as shadows, specular highlights or Global Illumination - or even masks and depth of field effects - can be rendered (and saved) as separate bitmaps.

When using Multi-Passes the Depth of Field effect should remain disabled in the Render Settings menu and, for example, only RGBA - which is equivalent to rendering with an integrated - and Depth of Field should be enabled in the Render Settings’ Multi-Pass menu. This list also includes all available Multi-Pass options. As you can see in the image below, Multi-Pass can be enabled or disabled separately and assigned its own image Format and File. If you have enabled the RGBA Image option you can ignore the Regular Image options entirely.

The example below shows how a Multi-Pass render could look for our red-and-white room. At the left is the RGB image and at the right is the grayscale information for the depth of field effect. This can then be placed over the RGB image in Photoshop via its blur filter. This method gives you more flexibility when experimenting with various blur effects without having to re-render the image in Cinema 4D each time. This is especially helpful when rendering animations since animated Depth of Field effects can be used effectively here as well.

Multi-Pass renders are perfect for subsequent image editing (incl. image sequences, i.e., animations). However, you should always make sure that the passes will combine to create a complete image - at least with regard to coloration. Otherwise the image cannot be "reconstructed" when the passes are overlain. The Blend Channel Pass is a good basis for later reconstruction of the image(s) (see image below). Here you can enable all image components for which you do not want to render a separate pass.

These channels must then each be rendered in separate passes. The original image can then be reconstructed by successively overlaying each of these passes. You will then have access to each individual pass in Photoshop where you can, for example, modify brightness, specular lighting or other components. The image below shows possible components of a Multi-Pass image. At the top is the Blend Channel Pass channel, as it was set up in the previous image. At the center and bottom are the Global Illumination and Reflection passes, respectively.

When saving in BodyPaint 3D or Photoshop file formats the passes will automatically be arranged correctly and the layer modes will be set automatically as to create the final image. Since we did not mention Ambient Occlusion as an additional multi-pass component, we have added the following image that shows the subtle difference (right) when it’s applied:

The entire RGBA image is used as a reference in the background. If you want to access the sky in front of the window, which is part of the Ambient in the blended channels, the RGBA image must be generated and the alpha channel must be enabled in the render settings.

The Save option must not be enabled. As shown in the image below, the normal complete image will be output as an additional pass, including a mask for the entire room. What remains are the slits for the windows, which can be used to cut out the sky from the rest of the image.

Generating Alpha Channels Using Multi-Pass

Creating a mask using the Alpha Channel option only works if the scene’s background is not blocked by geometry. If you want to create a mask for a specific object in a scene you will have to use the Compositing tag to create individual masks for objects or groups in the Object Manager. In our example we will select the table in front of the sofa. The Compositing tag offers numerous options, e.g., to enable or disable the object’s visibility in reflections or even for the camera itself. Switch to the Object Buffer tab. Here you can enable Buffers with which an object can be assigned masks when rendering with Multi-Pass.

To do so, add the Object Buffer Pass option from the Render Setting’s Multi-Pass menu and enter the number assigned in the Compositing tag’s Object Buffer tab. The image below shows the Object Buffer Pass setting and the resulting mask for our scene.

Numerous Object Buffer channels can be rendered separately using Multi-Passes. Simply add Object Buffer Pass options accordingly and enter the Object Buffer ID you want that particular Object Buffer Pass to render.