Render layers allow users to separate their scene geometry into parts, where one part is meant to be visible and the rest of the parts “capture” the side effects of the visible geometry on it. The layers allow different objects to be rendered into separate images where in turn some normal render passes may be applied. The Render layers are meant for compositing and not to hide parts of the scene itself.
This option works most efficiently in single frame render. Animation renders are a bit cumbersome and time-consuming with this option. Because it is not efficient to render only one layer ID and then go back and render other layer IDs. So you can use "Render Layer Mask" as an alternative to this option. It's running like Cinema 4D's native "Object Buffer" option and allows you to do the same function much faster. As for the shadows, you can use the diffuse material "Shadow Catcher" and for the reflections you can use only "reflection pass". Now let's explain the options.
Used to activate and deactivate this option.
Let's say you have a scene like the one you see in the picture below, and you want to extract some objects from this scene and render it. and again let's say that you will render the ground and Octane Logo separately. In such a case, assign "Octane Object Tag" to your objects in the scene. Then go to the "Object Layer" tab in the Tag settings and define the Layer ID for the objects you selected. set 2 for Octane Logo and set 3 for the Ground.
Info: Do not use Layer ID 1 due to technical reasons. Always start from 2.
Info: For the Render Layer to work, go to Kernel Settings and activate the Alpha channel.
Now go to the "Render Layer" section of the Render Passes settings, enable and enter the relevant numbers in the Layer ID section. If you do this you will see the result in Live Viewer. For example if you made 2, you'll only see the Octane logo, if you made 3, you will see the floor.
The main beauty pass will render only active layer and cut out everything else. But you can reverse this process by toggle the invert option.
This determines the visibility mode that should be used to render layers.
Normal: The beauty passes contain the active layer only and the render layer passes (shadows, reflections...) record the side-effects of the active render layer for those samples/pixels that are not obstructed by the active render layer. Beauty passes will be transparent for those pixels which are covered by objects on the inactive layers, even if the object on the active layer behind the foreground object.
Hide inactive layers: All geometry that is not on an active layer will be made invisible and no side effects will be recorded in the render layer passes, i.e. the render layer passes will be empty.
Only side effects: Similar to ‘Normal’, with the exception that the active layer will be made invisible to the camera, i.e. the beauty passes will be empty. The render layer passes (shadows, reflections...) still record the side effects of the active render layer. This is useful to capture all side effects without the active layer obstructing those.
The real power of the render layer feature is in the shadow and reflection layer passes, where the “side effects” of the render layer are captured. They allow users to compose the render layer on some background with shadows and reflections.
Octane Render distinguishes shadows as either of two shadow types: “black shadows” and “colored shadows”.
Black shadows are caused by opaque materials or specular materials that do not have the “fake shadow” option enabled. They are what the matte material is capturing and can be composed using normal alpha blending.
Captures colored shadows cast by objects on the active layer geometry. Only objects with a specular material with fake shadows enabled can cast colored shadows. This pass doesn’t have an alpha channel and should be composed in via the multiply blend mode.
Captures light reflected off of objects on the active layer on objects on the non-active layers. This pass respects the materials so the look of the reflections really depends on the materials used.