Render layers in Blender

Render layers in Blender can be a bit confusing to new people as their behavior is not related to other applications such as photoshop . Render layers are used a lot in compositing and can be used in conjunction with other techniques to reduce the computational time in rendering a complex final image.

The key to the understanding the render layer lies in two menus those being the layers menu and the render layer see below.

One quick tip to duplicate the objects between layers that the are identical in both layer is to duplicate the objects (shift + D) and then copy these elements (M) to the relevant layers.

Now that the objects are in place different passes can be defined so that they can be composited at the end of the render. The example given below show the effect of reducing the harness of the background shadow. To accomplished this effect in one render a series of spot light would have to be set up to achieve the effect of a gradual effect in the changing come of the shadow the downside is the increase in computation time of the render.

Now the setup

Layer 1 Light with plane Layer 2 Cube on its own

Note it is important to select the Do composite and make sure that nodes have also set. The node structure can be seen with the end result.