Multilayered materials
Maxwell Render’s stacked layers system allows you to create complex and very sophisticated materials. Each layer corresponds to a specific material, so each layer can contain several BSDFs blended together, coatings, SSS, etc. Think of a layer as a complete material on its own, with its own displacement, BSDFs, and coatings.
To create a partially rusty metal sheet, begin by creating the rust layer. Apply a Refl 0º map and a bumpmap. Roughness should be a high value (for example 100). Name this layer “rust”.
Now create a new layer over the first. Name it “paint”. You can use the Wizard to quickly apply a car paint material. Or combine two or three BSDFs to copy the look of a clean, newly-painted metal sheet. Adjust the weight value of the “paint” layer to mix it with the “rust” layer underneath, or better, use a grayscale map as a mask to remove the “paint” layer from certain areas, allowing for the rust to peep through.
You can also load a global bump/ normal map that will be applied to the whole material from the Material Properties row in the Layers list. Each layer can have one displacement component but only one of the displacement components will be used for rendering. You can specify which one you wish to use for rendering in the Material Properties panel.
For more details on using Stacked Layers, see the Stacking Layers page in the Maxwell Documentation.
Find more multilayered examples at the MXM Gallery.