Chapter 4: mental ray and materials Multi/Sub-Object materials are one of the common methods of assigning more than one material to a single object, but it is dependent on having faces or polygons in the correct configuration. Sometimes the geometry layout has nothing to do with the material assignments, so you will learn another method of applying multiple materials to single objects using "masking." 4.5.2 Maskingtechniques The concept of masking in 3ds Max materials makes use of the luminance values, or brightness, of pixels in a map or image. White pixels allow the underlying effect to show, black pixels block the effect, and gray pixels partially block the effect. For example, if you mask a reflection map with a black-to-white gradient ramp, you get for reflection in the white areas, no reflection in the black areas, and diminishing reflections based on the brightness of the gray areas. You'll learn to use masking to satisfy the client's wishes to have two separate materials on a wall, a white paint material and a checker pattern material. The configuration of the faces in the wall geometry make it impractical to use the Multi/Sub-Object material and Material IDs. Like many clients, this one hasn't completely made up his mind on exactly what configuration he wants the materials to be, so it's important that you work as flexibly as possible to be able to adapt to future changes. The solution in this case will be a Blend material that has a built-in mask slot. Much like the Multi/Sub-Object material, Blend is a standard material type that can contain two Arch & Design materials as sub materials with