User manual

© Next Limit Technologies 2010
Maxwell Render 2.5 User Manual
Chapter 10. Maxwell Materials | 62
10.03.03 Specific properties
When selecting a material component in the layer tree (a BSDF, a Coating, an Emitter
or a Displacement component) its properties will appear in the right area of the Material
Editor. These components form the foundation of the Maxwell material system, and they
are explained in the following chapters.
10.04 The BSDF
The BSDF component is the main component in the Maxwell material system. It contains
all the parameters needed to create lots of different types of materials, ranging from
clear glass to sandblasted glass, plastics, metals and translucent materials such as skin,
porcelain, and wax. In this rst section we will go through each parameter in order,
providing brief descriptions. In the second section we will show different material examples
and discuss the settings used.
When a BSDF is selected in the material layer, the BSDF properties are displayed in
the panel on the right hand-side. The controls are divided into 3 distinct areas: BSDF
Properties, Subsurface Properties, and Surface Properties.
The BSDF properties handle all settings related to the material as a whole. The Subsurface
properties control the effect of translucency – or light that is scattered beneath the surface.
The Surface properties handle all settings related to the surface of the material, such as
the surface roughness and bump.
10.04.01 BSDF Properties
Reectance 0º / 90º
F.01 Texture slot
This is the light reected by the material. In other words: it is the color of the material.
Choose a reectance color by clicking on the Color Picker, or specify a texture by clicking
on the Texture slot (image above). You can enable or disable the texture using the check
button near the Texture slot.
A full white reectance (RGB 255) means that all the light that falls on the object is
reected back. Black reectance (RGB 0) means that all the light is absorbed. Please note
that the reectance colors describe the amount of light the object reects back, but not
how that light is reected back (in a diffuse way, or a specular way for shiny objects).
This is instead controlled by the Roughness parameter. See the Surface Properties chapter
which describes how smooth or bumpy the surface is.
There are two reectance colors: the light reected when the object is seen at 0º degrees
(frontal view) and at 90º degrees (glancing angle). The Reectance 0° is the object’s main
color. The Reectance 90° color (also called Fresnel color) is the object’s color at glancing
angles. This is useful when you have a material which reects one color when viewed
straight on, but at sharper viewing angles reects another color, such as taffeta, silk, and
velvet. Think of the Reectance 90° color as the object’s “specular” reection.
How much inuence the Reectance 0° color vs. the Reectance 90° color has on the
look of the material depends mostly on the roughness settings and to a certain degree on
the Nd. You can nd more information on these two parameters and how they affect the
inuence of the Reectance 0° vs. the Reectance 90° colors in the following chapters.
For most materials, the Reectance 90° color is white. However, materials like metals
usually have tinted reections. For example, if you would like to create a golden material,
you should set the 0° color to a yellowish tone and then use a brighter yellow for the
reection 90° color so that the specular reections become tinted as well. Changing the
Reectance 90° color allows for different reected colors at the edges of the object.
u Important: Avoid setting the Reectance 0° color too bright. Setting it to 255 for example
means this material will reect back almost all the light it receives, which does not happen
in the real world. Maxwell Render still keeps the amount of light reected/ absorbed within
physical limits but the result with such high Reectance values means the light will keep
bouncing around in your scene with very little loss in energy, which will produce noisier
renders and a washed-out look with very little contrast. A reasonable setting even for very
bright materials would be around 230-240. For example, the Reectance value of a white
piece of paper, when converted to RGB, is around 225. Please note that this only matters for
the Reectance 0° color. The Reectance 90° color can be left at fully white (RGB 255).
Transmittance
This parameter controls the color of the light when it passes through a transparent