The Maxwell Material shader operator stands for the layered material system used by Maxwell Render. Maxwell Render’s materials are made up of different “components” such as BSDF (Bidirectional Scattering Distribution Function) and Coating, Emitter or Displacement. These components are organized into layers which are stacked one on top of the other. This special hierarchy is represented by tabs and multilist controls on the interface of the Maxwell Material node.
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Material properties
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The main tab of the Maxwell Material node contains the following global properties. - Load MXM: load the material description from the specified .mxm file. The SHOP node is renamed to the name of the loaded material.
- Reload: updates the parameters from the .mxm file. This button is useful if the .mxm file has changed outside Houdini (for example edited with the Material Editor).
- Save MXM: exports the material to the given .mxm file.
- Show Preview: calls Mxed to calculate preview of the material by the current settings. The preview image is displayed in MPlay.
- Edit in Material Editor: opens the Material Editor (Mxed) with the current parameters which provides a user-friendly interface to edit the material. After the material is saved and the editor is closed, the plug-in reloads the material parameters automatically.
- Dispersion: enables / disables the dispersion calculations. Dispersion is the effect which can be seen when different wavelengths of light are refracted at slightly different angles as they pass through a material. The amount of dispersion can be controlled with the Abbe parameter of the BSDF component.
- Shadow: enables / disables the shadow catcher, used for compositing purposes.
- Matte: enables / disables matte properties for this material.
- Material ID Color: specifies color identifier for the material, useful for compositing.
- Global Bump Mapping: enables using global bump map which will affect the whole material, alongside the bump of each individual BSDF.
- Bump Strength: specifies the strength of the bumps.
- Bump Texture: specifies a bump texture where brighter values will create bumps on the surface and darker values will create indents. A color map can be used as a bump map but only the grayscale information of the map will be used.
- Use Bump Texture As Normal Map: if checked, the given bump texture will be used as a global normal map. A normal map has the advantage specifying an angle, or the direction of the bumps while bump map can simulate only the up / down direction.
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The coating component has the following parameters: - Enabled: enables / disables visibility of the component.
- Name: name of the Coating component.
- Thickness: specifies the thickness of the coating component. Can be specified by a numerical value or through a weight map. To avoid interference coloring, higher thickness values (such as 1 mm = 1000000 nm) should be used.
- Min / Max: specifies the minimum and maximum value of the thickness used with a thickness map only. The thickness map will be treated as a grayscale map using the given range.
- Use IOR: allows users to set the value of the index of refraction (Nd) manually.
- IOR File: specifies an .ior file which provides Maxwell Render with the exact index or refraction for each wavelength of a material. These materials have the advantage of being extremely realistic, but complex IOR data requires more complex mathematical functions.
- Reflectance (0°): specifies the light reflected by the material, when the object is seen at 0° degrees (frontal view).
- Reflectance (90°): specifies the light reflected by the material when the object is seen at 90° degrees (glancing angle).
- Nd: specifies the overall reflectivity of the object (IOR: index of refraction). With transparent materials the Nd also controls the amount of refraction.
- Force Fresnel: specifies behaviour of the reflectance between 0° and 90° (the Fresnel curve).
- K (extinction coefficient): specifies the amount of absorption loss when an electromagnetic wave propagates through a material. This coefficient plays role in the calculation of the refraction at a particular wavelength.
- Use R2: gives controls over the falloff between the 0° and the 90° color.
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Material palette
The easiest way to create a material is browsing the default Maxwell materials using the Material Palette window which can be found in the Windows menu. It has a group called Maxwell where the following materials can be added to the scene:
- Maxwell BDSF: a layer with a bsdf node.
- Maxwell Coating: a layer with a bsdf and a connected coating node.
- Maxwell Displacement: a layer with a displacement node.
- Maxwell Emitter: a layer with an emitter node.
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