The Null Material node is used for mesh objects that have an invisible surface but contain a medium. This is equivalent to setting up a specular material with IOR 1 and a reflection of 0 and a transmission of 1. However, that methodology no longer makes sense with nested dielectrics. The Null Material was created to make a medium with no surface work in all cases.


Null Material

Figure 1: The Null Material parameters.

 

Null Material Parameters

Medium - Accepts any medium node.

Opacity - Controls the transparency of the material via a greyscale texture.

Affect Alpha - If enabled, refractions will affect the alpha channel.

Displacement - Adjusts the height of a surface's vertices at render time using a texture map. Displacement maps differ from Bump or Normal maps in that the geometry is altered by the texture, as opposed to just creating the appearance of detail. Displacement mapping is more complex than using a Bump or Normal map, but the results are more realistic, especially along a surface's silhouette. Displacement works with the texture nodes, and the displaced mesh must have UV Texture coordinates. Procedural texture nodes, such as Turbulence or Marble, need to be converted using the Baking Texture node. For more information, see the Displacement topic in this manual.

Smooth - If disabled, normal interpolation will be disabled and triangle meshes will appear facetted.

Smooth Shadow Terminator - If enabled, self-intersecting shadows are smoothed according to the polygon's curvature.

Round Edges - Rounds the geometry edges by using a shading effect, rather than creating additional geometry. See the Round Edges topic in this manual for more information.

Priority - Used to resolve the ambiguity in overlapping surfaces, the surface priority control allows artists to control the order of preference for surfaces. A higher number suggests a higher priority for the surface material, which means it is preferred over a lower priority surface material if a ray enters a higher priority surface and then intersects a lower priority surface while inside the higher priority surface medium

Emission - This creates a medium that emits light. To activate an emission, connect the Emission input to either a Blackbody or a Texture emission map. The Textures and the Mesh Emitters (under Lighting Overview) topics in this manual cover maps in more detail.