© Disney/ Pixar

Bump Roughness was created for efficiently sampling micro details in Cars 3. With this pattern, RenderMan automatically switches from a bump map to a roughness value depending on the size of a feature in the camera, effectively improving  your render times by lowering the sampling rates needed to render such details.

One such example is Louise Nash (shaded by Yeon Kang) from Cars 3. Here you can see extensive wear of the clear coat on the paint job, which creates micro-scratches and breaks up the specular in interesting ways, also driving the anisotropy in ways which more accurately reflect the intended look-development.

A crucial feature of Bump Roughness is to keep micro details when objects are far from the camera, as shown in the example above.

There are many other types of materials that benefit from the added detail that Bump Roughness maps bring, such as carbon fibre, metals, plastics, and fabrics.

© Disney/ Pixar

PxrBumpRoughness

b2r Texture

This expects the first derivative map, let H be a height field, then each channel are defined as r=dH/du, g=dH/dv, b=dontcare

Texture Type

Map type to be used as your Bump Roughness Map

TxMake Icon

Show settings in Texture Manager

Manifold

Connect a manifold node here to control the position, rotation and tiling of your Bump Roughness map

Multi Manifold

Connect a PxrHexTileManifold or PxrRoundCube Manifold here.

Bump Roughness

Base Roughness

This is the roughness of the base surface when fully zoomed into the detail

Texture Roughness

Set the texture roughness to be provided by the input textures when fully zoomed out from the detail. It is combined with the base roughness. The default of -1.0 lets the texture provide its natural roughness.

Gain

This is a multiplier to the aggregate roughness

Bump Normal Gain

multiplier to the normal map magnitude

Anisotropy Gain

This is a multiplier to the aggregate anisotropy

Advanced

Adjust Amount

Amount to adjust the normals when they are facing away from the camera

Surface Mix

The amount to mix the resulting normals with the surface normals

Blur

Amount of blur to apply to texture lookup.

Filter

Which filter to use. (unfiltered/closest not advisable for displacement.)

Filter Scale

Multiplies the size of the texture filter, less than one for sharper textures.