Mari 4.6v4 docs:

Unreal

Note: Results may not be as expected if you do not use the Environment Light in the Lights palette when using this shader.

Control	Type	What it does	Dialog	Notes
	toggle	Toggles the influence of channels connected to the shader without disconnecting them from the shader input.		Displacement is toggled off by default.
Inputs \| Base Color	dropdown	The channel controlling the overall diffuse color of the material.
Inputs \| Roughness	dropdown	The channel controlling how rough the material is. Rough materials scatter reflected light in more directions than smooth materials.
Inputs \| Metallic	dropdown	The channel specifying the areas on the material that have a metallic effect, with results being determined by values between 0 and 1.
Inputs \| Specular	dropdown	The channel specifying the non-metallic areas on the material where the specularity is visible.
Inputs \| Ambient Occlusion	dropdown	The channel used to specify the self-shadowing that occurs on an occluded object.
Inputs \| Normal	dropdown	The channel containing the Normal map, used to give additional physical details to a surface.
Inputs \| Bump	dropdown	The channel containing the bump map to show as a perturbed lighting.
	button	Inverts the channel values of the selected channel.
Inputs \| Emissive Color	dropdown	The channel controlling the color of the emissive (glow) qualities on the shaded surface.
Inputs \| Vector	dropdown	The channel controlling the vector field and resulting vector data from paint on the shaded surface.		This data is used by the vector inspector.
Inputs \| Displacement	dropdown	The channel containing the displacement map and dynamic tessellation to show a more advanced preview of displacement.		This component is disabled for Ptex channels.
	button	Adds a new channel for the shader component.	Add Channel Dialog
Displacement \| Displacement Bias	text field, slider	How much the white or black values are pushed or pulled from the surface.		From 0.000 to 1.000; defaults to 0.500.
Displacement \| Displacement Scale	text field, slider	How much displacement is applied to the shaded surface. Lower values equal smaller displacement; higher values equal larger and more obvious displacement.		From 0.000 to 1.000; defaults to 0.500.
Displacement \| Displacement Range	text field	What the range of displacement is. This setting is multiplied by the Displacement Scale to give the displacement.
Displacement \| Max Tessellation	text field, slider	How many texels the surface is tessellated to.		From 1.000 to 64.000; defaults to 10.000.
Displacement \| Perturb Normals	dropdown	Selecting yes changes the displacement so that displacement moves the surface but leaves the surface normals as they are.
Bump \| Bump Weight	text field, slider	How much weight the bump map has. Lower values are smaller bumps, higher values are larger and more obvious displacements.		From 0.000 to 10.000; defaults to 0.100.
Bump\| Bump Mode	dropdown	Displays bump quickly (Fast), accurately (Accurate), or less accurately (Fastest).		By default, Bump Mode is set to Fast. While Fastest is very fast, it works better with live procedural layers rather than painted or cached layers.
*Bump* \|Bump Space	dropdown	UV - Normals are calculated relative to the UV coordinates space. The UV Bump Space mode is the more traditional approach but can lead to noticeable seams and color variations. World - Normals are calculated relative to the World coordinates space. Using the World Bump Space mode gives a more seamless result.		By default, Bump Space is set to UV.