Read Materials From Attribute – This option is enabled by default. It finds the materials directly from the @shop_materialpath attribute in the geometry, if the material(s) are present in the Material SOP. If the material is placed in the Render tab of the geometry node, this option should be disabled. 

Select Material – If Read Materials From Attribute is disabled, this option becomes active. It looks for a material in the Render tab of the geometry node. You can choose an arbitrary material here.

Viewport UV Set – Specifies the name of the UV attribute used by Houdini to show the material in the viewport. You can leave this name as is. 

Set Viewport UVs – The ViewportTex SOP "translates" to Houdini all UV transformations made in V-Ray's texture and material nodes. This way, UV manipulations can be updated and displayed in the viewport.

Auto – Uses the Viewport UV set name to set the material attribute.
From ImageFile – Sets the name of the UV material attribute the same as the UV texture attribute. However, UV changes are not shown in the viewport. 
Manual – Allows manual setting of the viewport UV attribute for all materials. It is recommended to switch first to From ImageFile, then to Manual, as the default option is Auto - which means V-Ray automatically assigns UV attribute name. 

UVs Attribute Type – Specifies where the UV attribute is saved: 

Vertices
Points

Show Warnings – This option is enabled by default. It displays warnings if there are any UV attribute name conflicts. If there are missing attributes, the objects will be colored in orange and if part of an animation, will start blinking. If there is an attribute set name that coincides with the Viewport UV Set, the object(s) will be colored in red and if part of an animation, will start blinking.