It is possible to render curves with Arnold. An Arnold Curves tab is provided.
Currently, there is no checkbox to avoid SSS computations in point and curve primitives. However, the use of SSS is not supported with point and curve primitives and is therefore not recommended.
You can modify the orientation by using the name ar_orientations with an attribcreate node (Tab > Attribute > AttribCreate). The ar_orientations attribute is per point and is a vector representing the direction towards which the curve ribbon is facing at this point of the curve.
Attribcreate name set to 'ar_orientations'
The Default Radius property can be overridden with one of the following attributes to provide more control or randomization of the width.
To implement this, use an attribcreate node (Tab > Attribute > AttribCreate) to modify the attribute.
HtoA will check for these three attributes, in order:
Note that Arnold specifies a radius for curves but the traditional Houdini width and pscale attributes are diameters. When using width or pscale, HtoA will half the value entered to use as the radius.
The curve width is overridden using the ar_radius attribute with the value ($PT*$PT)/200