
This setting omits or blocks volumes from rendering when they pass into the interior of the glass object. This turns off reflection but allows rendering pure refraction/transmission. This ignores the setting in the integrator to collect alpha values based on glass opacity/refraction. The below interior parameters are not meant to operate in this mode. If on, correctly split energy according to Refractive Index between reflection and refraction, but do not bend the ray in refraction (simulating a double pane of glass with a single pane or maybe a hollow glass ornament). This allows the user to artistically override the refraction index set in the glass lobe for calculating caustic light paths in conjunction with the controls for Manifold Walk found in the PxrUnified integrator. This sets the glass object to allow exploration for caustic light paths, used with PxrUnified integrator and the options for the Manifold Walk Use Thin if you want to avoid bending rays. Higher Ior values bend rays more than low values. Online resources of Ior values can provide more useful settings. The default is 1.5 which is typical of glass. Below the reflection is non-rough (0.0) while the refraction roughness increases slowly. When set to a non-negative number, allows the refraction roughness to be different than the reflection, which is controlled by the Roughness parameter above. Here is where you would simulate frosted or etched glass. This allows you to create objects that are realistically colored and have colored shadows just like real transmissive objects (note that Thin Shadows should be enabled on your lights). A setting of 0.0 results in an unrealistic look as seen in the first image below. Low numbers decrease the visible reflection result.

Lower numbers result in less light making it through the object and might appear as dark tinted glass or simply black at 0.0.

Turn the gain for Diffuse to 0.0 for pure glass.

Also note that when creating glass for the first time, you will find the default gain of 1.0 for Diffuse may interfere with your look. Using one or the other alone may result in interesting effects but isn't intended by design. The Refraction and Reflection Gain controls are meant to work together.
