Thin walled glass not reflecting HDRI

[ValeroStudio]

Maybe I am missing something but I cannot get a thin-walled glass to reflect an HDRI. If I turn off the HDRI and just render the VRay sky, it's fine. The only way I could get it to work was to place it in the Background slot.

[ValeroStudio]

Upon further investigation, I noticed that an HDRI is not being reflected in the reflection pass but does appear in the specular pass. Has this always been this way? I feel like I have seen the HDRI in the reflection pass in the past.

[Peter.Chaushev]

Hello, Matthew,
Apologies for the late reply. I hope the following explanation will help you understand the results you described:

Since V-Ray Next Update 1.1 some of the render elements are rendered differently than before. The Lighting render element now contains all direct diffuse illumination and the GI element contains all indirect diffuse illumination. Similarly, all direct reflections of lights now go to the Specular element and all indirect reflections go to the Reflection element.

Previously this depended on the sampling of the lights and not just on the type of the contribution. Some of the direct contributions that should be in the Lighting and Specular elements were written to the GI and Reflection elements instead. In both cases they compose back to Beauty correctly but the different types of contributions are now split between the elements more consistently.

This change makes the elements more consistent but it's also needed for preventing artifacts in these elements with the adaptive dome light (and possibly in the future with other adaptive lights).
The raw elements are affected only when the corresponding normal and filter elements are available, otherwise they're rendered as before. This is because the raw elements have to be derived internally from the corresponding normal elements in order to work with the consistent elements.

The consistent elements are automatically enabled when the scene contains an adaptive dome light so they don't have artifacts. They are also enabled by default for both new and old scenes and can only be disabled via script access. For V-Ray GPU they are always enabled without an option to disable them.

Kind regards,
Peter

[ValeroStudio]

This is great information. Thank you Peter.