Render > selected object with alpha in front of refractive object disregards alpha

V-Ray V-Ray for 3ds Max Issues
1

Tricky title, but this object is in front of a glass balustrade and as you can see, the alpha is not calculated.
Not sure if this is intended or a known issue.

Not really looking for mask-based workaround suggestions, just raising the issue…

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2

Is the balustrade shader’s refraction affecting all channels? Maybe attach the scene (simplified) so we can take a look.

3

Im finding it really hard to pin down consistently to be honest. I had thought this morning it was only an IPR thing, but the render I attached above proves this untrue.

4

Best send the scene so we can take a look.

5

Here’s a scene.

Very confusing. If I ensure affect all channels set for both reflection and refraction of the glass, it’s fine, but if this is no the case for reflection, weirdness ensues.
Also the non-black alpha parts seem to render additively each time I re-render (frame not clearing between each render). This is probably ‘normal’ but it’s the reflections that are disregarding the alpha? I’m not sure…

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6

Yes, you should keep both refl/refr as “Affect all channels”.

You can change this behavior through the “Previous render” option (Settings>System>Previous Render). “Clear” will clear the frame between renders.