VraySun Reflection Causing High Render Times

This scene is not a piece of art, as I was trying to discover the best way to add lights to a building for night animation.

Settings are LWF Linear 1/1 2.2 gamma, Vray 1.5 RC2. It’s a simple scene with simple glass. Using Physical Camera ‘Video Camera’ so the exposure doesn’t go crazy while turning the scene.

But in doing these tests, I came across really high render times around frame 70:

26 minutes

Sub-pixel mapping OFF
Clamp Output OFF
Affect Background ON

47 seconds

Sub-pixel mapping ON
Clamp Output ON
Affect Background ON

1 min 46 seconds

Sub-pixel mapping ON
Clamp Output Off
Affect Background ON

The buckets on DR hang right at the reflection of the sun on the glass.
I was going to post this file in a different section, but for now you can test it by downloading it here.

Hm. Can’t help tho, but seems adaptive tracing doesn’t work… Strange, isn’t it? Or I’m mistaken, coz I don’t see any “adaptiveness” :smile:

Well - I’m amazed that the times vary from 47 seconds with all those checked versus nearly 2 hours without some of those.