Caustic problem!!

tpdesign

Hello. I am using SketchUp 2017 and Vray3.4.

I am now doing a caustic rendering test.

The problem of caustic sphere during testing occurred.

The first image is a caustic result by "spot light". - It is normal.

The second image is a caustic result by "Sun light".

The caustic of sphere is strange.
The result is the same even if IOR of the refraction is given various values.

So I tried to configure the same scene using "Vray sun" in 3ds max.
"Vray sun" is equivalent to "Sun light" in sketch-up.

Is this a bug in sketch-up vray3.4? Or am I misusing it?

I also uploaded this skp file.

I am looking for help. Thank you.

Spot light caustic

sun light caustic_problem

3ds max VRAYsun scene image