Having color problem in rendering using Vray

[Anonymous]

Hello everyone, I am making a video in which a glass ball falls on the floor and breaks into thousands of pieces. In this project, I have used Rayfire to break the ball in pieces and then applied vray material to all. The problem is, when the ball is about to hit the ground it changes it color to somewhat black. This happens at frame no. 335 or maybe 336 and it lasts for a few frame and after the ball totally breaks the color becomes normal as it is supposed to be.

I am providing the URL to my project file folder in which 3Ds Max project folder, a image (which I used as a viewport and an environment map), A HDRI Map (which i used to have GI Reflection/Refraction) and a video telling how this scene supposed to be.

Please look into this project and help me to get rid of this problem.

URL -  https://drive.google.com/open?id=0Bx55vNDvOW3yak9PSzM3eGV4bjA

Thank you.

[RobH2]

It looks to me like just as it's about to hit the ground it's refracting its own shadow back up through the glass. If you disable the balls ability to cast a shadow and rerender those few frames does the black stop? If so, a minor tweak on the refraction parameters might just fix it. 

[RobH2]

After a quick look it appears as if the fragments inside the sphere are interacting with the solid sphere just before it hits the ground. If you select and turn off all the fragments at about frame 338, the darkness goes away. 

I'd start diagnosing the fragments. Select them all and begin to adjust their properties. Clone your glass material and assign the new material to your fragments only and start tweaking that material. Having a separate material on only your fragments will give you a lot more control. 

You might also try having the fragments be invisible until just when the ball hits the ground. However, I do see a lot of black in the fragments as they start to break. So maybe that's not the answer. 

I'd start experimenting with the fragments. I'll try to look at it more later and see if I can find anything else.