what is this white spot?

[chow choppe]

Hi everyone

 

We are rendering an animation and in some of the shots we are getting a bold white spot in the glass and moves across the glass for some frames as if its sun.

 

 

 

But we are just using direct light for sun source and not vray sphere light and to my knowledge direct light is default invisible.

i tried a few things and was able to get rid of the problem but i dont know what solved the problem actually. heres what i did.

 

My glass was using a highlight value of .97, so i made it 1. and bingo! it solved the problem.

Then to find out whether it was the actual problem i made it .97 I turned off specular for my direct light. now again i don't get that white spot

now the weird part comes

i made my settings back to what was giving me white spots. but now i dont get a white spot . Now i am worried that if i render the animation i might get that white spot in some other frames and that will waste a lot of my time after i get to know after endering all frames. is there any way to find a proper fix to this before rendering the complete animation.

 

thanks