Motion vector pass for pyro

[trishit]

Hi Guys

I faced a problem recently while rendering out my motion vector pass for pyro.
I had cached out my pyro sim with a vel multiplier through volume vop as I did not want to change the shutter offset value more than 1 as it was giving me some artifacts.

While rendering the motion blur what I get is fine as I have already a premultiplied velocity in my pyro cache.
the issue is when I try to get a motion vector in my aov mantra doesnot show any info when I switch off the allow image motion blur option.When I keep it on then I get to see the aov. Strangely if I keep the allow image motion blur option switched off and put a value of shutter offset 1.1 then mantra starts showing the aov.

I fail to understand this as I had already had vel multipler vop while caching it out and thus I dont need any shutter offset value(its at default value 1).

NOTE: I tried h14 and h16 all same results.(just thought maybe due to some bug issue)

Please advice.