Big problem with vectorblur / velocity pass on close objects

[joconnell]

Heya Folks!

I'm doing a shot at the minute with a plane flying through a canyon from the pov of the pilot. The camera is moving independent of the plane since the pilots head is looking in slightly different directions over the shot. I've rendered out a velocity pass for the shot but when we use vector blur in nuke the amount of blur on the cockpit of the plane is huge compared to the amount on the canyon in the background. Since the plane is moving at pretty much the same rate as the camera, I'd expect lots of blur on the background and very little on our plane and this is what happens if I render the shot with proper 3d motion blur.

The shot with proper 3d blur:

https://www.dropbox.com/s/509knoz82u...mblur.jpg?dl=0

The same shot using vector blur - note the bigger amount on the cockpit:

https://www.dropbox.com/s/6mx7kg3jvz...rblur.jpg?dl=0

The nuke script with my velocity settings:

https://www.dropbox.com/s/iz80id57dt...setup.gif?dl=0

The max file that made it:

https://www.dropbox.com/s/s8bovf5aug...issue.zip?dl=0

Any thoughts?

[joconnell]

Hopefully you guys aren't on a bank holiday today, I've a deadline for friday and it'd be great to get some ideas on this!

[Morbid Angel]

Hi Joconnell,

I've looked at your scene. I think there is an issue there for sure. But even if this was working, you probably would get strong motion blur tearing along the cockpit's edges, in this case its best to render cockpit and environment as separate layers and control the motion blur that way.

[joconnell]

Yeah they are render separately for the actual comp, it's just to show the disparity between the two.

[Svetlozar Draganov]

There is something wrong with the velocity of the plane object here, it seems like the camera animation is not taken into account otherwise the velocity of the static objects in the camera view should be zero.
The only workaround that comes to my might right now is to keep the camera and the plane static and move the environment objects instead.

[joconnell]

Yeah I think this one we're going to have to live with - there's probably something wrong with the actual scene itself, it was taken from a maya imported previz and put through god knows how many revisions!