3dsMax EXR motion vectors.
The best option is to use the Motion vector G-buffer in 3dsMax.
X : positive is Right – Negative is Left
Y: positive is Down – Negative is Up
Using the G-buffer fusion in is simple.
In the Loader chose the G-buffer channels for the X and Y velocity.
Then flip the Y channel in the VectorMotionBlur tool to point the vectors in the correct direction.
In Autodeck Composite (toxik)
The Toxik blur tool is actually very cool. The fact that DOF and motion blur are packaged together in one tool is a real advantage over Eyeon Fusion.
This video covers motion vectors in 3dsMax and Autodeck Composite (toxik). But the information can be generically applied. There’s a couple of issues which he fixes in his next video
There’s also a longer in depth look at motion vectors and some fixes if the tools don’t quite behave as they should do.