FAQ/Using Motion Vector Passes
From VFXPedia
There is a difference between vectors accepted by RSMB and generic vectors. RSMB implies R=0.5 G=0.5 means no motion whilst in generic vectors it's R=0 G=0
Standard vectors can be converted to RSMB format by normalising values (divided by a number to get the -0.5..0.5 color range, BC.Gain) and by addition of 0.5 (BC.Brightness=0.5).
To use motion vectors generated by La Maison lm_2Dmv shader with the native Fusion VectorMotionBlur tool,
Connect a Brightness/Contrast right after your vector loader, set Brightness=-0.5.
Increase VectorMotionBlur/Scale significantly (set it about 100 or more)
You can render the Raster Motion channels out of Softimage (Render>Pass Options>Render Channels Output) and use either RSMB or Vector Motion Blur in Fusion.
RSMB needs an additional Brightness/Contrast tool with Brightness=0.5 applied to the vector pass.
Actually, XSI stores inverted motion in X and Y.
So, in the BC tool Gain should be -1.
It's better to separate the objects moving to different directions and at different speed to different layers to blur them separately. It'll help you avoid the edge artifacts.
