La Maison has graciously provided a free Mental Ray shader that can be used to output vectors for RE:Vision Effects plugins. The shader was initially developed for XSI as an output shader but it has also been used with Maya and 3D Studio Max. You candownload the free shader here. There is a mappping between the 'Normalize' setting in the La Maison vector shader and the MaxDisplace setting in any of the RE:Vision Effects products. The Normalize setting in the La Maison vector shader maps to the Max Displace value for all RE:Vision Effects products. Adjusting the Normalize setting also results in adjustments to the Max Displace Value. Set the 'Target' value of the lm_2DMV shader to 1 (this essentially means 'make motion vectors that are compatible with RE:Vision Effects' ReelSmart Motion Blur.') Source.