In order to obtain the Motion Blur effect, we need to create a Motion Vector Pass. At least, you have to create a colorPass and an other Pass that is fast to be rendered out, something like an AmbientOcclusionPass. Open the Render Setting (mental ray), go into the Passes Tab and create a 2D Motion Vector Pass. Associate it to the fastest render layer you have, like the occlusion Pass.
At this point, if you try to render out your passes, you'll notice that the pass with the Motion Vector Pass is slightly late (0.2 frames) w.r.t. the other passes. In order to fix this, you'll need to change some setting into all the passes that are not associated with the Motion Vector Pass.
Go into the Features Tab, set the Motion Blur to "No Deformation" (you're activating the Motion Blur). Then go into the Quality Tab, set the Motion Blut to "No Deformation" and set to zero Shutter Open and Shutter Close. Open FrameBuffer section and set Data Type to RGBA (Float) 4x32 Bit.
BE SURE that the Pass associated with the Motion Pass Vector has NOT the Motion Blur on. (IMPORTANT!!!)
Most important thing, in order to preserve much information as possible, you NEED to render out ALL your passes into the EXR format.
N.B. in order to obtain also the Motion Vector Pass separately from the other passes, you need to set into the Render Setting the File Name Prefix in such a way that Maya renders out files titled both the renderLayer (e.g. OcclusionPass) and the RenderPass associated (e.g. 2D Motion Vector Pass), as shown into the following image.
You're now ready to use Autodesk Composite in order to obtain the Motion Blur Effect!
At this point, if you try to render out your passes, you'll notice that the pass with the Motion Vector Pass is slightly late (0.2 frames) w.r.t. the other passes. In order to fix this, you'll need to change some setting into all the passes that are not associated with the Motion Vector Pass.
Go into the Features Tab, set the Motion Blur to "No Deformation" (you're activating the Motion Blur). Then go into the Quality Tab, set the Motion Blut to "No Deformation" and set to zero Shutter Open and Shutter Close. Open FrameBuffer section and set Data Type to RGBA (Float) 4x32 Bit.
BE SURE that the Pass associated with the Motion Pass Vector has NOT the Motion Blur on. (IMPORTANT!!!)
Most important thing, in order to preserve much information as possible, you NEED to render out ALL your passes into the EXR format.
N.B. in order to obtain also the Motion Vector Pass separately from the other passes, you need to set into the Render Setting the File Name Prefix in such a way that Maya renders out files titled both the renderLayer (e.g. OcclusionPass) and the RenderPass associated (e.g. 2D Motion Vector Pass), as shown into the following image.
You're now ready to use Autodesk Composite in order to obtain the Motion Blur Effect!