[nel piper] "Can I accomplish this with the native motion blur or AE CS3 does not have support for this? Thanks."
AE's motion blur will only affect things that are moving within AE. If the scenes you rendered have motion then that motion is
part of the rendered image and AE has no way to know that it is moving... for all AE knows it could be a locked down image sequence of the mona lisa with no motion at all.
CC Force Motion Blur, on the other hand, can look at the image and try to determine based on previous and next frames where things are moving and then blur those areas directionally... but AE has no way to do this 'natively.'
There is another great plugin that you can use to add motion blur to your scene called ReelSmart Motion Blur (if CC Force Motion Blur isn't providing quality results and you have the $$$). It's available at
http://www.revisionfx.com/products/rsmb/.
It even allows you to render out motion vectors from your 3D package and use those to determine the blurring in AE... which should provide much faster and higher quality results than CC Force Motion Blur (http://www.revisionfx.com/support/faqs/motion_vector_FAQs/motion_vectors/).
Darby EdelenLead DesignerLeft Coast DigitalSanta Cruz, CA