🚀 go-pugleaf

andy@crazybe.demon.co.uk (Andrew Barnett) wrote:

>Hi All, just a silly little question

>I'm trying to do an effect I saw in a car advert poster, the car it self
>was not blured but the wheels were as it was speeding along. Who do I get
>the wheels to blur but not the whole car/ picture ?

Set up your scene: car ,wheels and everything else, as you would
normally.  Render the car first without the wheels (or the wheels set
at 100 percent transparency) then re-render the scene with the wheels
only and motion blur on. The trick is to save alphas when rendering
the wheels, then composite them with the original. Also, if some of
the wheels are being occluded by the car or other objects, make sure
you include those objects when rendering the wheels but set their
surface attributes to:
	color = black as black can be 
	luminosity =100 percent
	Diffuse = 0 percent
This will effectively matte out the background wheels, 
(hopefully) achieving the effect you want. I haven't tried doing this
but it should work assuming the motion blur effect is saved with the
alphas.