🚀 go-pugleaf

steve gowin wrote:
> 
> 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.

Hello!  Folks, it doesn't need to be this hard.  Photographic
sequences where the moving subject is still wrt the frame and
the background/wheels/etc. blur are done where the photographer
tracks the object with the camera and then snaps the picture.
Because the camera is tracking to the object, it remains still
wrt the frame of the picture.  The background will blur because
the camera is panning against the background while following the
object.  The wheels will blur because they're moving.

Soooo, do the following:


1. Set up a scene with a car, a background image mapped onto an
object, a road in the foreground, and a car on the road.

2. animate the car moving through the scene, rotating the wheels
by however fast they need to go (roughly) to rotate for the car's
movement.

3. target the camera to the car.

4. render a frame where the motion of the car is essentially
perpendicular to the line drawn from the camera to the car.  If
the car's movement is not perpendicular, there will be some slight
perceived rotation and some minor blurring to the car.

IT'S JUST THAT SIMPLE!!!

---Prem
perpendicular