"danyolgiax" <d.o### [at] gmailcom> wrote:
> Hi!
>
> Using motion_blur with a box runs along x axis I've seen this effect is
> bidirectional! I've got a blur in front and at the end of the box!
>
> There's a way to make it uni-directional?
>
> Thanks!
>
> Daniele

Actually motion blur works exactly the way it is supposed to.  In reality,
for an object that is moving at a constant speed, each instance of the
object has equal exposure time and equal weighting in the image.  This may
give the impression that there is blur in front and in back, when really
it's not, the the back of the blur is the object at the opening of the
shutter and the front of the blur is the object at the closing of the
shutter.
What you are assuming that you should see would be for an object that was
moving when the shutter opened, but stopped for some period of time while
the shutter was open, giving that 'position' a greater weight in the
exposure.  To do this (I assume this should work as I haven't actually
played with motion blur in megapov), you would need to apply a function to
the object tranform factor that gives a non-linear movement over the period
of time the blur is calculated.

I hope this made sense to you and was helpful.  Coincidentally, I just came
across an article about this very subject the other day that was very clear
on the reasoning, but for I can't locate it at the moment.

-tgq

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