View Full Version : Partial motion blur ?

09-22-2015, 01:19 PM

Is it possible to only have motion blur on some objects in a scene even if there are lots of other objects moving ?
or do I have to do it in post ?

09-22-2015, 01:22 PM
I would say render out separate passes and compile them in post.

10-14-2015, 02:39 PM
I would like to see if there is a better way to this as well. I currently have a scene that I want just the rotor on a helicopter to have motion blur but not the other objects in the scene.

10-14-2015, 05:36 PM
You could set the Motion Blur amount to very small, say 1%, but have the helicopter rotor move really fast. Or, you could use a high-frequency Oscillator Modifier on the rotor's Heading channel to make it oscillate very quickly around the keyframed motion path.

If the motion of the object you want blurred is consistent (i.e. going in a single direction or a single rotation like the rotor), the high-frequency Oscillator modifier with a low blur amount is probably a general solution, except that the Oscillator modifier doesn't have a inverse of the damping function (i.e. going from small oscillations up to the full oscillations over time). Damping could be used to "turn off" the motion blur at the end of a motion, but starting off is pretty clumsy.

Attached is a sample scene with four red balls, all moving the same speed down the Z axis. Balls 2, 3 and 4 have a high-frequency Oscillator (cycle speed is 1/300th of a second) with increasing Wave sizes (negative wave size to make the blur *behind* the balls) on their Z channels. Because the Motion Blur Amount is set to 1%, Ball #1 doesn't have any (well, much) blur, while Ball 4 has a lot.

The Modifiers are found by pressing the E (Envelope) button on each Ball's Z channel and going to the Modifiers tab in the Graph Editor.


P.S. You could use the same effect on an object with a variable motion by parenting it to a Null, making the Null do the actual motion path, setting the Null to "Align to Path" on all rotation channels, and oscillating the child object on its Z channel.

10-17-2015, 03:22 AM
There was also an internalized script for doing this but I cant remember it now.

Maybe mTp can help on this. are you sure this is the only way mTp? I have used it long time ago myself but cant find it.

10-17-2015, 04:22 AM
not what u r asking 4 but u could try...


10-17-2015, 05:35 PM
Probably this won't help much but I remeber an old free plugin, back in the LW 5.x days, called Independent_Motion_Blur (by Morgwn McCarty) which curiously, still works in last LW versions! but it's 32-bits only.

There's also a 32-bits free plugin called TB_BlurControl (http://web.archive.org/web/20050304123112/home.att.ne.jp/omega/tabo/3dlabo/p_lwp.html) which also works in last LW versions, but again, only x32 version.

Additionally, there's a commercial plugin from Polk Collection by Worley Labs (http://www.worley.com/E/Products/polk/clay.html) (part of the Clay Bonus Collection) which has also an ObjBlur plugin but this works only with objects.