How can I render particles with motion blur? Render type is set to sphere and the motion blur is set to deformation blur. No matter how high I set the particle blur in der render POP I get no motion blur.

try velocity attribute blur

Thanks, the Velocity Attribute Blur does work.

By the way what does this warning mean?
Warning: topology for /obj/particles: and /obj/particles: doesn't match - no deformation blur will occur

sascha
Thanks, the Velocity Attribute Blur does work.

By the way what does this warning mean?
Warning: topology for /obj/particles: and /obj/particles: doesn't match - no deformation blur will occur

For deformation blur to work you need to have matching topology. (The geometry can be deformed but it needs to have the same point/face counts etc.)

In cases where your particle systems have changing point counts deformation blur won't work.

Is it possible to get non-linear motion blur with particles in Houdini? The velocity attribute blur is just linear and I'm looking more for a radial motion blur.

afaik mantra doesnt support multisegment motion blur like Renderman or MentalRay etc… which is a real bummer.

Imagine a fast spinning wheel… a point on the wheel may be in one position in one frame and a completely different position the next, with uni-segment motionblur the wheels would appear to shrink because the point is being blured in a straight line from one side of the wheel to the next, the problem increases the faster the wheel spins. If the wheel is moving forward as well as spinning it will start doing even weirder things.

With multi-segment motion blur the renderer takes more than one time sample, i.e. it reads the position of the point several times in between frames, thus aproximating a radial blur.

Sesi should really address this in a near future update… I dont know of any renderer apart from mantra where you cant render spinning wheels!

but perhaps this can be manually hacked to mimic multisegment blur, i.e. choose how many segments you want, render the shot multiple times (only for the element that requirers it) , starting from different interframe times then blend them all together…. maybe