I've got 10000 spheres copied to particles with very high velocity (5000 along y), when I try to render with motion blur using velocity blur everything comes to standstill, using 2gigs of ram and swapping to disk and still at first bucket after 2 hours. Now when I turn on transformation blur no blur at all, also when I animate my camera position I still get no motion blur.

Anybody any tips on how to achieve a rendering with motion blur at acceptable times or how I can set up ‘in camera blur’?

Many thanks

Andre

PS. Can't change the sphere/pop setup and running Houdini 6.0 on Linux.

I've got 10000 spheres copied to particles with very high velocity (5000 along y), when I try to render with motion blur using velocity blur everything comes to standstill, using 2gigs of ram and swapping to disk and still at first bucket after 2 hours. Now when I turn on transformation blur no blur at all, also when I animate my camera position I still get no motion blur.

You'd expect that. Velocity blur gives you a more accurate looking mblur because it's based on particle direction, but it can't run at the same time as transform blur(e.g. moving cam). You can use deform blur and both will be in there, however you need to rethink your particle system and ensure that all particle birthing is done at the beginning and then never changes(i.e. you have all 10000 particles offscreen and the simply move through - no more birthing or death). This ensures the point count remains the same, which is required for transform/deform mblur.

Anybody any tips on how to achieve a rendering with motion blur at acceptable times or how I can set up ‘in camera blur’?
…
PS. Can't change the sphere/pop setup

Well, those two statements may be mutually exclusive. I'm not sure why you can't change the sphere copy, but that's a number 1 with a bullet affect on speed/memory problems(you should try to render particles with optimized render appearances, rather than spheres). Also, as usual, it's often about “how can I hack this shot?”, as opposed to throwing in all those spheres with huge amounts of mblur. But apart from all that, things moving *so* fast can usually be faked in some way. Are they only moving in Y? Are there many layers? I would break things out to do one thing in the distance and something else close up…

Just some thoughts…

Cheers,

J.C.

John,
Thanks for your reply. Yes I did ensure that I only have 10k particles and no more are birthed and they are only moving in Y.

As for the setup it is for testing purposes not for a shot. Otherwise I could just do the mblur in COP's afterwards and could instance my sphere, you know really streamline the scene.

Cheers

Andre

You could also output your velocity to a deep raster channel and use that for your blur in your comp. But that is not what you're testing.

athomas
I've got 10000 spheres copied to particles with very high velocity (5000 along y), when I try to render with motion blur using velocity blur everything comes to standstill, using 2gigs of ram and swapping to disk and still at first bucket after 2 hours. Now when I turn on transformation blur no blur at all, also when I animate my camera position I still get no motion blur.

Anybody any tips on how to achieve a rendering with motion blur at acceptable times or how I can set up ‘in camera blur’?

The cost of motion blur is very much related to how much screen space the blur is covering. So, “5000 in Y” might be a lot, or very little if the size of your scene is in the millions.

Also, check your camera's shutter, and take it off the default 1.0 if you haven't already (.5 is what the default should be, IMO).

Then, try one particle, then two, then 10, then 100, and so on, to figure out how far you can take it. But, for example, if you have a ton of particles zooming by, starting offscreen, and going offscreen on the other side all in the span of a single frame, you're going to be there a while!

– Antoine