Hi there,
I have serious trouble with particle motion blur in Solaris/Karma. I have no motionblur up to the frame where my particles die. Then the motionblur is literally all over the place. As you can see in the images the life span is set to 2 seconds in a 25fps scene. At exactly frame 50 motion blur goes bonkers.

I made a super simple particle setup to test this and it is 100% repeatable. I tried with caching node and motionblur node in Solaris. I am working on a scene where I set the v from the emitter with a consistent value thoughout the sim - same result.
The setup is really simple and I've rendered scenes with motion blurred particles before. There is no difference between XPU and CPU.

I have tested with build 22.466 and the last daily build. I'm on win 11, 128gig RAM, RTX 5060 16gig.


I'd appreciate any advice or help.

Can at least anyone confirm if this on my side or a Houdini issue?

There are a couple of things going on here.

Try this:

- Disable the motion blur LOP, you don't need it in this case.
- On the Karma rendersettings LOP, go to the Camera Effects tab and set the velocity blur parameter to "velocity blur".
- Go back to OBJ level, select your geo1 container, go to the sampling tab, and Set the Geometry Velocity Blur parameter to "Velocity Blur".

Then try again to render and report back. This works for me, here.

protozoan
There are a couple of things going on here.

Try this:

- Disable the motion blur LOP, you don't need it in this case.
- On the Karma rendersettings LOP, go to the Camera Effects tab and set the velocity blur parameter to "velocity blur".
- Go back to OBJ level, select your geo1 container, go to the sampling tab, and Set the Geometry Velocity Blur parameter to "Velocity Blur".

Then try again to render and report back. This works for me, here.

Thanks, it works. Another Houdini tripwire. The mb going haywire at f 50 still shouldnt happen.
Thanks so much anyway.

As mentioned, you don't need to use the motion blur/cache LOP, you aren't doing deformation blur here.
Make sure you are calculating velocity in SOPs, using point vel SOP, set to center frame, and use "id" attribute.
You can use acceleration blur for this btw, it will be nicer than linear velocity blur.

The reason you get tripped up, is the SOP import is trying to manage you OBJ parameters. So if point v isn't enabled, it's
going not going to make it visible in LOPs.


Cheers,
Lewis

The reason I got tripped is that it looked as if motion blur worked but is broken.
The reason I was using the motion blur node is that I want to copy deformed and animated meshes to the particles. So I still need the node, don't I?
Wouldn't it be nice if there was just one consistent method for motion blur? It's never the easy way with Houdini...
But again, Thanks.