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I'm testing Blender for film/tv work coming from 3dsMax and VRay. (I have 20 years experience in film/tv cgi so you're explanations can go into some detail thanks)

To test the motion blur accuracy I'm trying to replicate this effect of tracers being deformed with high frequency camera shake blur: Tracer blur

In Blender 2.8 (I know its Beta) I added a noise modifier on camera rotation with high frequency settings to match the look of shaky footage. I also managed to create a particle system for the tracers firing (with some difficulty without an on/off emission) The result is this: (Single stream of tracers) enter image description here

And some frames freak out like this: enter image description here

The camera noise doesn't seem to be picked up fully by the blur. I've tried adjusting Camera Noise: Scaling, Amplitude and Depth as well as motion blur parameters: Shutter, Position, Motion blur steps etc but cant get it any closer to the desired result.

Its hard to see in stills but any thoughts from experienced Blender users?

(I really like Blender overall but certainly hope the particle system gets an overhaul. Ideally with nodes)

Cheers,

ED

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    $\begingroup$ Glad you like Blender so far. And "Everything nodes" is a project that is in (early) development right now. (Including Particles) $\endgroup$ – michaelh Mar 17 at 17:10
  • $\begingroup$ Thats great news! $\endgroup$ – EDcase Mar 18 at 15:12
  • $\begingroup$ Maybe related: blender.stackexchange.com/a/41786/1853 $\endgroup$ – cegaton Mar 18 at 17:25
  • $\begingroup$ Yes, could be related but I tried with max steps and it looks the same. $\endgroup$ – EDcase Mar 25 at 19:17
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Welcome to Blender Stackexchange!

This can happen with particles in fast motion. The issue is that they are basically moving too far within the time span of a frame for the calculation to happen correctly. The solution is to add subframes.

subframes

Try to increase this value by one or two. That usually solves it for me. Try more if needed.

Edit after testing the blend file:

Thanks for the blend file. I am seeing the same on the most recent build of 2.8. But I also I tested two things:

  1. Particle movement without Camera-Shake.
  2. NO particle movement but WITH camera shake.

(1) Looks fine, but (2) produces the weird behavior, even without particle movement. This seems like a bug to me, that you probably should report via "Help"-Menu > "Report a bug". (Update your Blender before doing so, because new builds come out every night. - So yours is already WAY out of date.) This seems related, but you are with having the problem with different parameters.

In the meantime here's a possible workaround for your current scene, provided you have access to software with a "force motion blur" effect.

Render with the following changes: 1. No camera shake. 2. A wider image (decrease focal length) 3. Increase the Output Resolution

You can place the result in a Composition with the actual dimensions of your final shot. Move the frame within the composition to fake the camera shake. (Which is essentially the same, since the camera in your blend file only rotates). Apply the "force motion blur" effect.

I know this is not perfect, but merely an idea to get you to the result you want.

Hope this helps.

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  • $\begingroup$ Thanks for your reply Michael but unfortunately that doesn't change anything. I guess its not complete yet. As a side note, Blender is crashing quite often when rendering this scene with both CPU/GPU $\endgroup$ – EDcase Mar 18 at 15:03
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    $\begingroup$ Interesting. Are you using the latest builds? - If possible, you could share a .blend file (blend-exchange.giantcowfilms.com/help) and see what others experience. - I have been working several times with around 1Mio particles, several force fields and collision objects last week. I can't confirm the instability. You can also make simpler versions of your scene and gradually take away movement. (Camera, particle speed, etc.) That could help you isolate the problem. $\endgroup$ – michaelh Mar 18 at 15:25
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    $\begingroup$ I updated my answer. $\endgroup$ – michaelh Mar 27 at 12:34
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    $\begingroup$ Thanks very much Michael for looking into it. I'll update Blender and report if still problematic. $\endgroup$ – EDcase Mar 27 at 20:11
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    $\begingroup$ I updated to latest Blender and the blur does not freak out as it did before but it still does not look right and crashes often (4 times in 100 frames) I'll report a bug on it. Thanks for your help $\endgroup$ – EDcase Mar 29 at 10:37

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