Cycles render crops objects

Hello.
I’ve been rendering animation using Render motion blur, volumetric shader, some compositing, and object deformation blur.

I’ve noticed some test render is weirdly cropped, especially the edges of the objects are gone like the whole objects were not in the right camera view.
I will post a few test renders and a whole blend file.
https://drive.google.com/open?id=1Ahhgs2WRK3Msp0gyeZnjQBUGvlrybnv3

Adjusting render motion blur sometimes works well, but sometimes not. Increasing motion blur shutter from 175 to 200 only worked once or twice. Fewer blur number worked if I make them to 50 or lower. Above 100 didn’t work at all. It only made the whole object’s blur a lot shorter, which I don’t want my scene to be. Adjusting deformation blur did not work at all.

Could anybody tell me what should I adjust? If I can get any solutions, I’d appreciate any help.

Maybe using other computers for a render farm to render them might work? Blender sometimes crashes whenever I try to render this.

Thank you.

SouthernDaikon

Does it happen when rendering single frames also or only with bulk rendering of the complete anim? In the former case, can you tell me a frame number where it happens? A quick test with a few individual frames didn’t show the issue for me.

Hello omgold.

This test render is single frames. I will render the animation to find out if it also happens in animations.

I can’t tell what exact frame it was for these render frames, but when I test render few frames right now, frame 190, frame 194, frame 212, frame 220, frame 222 shows this kind of error.

The head of the objects often gets cropped out.

It happens when there are too many things to do motion blur, I guess.

Thank you.

SouthernDaikon

I’m not sure, but I have a suspicion.

Motion blur see,s not render parts of objects which are before the camera’s ‘near clipping distance’. As your shutter duration is that long, it happens all the time. (You can see that the cutoff changes when changing the near clipping distance).

So inventably there a frames when objects are only half-visible. How to determine whether these contribute clearly enough to the motion blur averaging to be seen in this way is not clear to me. It seems to have something to do with the shutter curve, but I don’t know the internal logic of Blender what is does there.

I understood what you’re trying to say.
As the objects moves fast, it’s going to make frames that the object is not entirely in the camera, therefore ‘clipped objects’ happens.
Motion blur is very long for this scene, so these clipped objects frames will be shown as what they are. Right?
I’ve graphed shutter curve to make invisible to the head of the object. It will make the motion blur seem smaller, but I can adjust overall size of the object.
Thank you!

SouthernDaikon