Motion Blur when camera is parented to object?


(tomjelfs) #1

Hi All,

I’ve found that Motion Blur doesn’t work when your camera is parented to an object. Currently I have my camera parented to an object which is following a path and I need it to stay this way but I’m not getting the lovely motion blur. Is this something that I can work around or is there a fix?

Cheers guys

Tom


(shteeve) #2

you can bake the animation to keyframes on the camera as a work around (just confirmed). it’d just become more of a headache to iterate on changes to the parented object/followed path, so you’d best save that step to whenever you’re ready to do a final render.


(tomjelfs) #3

OK thanks, How do I go about that then because I just tried that by choosing Bake Action but that just caused the characters in front of the camera to blur and not the surrounding environment.


(slawek382) #4

You mean motion blur of the object camera is parented to? You do know that you wouldn’t be able to have a motion blur in this situation in real world too. Motion blur occurs when a object is moving in regard to camera. If it’s parented to an object nothing is moving. I just mean it’s not blender bug, but a reflection of realism.


(tomjelfs) #5

OK so a little context is in order I feel.

The rig is Santa’s sleigh and reindeer as per a video I made a few years back, this was rendered in Cycles and the rig works as follows:

• Each Reindeer is parented to it’s corresponding piece of the harness
• Each piece of the harness and the sleigh itself is parented to several vertex of a plane that is split into 5
• The plane has a Curve modifier applied in which a Path is defined
• Finally the Camera is Parented to the sleigh
• The plane is animated in a single axis as far as it needs to go then I can deform the Path to my hearts content and the whole rig follows curves of the Path.

When I bake the Camera’s Action I get the following result in EEVEE 2.8

The same rig set up gets motion blur working in Cycles in 2.79

Here is the Rig

Will a camera’s inherited motion be respected by EEVEE motion blur in future?


(shteeve) #6

ah yeah I see what’s happening. eevee motion blur has no awareness of object motion, only the camera. so everything in the scene will be blurred as though it is static with the camera flying passed it, including the reindeer.

the only other suggestion I can think of is to render a pass of the environment with blur on, and a pass of the sleigh and reindeer with blur off, and composite them. this is definitely an area that could use improvement though. it appears all the eevee render settings are global to the scene; I can’t even see a way to tie them to render layers right now.


(Michael W) #7

Rather than making the camera a child of the object you could try constraining it to the object (copy transforms) or (copy location and copy rotation).
That said I haven’t tested this in eevee. Good luck!


(tomjelfs) #8

That was going to be my next course of action however I feel it’s going to be the same result as parenting.


(tomjelfs) #9

As expected the constraint method did not work.


(tomjelfs) #10

Yeah, at best it seems that the motion blur is just geared up for fly throughs of arch viz scenes, hopefully this is something that is on the pile of jobs that the devs have on the go. The ability to follow an object and that object stay focused is pretty essential I think, also the idea that keyframe data has to be on the camera to get the motion blur seems limiting and I can imagine that this will definitely be looked at. I just wish it was available now, but I guess thems the breaks.


(m9105826) #11

I talked to Clemente about this a while back. He mentioned that there were some limitations to Blender’s scene structure that prevent easy real time motion blur for constrained/patented cameras and object, and for allowing motion blur in the default viewport view. Obviously these issues will have to be fixed before Interactive Mode can happen.