Motion blur problem

Repost from my thread in WIP.

I have a small problem with what I believe is the motion blur.

This is 3 frames in a row from the animation. As you can see in the middle, the right chain gets very “blurred”.

I have the same problem the last 90 frames or so, but then 2 of the chains gets like that, even though theres less motion by the camera, and the chains are static by then.

I have curve modifiers that’s driving the chains. And cloth simulations thats driving the curve.

If I turn the motion blur off, the problem disappears.

Hope someone knows what the problem is, I’m nearly finished and hoping to render out the final animation today!


Going to bump this.

I would be extreamly greatful if someone knows what the problem is!

Already rendered the final animation and rendered the specific frames with the problem without motion blur.

Although it looks alright, I would want to fix this so I know how to do in the future!

There is a known bug with motion blur combined with rigid body physics in 2.72, some frames just don’t render right. I know that for that issue rendering with 2.71 works. It’s possible this is a different version of that same physics/motion blur bug. Give 2.71 a shot, at the very least it’s a painless try.

Thank you Photox!

Didn’t really think of that! I will try it, only need a couple frames so it’s no big deal! :slight_smile:

Yeah, post back if that fixes it. If that does solve it, you might want to file a bug report with the blend.

I’m sad to say it did not work.

How do I file a bug report with the blend file?

Hmm, back to drawing board. If you want to post the packed blend we can look at it, if it’s not something you can share publicly you could pm it.

I wouldn’t file a bug report yet, until we rule out settings.

Also I am not 100% what the issue is. You say the middle image is blurred, but that it to be expected from motion blur. Also have you actually rendered it out out to video and watched it. Sometimes still frames of blur can look odd, but they look perfect when viewed as video. Perhaps elaborate a little on the issue.

Yes, I did not explain as well as I could I guess! I will see if I can get the .blend to a manageble size. The only thing you really would need is the chains and lightning etc.

I have watched it after I rendered it out to a video. It’s actually more noticeble then.

The right chain at the middle picture (there’s more frames with the same problem) gets like “super motion blur” at only a few selected frames. Same frames every time I re-render. As you can see, the difference in the position of the chain is not at all much between the frames.

If it would be motion blur, the left would also look like that.

But the problem is only visible when having motion blur, so I’m a bit confused of what the problem could be.

Maybe blurred is the wrong word to choose, it gets very transparent.

Hard to say. I’m a bit puzzled, you say the chain has a curve modifier, that makes sense, but then you say the curve is somehow parented to a cloth sim, that I’m not visualizing. All I can think of is that the curve has empty hooks, and the hooks are vertex parented to 3 verts on a cloth sim mesh. It seems unusual. Dropbox a simplified version.

hey there.
just found this thread.

i have kind of the same problem. it’s the curve deform modifier that causes the motion blur to blur in the wrong direction.
i have a tube that follows and deforms along a curve, and the motion blur uses the direction of the tube as if has not the modifier applied.

any workaround here or a solution anyone?

okay, just found out that turning off the auto smooth option gets rid of the problem, but also renders way slower then.

reported a bug to blender devs.


You are correct. The curve has empty hooks that is parented to the vertex on a clot sim. It was the best alternative I could come up with my basic knowledge of blender. I will upload a simplified version today!

Edit: Here it is:

Frame 147 is the first time I encounter the problem on the right chain. It gets more visible if you have a white backround.

Yea this sucks. I’ve just run into this issue on one of my own projects as well. Only thing that seems to work is I wrote a script that bakes the object’s translation and rotation data into animation curves, and disables the rigid bodies (mine uses rigid bodies…). It’s really slow though… :frowning: (100 frame animation (*10 sub-steps per frame) with about 2,000 objects takes a good 5 minutes to “bake”)

This method will only work if your chain is made up of links, and each link is it’s own object. (ie it won’t work if the chain is being deformed). Also, just to be safe, make a backup of your scene. If this is the case, I’d be happy to post the code here. :slight_smile: