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Question

BIG Problem with motion blur & 3D Tracking in AE!

Forum|Forum|6 years ago
March 26, 2019
3 replies
6487 views

Hey guys,

I was adding 3D models onto 3D-Tracked live footage with a third-party plugin, Element 3D, when I noticed that enabling motion blur in the composition settings and on the Element 3D layer makes the tracking out of sync. Yup, you read me well. If I want to add motion blur to match the camera shutter speed (in my case 1/50 or 180° angle) the whole tracking data is off. When previewing, it looks like the tracking position is off by one frame: the layer lightly "floats" around without sticking to the tracked point. No, moving the layer by one frame forward or backwards doesn't do anything. As soon as you click on the motion blur icon, you can immediately see the layer and the null slightly changing their position, which confirms motion blur is making tracked layers off-track.

I suspect the 3D camera created by the Adobe camera tracker to be part of the cause. But I can't find the root of the problem. Adjusting shutter phase to -1/2 of the angle value (as advised by Adobe) doesn't change anything. Note that I don't have this problem with 2D tracking at all.

I verified the track was off by making a pre-comp of the footage + tracked object and stabilized it with Warp Stabilizer. The track is completely off with motion blur, but perfect without.

Here's what I've done so far, with no luck:

- Re-installing After Effects

- Updating to latest version

- Converting the footage to H.264 MP4 instead of its original XAVC format

- Trying different shutter phase values

- Using Force Motion Blur instead of the standard blur (same thing happens)

Has any of you noticed this problem and/or found a solution? I'd be so grateful if someone had at least a clue of where the issue comes from. Any other suggestions welcome. Thanks in advance!

This topic has been closed for replies.

E

ericmlevy

Inspiring

Does it look better if you set the shutter phase to -90?

That’s how to match the motion blur on most digital cinema cameras. If left to the default, it’ll look kind of like the motion blur is headed in the opposite direction, or off by a frame.

J

julienm44291926Author

Participating Frequently

Hey, I think I've already said that a hundred times, but, I tested pretty much every shutter phase value already, and that it doesn't change anything. Yes, my

shutter speed is 1/50 so a 180° angle. -1/2 of the angle doesn't fix anything in this case..

R

Rick Gerard

Community Expert

I've also said a few times, I'm having no problems like the ones you are having. Make sure AE and Element 3D is up to date, try another shot, follow the workflow I suggested and see what results you are getting.

I did just have one other thought. Are you sure that the footage is not interlaced? That's the only possible thing I can think of that might cause camera tracking to throw some unusual results.

J

julienm44291926Author

Participating Frequently

Any other suggestions guys?

R

Rick Gerard

Community Expert

CC force motion blur is faster and it will probably be good enough. Remember, pixel peeping on a still frame is the wrong way to judge video. You will go nuts. The only real measure of quality is to look at the final render in real time and full size.

I haven't got time to mess with a similar project right now but if the render settings are correct in Element I've never had a problem like the one you are describing. Are you sure you have spent enough time on the Video CoPilot website learning how to use Element 3D? It doesn't take much to foul up the settings.

J

julienm44291926Author

Participating Frequently

I said like a hundred times already that Force motion blur creates exactly the same weird position shift than the comp blur. As if they were working the same way, thus having the same problem... I don't know what to do Rick.. Now I'm stuck with this issue and can't properly work on 3D projects! I think it's maybe on Element 3D's end. Because this doesn't happen with other 3D layers.

R

Rick Gerard

Community Expert

Try adjusting the shutter phase. You can tell AE when in the frame to calculate the blur. I add motion blur to Camera Tracked footage all the time with no problems.

Try pre-composing all the elements that need motion blur and applying Pixel Blur or CC Force Motion blur.

A look at your timeline with the modified properties of the layers giving you problems would help a lot. UU + PrintScreen + paste to the forum is all it takes to share from a Windows machine.

J

julienm44291926Author

Participating Frequently

Hey Rick,

Thank you for the quick reply. As I said in my initial post, I already tried pretty much all the things you suggested. Adjusting shutter phase, making pre-comp + Force Motion Blur, nothing changes. The tracked layer slightly shifts position whenever I enable motion blur, whether it be comb motion blur or CC Force Motion Blur.

Here's a short video of a super basic test project showing you the issue in detail, please watch it closely!

First composition I'm showing is a comp with motion blur turned OFF for the Element 3D solid. Second composition is the same but with motion blur ON.

Both comps contain:

- the tracked footage (25fps, 1/50 shutter speed)

- a solid with E3D opened

- a Null generated from the tracker

- a 3D tracker Camera generated from the tracker

- a group Null controlling the 3D model position.

► In the first comp (0:17 seconds in the video) with MB set to OFF, the track is pretty much seamless; as you can see, the plane model sticks at the top of the sound card, just sitting on top of the red line. (focus your attention on the bottom of the plane model)

► In the second comp, (0:30 seconds in the video) with MB set to ON, the track is completely ruined. The object floats around and doesn't stick to the top of the sound card. At 1:00 in the video, I'm showing you how turning motion blur ON and OFF makes the position of both the 3D object & Null shift in space.

Composition settings are: Shutter angle 180°, Shutter phase -90 (aka the exact settings used for 1/50 shutter speed footage)

Again, making a pre-comp and adding CC Force Motion Blur yields to the exact same issue.

Hope you can figure it out, because I'm lost here. Thank you!

R

Rick Gerard

Community Expert

It looks like the track is off by one frame. I have never seen this before.

Try shifting the footage one frame ahead or behind. I will have to do some tests to see if I can recreate this problem. Did you set an origin and ground plane and make sure that the track was accurate? It's nearly impossible to see if you have a perfect track with a null.

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