Tracking - refinement doesn't start

Support Compositing and Post Processing
#1

Hi,

I have some weird issues trying to track my footage using a tripod pan shot and one additional helper frame from a different position. I used a Canon 5D with a 75mm lens and there is no visible distortion.
No matter if I enter 50mm or 90mm for focal length, automatic refinement isn’t triggered and the solve error is far too high (>100) and even if i can solve below, 1 the camera movement is plain wrong. I tried manual refinements, the solve error jumps from 43.3 (75.3mm) to 0.555 (75.5mm), or from 78.1 (75.6mm) to 8.3 (80mm)
The solver error between 85-90mm is below 0 but if i control the empties using map reference the angles and distances are very distorted. Enough markers are tracked, I have no more ideas how to solve this.

screenshot (spike where i inserted helper frame)

Screen Shot 2013-02-11 at 11.35.53 AM.jpg1657×971 478 KB

#2

Are you sure you got all the points right? Shouldn’t the one I marked here move the other way, like all the others in the far background?

Screen Shot 2013-02-11 at 11.35.53 AM.png1002×575 647 KB

#3

I’ve tried solving those two frames and apparently got a pretty good solution. (Solve error: 0.1190) Here’s what it looks like if I put a cuboid on top of that building in the middle. (I’ve tracked three points on the roof and oriented the scene accordingly)

frame1.jpg1366×768 290 KB

frame2.jpg1366×768 301 KB

As for the refinement… I used the Canon 5D preset with focal length changed to 75mm. Blender refined that to 65.852mm, which seems reasonable. Lens distortion was calculated as well. I’m attaching the .blend file, feel free to do whatever you want with it. :wink:

If you plan to film it again, I’d suggest trying to fit some of those buildings that appear in the foreground of frame 651 into both of the keyframes. It should make it easier for Blender to solve the camera, as perspective shift would be more apparent.

Attachments

city.blend (518 KB)

#4

Thank you again :slight_smile: When I track those 2 frames or even up to 100 frames, the refinement works, my solve error is 0.1 and the empties match their actual positions on my map reference.
The problem appears, when I track 200 frames or more, although the solve error stays below 1, the angles and the camera position are increasingly distorted. After tracking the pan shot for 500 frames or more everything is distorted and the automatic refinement doesn’t work anymore.

I guess thats due to my blurry footage. On such large scale it seems impossible to track precise enough using 1920x1080.
Anybody else experienced similar effects tracking a 1000+frames pan shot? Is it possible to split my pan shot in different parts, track theses with different helper frames and combine them later?

#5

How far apart are your keyframes for the solve? Try to keep them fairly close (small difference).

#6

I made a separated image from a different position and inserted it in the image sequence of my pan shot, then i used that helper frame and the following frame as keyframes (the two uploaded images i posted).
I attached the .blend and a background-image where i marked the positions of the camera and the tracked buildings

Attachments

cityview.zip (956 KB)