Blackmagic Forum

This is probably super basic but I can't get it to work. I don't do a whole lot of work in Fusion.

I have 4 stacked layers in the edit screen that I created a Fusion comp with. In Fusion I added a tracker node and made a good tracking. All 4 layers are the same movement (with a motorized slider) and I need to window a small square in each of the top 3 layers to put onto the bottom one. I added a rectangle that masks just right but I can't figure out how to apply the tracker node to move the rectangle with the shot.

As with most things Resolve, it's probably something pretty simple.

I am not quite sure what you mean by

I need to window a small square in each of the top 3 layers to put onto the bottom one.

Can you post a screenshot of what you're trying to achieve?

Yeah, I didn't word that very well. So I've got 4 tracks



Each layer has this canister on a different shelf

I need to make it look like there is one on each shelf which works this way.



But when I scrub through, the rectangles don't track:



Again, I'm sure it's something pretty basic. I tried changing the tracker merge to BG only and for some reason it moved the rectangle with the image to the right edge of the screen but it still acts the same.

It's not really basic, because you have different shots that all need to be tracked seperately, but you definitely need to change your setup around.

You're basically trying to create motion control combination shot, right?
It appears that the parts that need to be masked are moving i.e. they're not stationary in the frame.
But you've attached the mask to the MediaIn. Without connecting the rectangle mask to the tracking data, Fusion will mask the MediaIn as is i.e. it doesn't know there's movement, so it doesn't what you want to mask.

And since you have a lateral movement, as far as I can tell from the screenshots, you will need to change the shape of your mask as well (since it won't be a perfect rectangle)

Since the area around the shelfs is black (and the shelf section itself is dark as well) it's probably difficul to track the corners of the shelf, but that is where I'd normally start.

You could also try planar tracking the shelves, position, rotation, scale (and shear?) and see if this will end up with a decent track.

It's still really difficult to tell from the screenshots, but the way you've set up your nodes is wrong /not ideal for what you're trying to achieve. If you can share the shot(s) here or through DM I could take a closer look to see if I could give you some more pointers.

GalinMcMahon wrote: All 4 layers are the same movement (with a motorized slider).

Do all 4 layers actually have the same camera motion, or sort-of have the same motion (and speed)? It looks from your screenshots like the speed isn't the same, which can cause perspective/size issues even if you get the masks right.

If it's exactly the same motion, you might be able to get away with a transfer mode in this case, in Edit, no Fusion required. (I.e. the background of each shelf is uniform black and the foregrounds are bright.) Use Add or Screen or Lighter or whatever looks right.

Or this might be the one situation where you could actually use a Difference Keyer. (Again, if the motion is exactly the same for each shot.)

(Both of the above only work in your situation because you have a background that's dark and nondescript and a foreground whose details are determined by their lights features. It won't work in general.)

Last, you could probably just animate the corners of the masks you've got by hand. (Use a Polygon mask and draw the four corners so you can animate them individually.) Put a keyframe at the beginning and end of the move. Then jump in the middle somewhere -- if it's necessary -- then the middle of each segment. It looks like you have enough room on each shelf so you don't have to track every variation in movement precisely. (And your motorized slider probably creates a fairly smooth motion to begin with.)

If you really need to track -- or want to learn how you'd do this if you had a well-lit bookcase with differentiable texture -- Sander de Regt's advice is spot on.

Thanks for the pointers, guys. I will try these out. Yes, all 4 shots are exact as the cam was on a motorized slider set to loop. They probably looked off because I didn't line the windows up. I was actually pleasantly surprised at how easy it was to alogn the clips...just dropped the opacity of one and nudged the next one into place and on down the line. This is of course just a test shoot. Am going to be replicating several cases at different angles throughout the entire scene. Phew!