Need help with 4 points tracking

[Anonymous]

Hi everyone,

I just started learning flame and I have a question regarding 4 points tracking. I’m trying to composite a computer screen with 4 point tracking, but when I finished analysing the tracker the image came out smaller than the monitor.
I’m pretty sure this happened due to the tracking points are not exacly on the coner of the monitor, and the corners of the image follow the tracking points.
My question is what would be the best way to fix this problem? Do I adjust the axis of the tracked image after? or I adjust the image before the tracking process?
I tried adjusting the bilinear image before tracking it, but it seems the tracker overwrite the adjustment I did on the image.
I appreciate any help and opinion… thanks in advance…

[Scott]

Try to adjust the offset. If you just need scale the image up a little to match the computer monitor the offset should work fine.

md

[Peter DeMund]

so I Assume that I need to adjust the offset before I perform the tracking right? thanks…

[Scott]

No, the offset is like a 2nd axis on that image. Apply the tracker then adjust the offset until the image fits.

md

[Peter DeMund]

another beginner question… how do I add an offset node/axis to my tracked image? tanks…

[abhishek]

what Martincito said 🙂

[filip]

Go to the animation menu and under your bilinear surface you’ll find the offsets (with S, no offset) form there you can move the corner without affecting the tracking

[Peter DeMund]

thanks Martincito…. the offset inside the animation module works…
now another question…. how would you clean up the edges of the tracked image… what’s the trick to have a soft edge? i was thinking applying a matte with soft edge, would that work?

[burhan]

You could go into the keyer and create a gmask and feather the edges by using
and offset to soften the edges. YOu can also add a source node and seperate the front
so you can adjust the front inside the matte area.

[McArdell]

I rarely us a 4 pt tracker for a monitor comp… you are dependent on getting 4 really good tracks and then dealing with the offsets and issues when one or more corner leaves the screen. I usually do a one or two point track (depending on shot) and use a bicubic or bilnear (depending on screen) to tweak in.

I have used 4pt tracks and had them work fine, I just find unless I need them they can be more finicky.

Jeff

[Peter DeMund]

neonmarg,

thanks for your input. I will definitly give this one a try. My question is, do you resize and positioned the image where you want then track it with 2 points tracking?
Can you please elaborate a bit if you don’t mind? Thanks…

[McArdell]

Let me walk thru a 1 pt track. Add an image (let’s use bicubic) in action. Add another axis and parent so it reads:
axis1 to
axis2 to
image

Track Axis 1 to your best tracking point in the monitor. When done, use Axis 2 to position the image where you want it. If you need to skew the image you can use the bucubic handles to position as desired. Same layout would apply to 2 pt tracking if you needed scaling and/or rotation.

There are many ways to do this in Flame. This is probably what I would try first folllowed (depending on the scene) with trying a camera track.

Jeff

[guillem ramisa]

And to finish things off. When your track fits, either with a 4 point or a regular 2 point (I use that one the most, it’s faster). Then it’s time to make things look nicer. First look if the image needs defocus, if so add some blur. Then I often make a copy of the tracked image with a circular gmask and put that on top of the original and add some cc to darken the edges to make it blend in better. On top of this add the background layer in screen mode to get back the reflections on the TV. If you want to adjust transparency or enhance the reflection you’ll need to cc the image. And finally put the background image on top with a gmask for the edge of the TV. You might want to do this in a different action node with filtering turned off to avoid degrading the whole background image.

[pixelmonk]

As Jeff quite rightly says, experience has taught me that a 2 point track with a bilnear, or bicubic (if it’s an old style TV with curvature) will give a better result, also less room for tracker errors.
Once you have your 2 point track, just go and tweak your bilinear/bicubic and Voila!

Paul

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