Compositing Project 5

01 – Camera Stabilization

This is a simple exercise where we simply stabilize a shaky camera. This is a minimal node tree for just stabilization:

The stabilize node only moves the frames so that they will remain as close to the tracked points original locations as possible so we need the Window (Crop works just as well) node to cut out the excess to give the illusion of a stable camera. Unfortunately we have no choice but to lose some of the original image as a trade off.

Here is an overview of the tracked nodes:

I chose these points so i would have two in the foreground and one in the background, creating a triangle in perspective. Once you have tracked your points, you need to activate “applyTransformation” in the properties of the Stabilization node in order for it to move the camera.

The result:

02 – Skilift Tracking

Now we try to matchmove a composited element with a moving live action element:

This is our node tree:

The tracking in this shot is much more difficult since we’re tracking a foreground skilift that crosses the path of other elements twice, muddling the tracker. To amend this, we can allow it to reach the end of its camera presence and delete the errant frames and allow shake to interpolate the motion in the problem areas. However, we can also see that as our skilift leaves the camera, the tracker refuses to move and follow it off the camera.

This can be addressed in two ways: we can manually keyframe the tracking at a later frame and use the curve editor to try to match the interpolation line to the video. Or, we can use the offset feature of tracking and tracking something else on the same object. I went with the former for this since at the time I was not aware of the alternative.

I tracked both sides of the lift as well as used an average of the two for this result:

Notice in this one the tracking area is very large. At this time I also had not realized the area is per frame, not across the whole duration of the video. Keeping this area as small as possible makes your tracks even easier to be accurate.

Once you use a move node to position yourself properly and try to correct color, you can tell the MatchMove node to applyTransformation and see that we still need to mask the hands so that they don’t show through the ski lift:

Here I simply make a rotoshape and animate it along with the ski lift to mask my hands:

Finally, our original color key was bad because of our source video so there’s a lot of flickering in the arms and legs so I over’ed several more rotoshapes of appropriate color to hide them.

The result:

03 – Camera Matchmove

Here we composite a cg element on top of a moving camera.

Node Tree:

Similar process to the last one, we find several good points on the source and track:

Position and MatchMove the turret and check the perspective. Relatively simple now that we’re used to it after the last composite. However, now we need to take care of the shadow from the tree so we create a DropShadow and Over it on top of the original to create a shade. The DropShadow is a little smaller so we tweak its size with a DilateErode node so it completely covers the original. Looks plausible now, but boring. We notice several patches of light that shine through the tree’s leaves so we mimic it with a RotoShape and an Outside node to create several holes in the DropShadow:

We add some blur to the rotoshape to soften the edges but still see that its too smooth and perfect compared to the surroundings so we add a pixelize to it as well. Looking at it, the light difference is too great so we also throw in a Fade node on the RotoShape to dim the bright areas a little further.

The result: