VFX1 - DD1410: Altar Sequence Rotoing First And Final Shot

The altar sequence has many different elements to it, some of these include rotoing, tracking and keylight.

 The brief for this piece is in the link below:
http://www.darthspockvfx.blogspot.co.uk/2012/10/vfx1-dd1410-brief-01-altar-sequence-001.html

To begin with, lets take a look at the opening sequence:

The video below shows the first shot, frames 0-61 (and a little bit beyond that into the second shot, which is the blue screen bit).

According to the brief, in this first shot the altar and the dragon statue need to be roto'd in case they are to have some sort of effect added to them later along in post-production.

Unlike the car colour correct, this piece has a lot more shots in it, so to make it easier for anything doing work on the footage, it is best to split up each shot. This can be done by creating a backdrop and placing everything from a certain shot in it.

When it comes to rotoing the altar and the dragon, it is best to split the altar up into sections, just in case the director wanted to have a certain effect on a particular part.

The footage also needs to be stabilised. To do this a tracker must be read in. Track from frames 0-61, make sure the tracker is set to stabilise.

Attach the trackers to stand out points on the dragon and altar. In this picture the points that have been chosen are two of the corner points and the ball on the top.

If the tracker jumps at any point or fails to track properly, one can either track it again, or go in and move the track route by hand.

Now that the footage has been stabilised, the tracker should stay with the dragon and altar, at most some tiny adjustments may be needed.

Since the footage has been stabilised, a transform node needs to be read in to zoom in the image. This is because when the footage was stabilised the tracker zoomed in, cutting out the edges, but leaving the viewer the same size. This is represented by a dotted line around the edge.

That is all that needs to be done with the first shot, the last shot (frames 355-449) is very similar.

With this shot, the dragon and altar need to be roto'd again. Unlike the first shot, this one cannot be stabilised because when the girl walks away the shot moves quite a bit, and stabilising cuts out too much of the image (as seen with the dotted line around the viewer in the first shot).

Whilst the camera is following the girl, the altar and dragon move too, so the roto needs to stay with them whilst the footage plays on. To do this a tracker node needs to be read in.

First, like in the first shot, attach the trackers to points on the dragon and altar that stand out.

Then copy across the information from the tracker to the roto. This includes the translate, the rotate, the scale, the scew and the center. 

Now the roto should follow the tracker and keep it with the dragon and the altar.

If the roto doesn't completely follow the track, then one can go through the frames and alter the roto where needed.

The next blog post will include a break down of the use of the keylight node in this piece.