Your browser (Internet Explorer 6) is out of date. It has known security flaws and may not display all features of this and other websites. Learn how to update your browser.

Eye Replacement Test

Alot of pararell work going on at the moment!
Here is a short clip demonstrating the matched rotations of the eyes using trackers and 3d spheres in Nuke. (Track has not yet been completely stabilized + see some problems with the dot removal roto, ..will fix)

Since I want to get spherical distortions of 2d images I am using for the eye effects, I used Nuke’s tracking and 3d system. This is however all thanks to a lot of research and tutorials, since I did not have much former experience in Nuke’s 3d system. –>

In order to get a working 3d scene in Nuke, I began with putting in a Scene-, Cam-, Constant – and ScanlineReder-node. The Scanline taking care of the objects, and the Constant taking care of the format. I connected these to my footage, and then created two spheres, onto which I mapped the 2d images. A reformat node was also used to set the image size so that any images I choose to use wont behave strangely.

To make the sphere rotate and translate correctly with the eye, I first tracked 3 points of the eye, the left corner, the right and the pupil. Some frames had to be tracked manually, like the blink and the headturn, since the track points disappear. 3 points are needed, since the trackers are translated using calculation into rotation.

I used this expression, which is a calculation of rotation in Nuke-terms, using the 3 trackers;

degrees(atan( (parent.Tracker3.track1.y – (parent.Tracker3.track2.y + (parent.Tracker3.track3.y-parent.Tracker3.track2.y)/2 ))/((parent.Tracker3.track3.x-parent.Tracker3.track2.x)/2)))

Using the pupil tracker – the track translation was draged onto the spheres rotate y in the properties windows. The expression above was then added in to the rotate y, which makes the sphere rotate, but in the wrong direction –>
Nuke automatically puts the image on the backside of the sphere (away from the cam) as well as tries to expand the image onto the entire sphere – it becomes distorted. This was solved by changing the u + v extent parameters in the spheres properties, and in an added TransformGeo node, where you can simply transform/rotate/scale the geometry. The TransformGeo node is then connected to the Sphere to make its pivot correct.

To Stabilize the track I used the Curve Editor. The lft and rt trackers were filtered to a smoother movement. The rt trackers keys were also moved or flattened in places where the sphere jumps around a lot due to the tracking. The rt tracker was used because it was the easiest to track during the whole shot.

I then used a Bezier to roto the eye, and animated it using the most stable tracks translate x+y and center x+y. The image was also offset and I needed to insert an expression to get it into the right place, simply using the same numbers already in the translation, only changing the – and the + values.

The 2d image(sphere) was now rotating correctly with the eye. To solve the scaling that occurs throughout the shot I simply put in a transform node with an animated scale value. Added onto this is alot of color correcting and exposure. However, I am thinking to use this “pupil-effect” only in the last frames, as a “finale”. In the rest of the clip I am planning to use entirely black eyes, like the concept. But to do that I only have to remove the pupil effect (I already have a black image behind it) and put on some reflection.

Much work for a 3 second clip, but I want to learn how to use Nuke as much as possible…

Be Sociable, Share!

Leave a comment   You must be logged in to post a comment.