Compositing Hi-Res Stereo Images - Nuke 101: Professional Compositing and Visual Effects - page 366

17. Delete Write1.
The proxy setup is ready. You have pre-rendered proxies for all files, individual
or dual-view streams. Now you can go ahead and create the composite. This is a
very simple composite.
Compositing a Stereo Project
With this composite, the first thing you need to do is deal with the change in length
between the two elements. The background is a 60-frame element, whereas the bullet is a
50-frame element. You have several ways of dealing with this, both creatively and tech-
nically. Let's look at the options.
Retiming elements
Thefirstcreativewaytodealwiththelackofcorrelationbetweenthelengthsofthesetwo
elementsistostretch(slowdown)thebulletelementsoit's60frameslong.Slowingdown
clips means that in-between frames need to be invented. You can do that in three ways:
• Copying adjacent frames.
• Blending adjacent frames.
• Using a technology called Optical Flow to really gauge the movement in adjacent
frames and create in-between frames by moving and warping groups of pixels.
Several different nodes in the Time toolbox deal with timing. You're going to look at two
different options for slowing down elements.
1. Select Read3 and insert an OFlow node after it from the Time toolbox.
The OFlow (optical flow) node generates high-quality retiming operations by
analyzing the movement of all pixels in the frames and then rendering new in-
between images based on that analysis. This node is slow.
Youcanusethisnodeintwodifferentways—eitherbystatingthespeedyouwant
to change to or by keyframing frame locations, which you will do now.
2. In OFlow1's Properties panel, choose Source Frame from the Timing drop-down
menu ( FIGURE 8.35 ).
Figure 8.35. Retiming an element with OFlow.