HEAD AND BODY REPLACEMENT

Our task was to substitute an actor from a 1976 Hong Kong action film, "Tiger and Crane Fist", (see fig. 1) with a present day actor (Oedekerk) shot against bluescreen

In modern moviemaking, faces and heads of actors are routinely composited over their stunt doubles and even CG stunt doubles are used where it would be too dangerous or impossible to film a scene using human actors. These are not new concepts but what makes �Kung Pow� so unique, is a serious actor is being entirely replaced by a comedic actor who assumes the lead role of the film.

The scene I�d like to demo is a head replacement comp I did when the Chosen One and Ling (woman) are bonding and eventually embrace each other. To meet the length requirements of this magazine article, I cannot accurately explain every step in the compositing of this shot. So, I will gloss over much of the routine setting up of the comp and focus on keying and integration

tricks I used to make this shot even more believable. These areas I will illustrate in more detail will be:

• Combining two Photron Primatte nodes for natural looking edges
• Color correction and concatenation
• Blending hair blacks into the bg with a grad

(All methods and tools mentioned pertain to Shake, unless otherwise specified)

BUILDING THE COMP

The elements that make up this composite originated as Kodak Cineon files which are in 10bit log color space. The first step of this composite was to convert these images to linear color space using the LogLin node.

Step 1)

Removing the head of the original actor - It was necessary to remove the head of the original actor before comping the new head. A painted "clean plate" frame was provided to me by one of our painters using Puffin's Commotion software. This clean frame was matchmoved to the wall of the bg, grain added and articulate roto using RotoShape along the man's collar and

around Ling's head were done to provide garbage mattes. I ran this out as a pre-comp and brought it back into Shake.

Step 2)

Stabilizing the bluescreen fg - Since Steve Oedekerk's performance was very frenetic and animated, stabilizing his head was tricky at times. Chris Watts did a fine job in attaching tracking markers to Steve for this purpose as well as using video previs of scenes from the original film to block out Steve's position and movement.

Step 3)

Combining two Photron Primatte nodes for natural looking edges - For this bluescreen, I got great edges by combining two Primatte pulls. My goal of the first pull was to maintain the softness of his edges, especially his hair. Ensuring that there were subtle grays on his matte edges made it look more natural.

I achieved this by sampling from the bluescreen backing and scrubbing with the background operator in Primatte to make the blacks of the matte black. I did not use the fg operator to scrub over Steve's head key to clean it up and make it all white. Doing so would fatten his matte, resulting in a harder edge and matte line.

To clean up and correct for the holes in his matte and make it perfectly white, I copied and pasted the Primatte I just made, scrubbed the contaminated fg matte areas and made it a hard edged black and white matte (fig. 6). This was used as a HOM (hold out matte) and plugged into the original Primatte's holdout matte input. A DilateErode (fig. 7) was used to shrink this matte slightly, allowing the nice gray edges to appear from the first Primatte pull. The Primatte output is set to onBlack to premultiply the fg against black.