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Live

7
Maya® LiveTM simplifies the process of matchmoving. Matchmoving is a process where you match the camera or object movement in a live-action shot with the camera in Maya. This subsequently lets you place your 3D objects into live-action footage. Matchmoving is an iterative process where the camera movement for the Maya camera is calculated using processes of tracking and solving.Objects are tracked in the live action scene and a solver then calculates the camera position for a given image. This chapter includes the following lessons:
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Introduction

Lesson 1 Track and solve: Introduction on page 220 Lesson 2 Solving with survey data: Introduction on page 238

About Live
Imagine that you must replace the contents of a live-action shot of a fence with a fence modeledin Maya. In the live-action shot, the camera sweeps around the fence. You can use Live to animate a Maya camera that sweeps around your modeled fence in the same way. When you render the Maya fence from this camera, it will have the same camera perspective as the live-action fence. You can therefore composite them together precisely.

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Live can also match the movement of objects in thelive-action shot. Suppose you want to replace the hat of a moving, live-action person with a cartoon hat created in Maya. You can use Live to create 3D locators that follow the movement of certain points on the live-action hat. You then attach a hat created in Maya to these moving points, so that the rendered Maya hat follows the movements of the live-action person. The steps for matching objectmovement are about the same as matching the camera. To use Live, you do the following major tasks in order:

Setting up
You begin by loading digital images of the live-action shot. In this lesson, you’ll use images scanned from film footage. Images appear on an image plane. This plane is part of the Maya camera. It displays images as part of a background.

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Track
In thistask, you mark a variety of points within the images, such as the center of a flower or a mark on the fence, and have Maya track how they change position from frame to frame.

Solve
In this task, you run a solver program that computes an animated camera, based on the movement of the track points.

Fine Tune
This is an optional task where you can make frame-by-frame adjustments to the cameraposition. (This task is rarely used and is not covered by this lesson.)

Preparing for the lessons
In the following lessons, you will create a match move for live footage of a sweeping shot of a backyard and fence. In the second lesson, you will load a fence created in Maya to evaluate how well the Maya camera movement matches the live-action camera. To ensure the lesson works as described, dothese steps before beginning:

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1 Make sure you understand the basic usage of the animation playback controls. See the chapter entitled “Animation” in Getting Started with Maya to learn about these controls. 2 Select Window > Settings/Preferences > Preferences. Click the Timeline category under Settings and make sure the Playback Speed is set to Play everyframe. Animation plays more accurately with this setting. 3 Locate the Live lesson data on the Maya DVD. It exists on the DVD in this location:
Extras/LiveLessonData

You can work from the DVD directly or copy the directory to the local disk of your choice. If you copy the directory, you’ll need about 300 Mb of disk space. 4 If Live doesn’t appear in the menu set selection menu, select Window >Settings/Preferences > Plug-in Manager. In the Plug-in Manager, locate mayaLive.mll (Windows) and click the loaded checkbox. Wait about 20 seconds for the operation to finish, then close the Plug-in Manager. 5 Select the Live menu set. All instructions in this lesson assume you have the Live menu set selected. 6 Choose Scene > New MatchMove. When you create a new matchmove scene, Live places the...