IMD 4003: Match-Moving I

For IMD 4003: Computer Animation, taught by Chris Joslin

Contents

1. 1. Six Step Match-Moving Process
   1. Step 1. Evaluate Source Footage
   2. Step 2. Apply Additional Information
   3. Step 3. Define the Camera
   4. Step 4. Set Fitting and Layout
   5. Step 5. Testing the Match Move
   6. Step 6. Deliver the Scene
2. 2. Six Step Perspective Matching Process
   1. Step 1. Gather Data
   2. Step 2. Setting up the Camera
   3. Step 3. Add Rough Geometry
   4. Step 4. Create the Camera Rig
   5. Step 5. Evaluate and Adjust Camera
   6. Step 6. Finalize

1. Six Step Match-Moving Process

Match Moving: the process of taking a 2D image (single or sequence) and placing 3D objects, 3D lights and 3D cameras into it.

Step 1. Evaluate Source Footage

You need to know the following:

• Camera movement: how it's moving and its speed.
• Object visibility: what objects are in the scene, are the tracking markers there and when are they occluded.
• Format of the footage (ex. film or digital - graininess tends to be a problem).
• 3D Object: where it's going to go and how much accuracy you need.
• Final use: how will the footage be used and by whom.

Step 2. Apply Additional Information

You'll be using additional information to help you with the Match Move. This will come from the following:

• Camera Information: focal length, aperture, film time (length of shot).
• Survey Data: a detailed measurement of the set.
• Set Measurements: camera height, focus distance and real-lie scene object measurements.

Step 3. Define the Camera

You need to define the internal and external parameters of the camera using the software. There are 2 ways to do this:

1. Manual: this involves perspective matching and hand-tracking. This method is time-consuming because it's guesswork.
2. Automagic: software uses Photogrammetry (explained in the next lecture) to...
   1. Track the 2D features in the sequence;
   2. Analyze the movements of the 2D features using tracking markers (that you can set yourself); and finally
   3. Generate animated cameras and 3D tracking markers.
   This is the easiest method to use because it's automagic.

Step 4. Set Fitting and Layout

In this stage, you want to determine the spatial layout of the environment. You need to know:

• Amount of environment you need to reproduce which depends on what you're putting into the footage.

Step 5. Testing the Match Move

In this stage, you can composite a 3D Proxy Object (which is basically a crappy reference object) over the image sequence. Use a checkerboard texture to check for 3D "slippage".

Step 6. Deliver the Scene

You need to deliver your final scene to other people in the production pipeline. Some considerations you should take into account are the orientation and scale of the scene, objects that will need to be put into the scene, naming conventions, format, etc.

2. Six Step Perspective Matching Process

Perspective Matching: matching the perspective of a single image to a 3D scene you want to create.
This process is about exactly the same as the Match-Moving Process but with slight tweaks. Go through the tutorial, T07 - Match-Moving and it basically outlines everything here.

Step 1. Gather Data

There are 3 things you will likely need to guess: camera Focal Length, Set Measurements and Distance of Objects from camera. You can generally make a pretty good educated guess about all of them and the tweak the settings later in the process.

Step 2. Setting up the Camera

You do 3 things in this stage:

1. Evaluate the Scene: determine where the 3D object will go, the camera's position in the scene and position of the objects already in the scene.
2. Create a Camera with an Image Plane as the backdrop.
3. Estimate the Focal Length, Aperture and Height of Camera (yes, this is exactly like the last step).

Step 3. Add Rough Geometry

Place geometry with approximately correct dimensions into your scene. These objects represent real-life scene objects. Make sure they're approximately the right distance from the camera.

Step 4. Create the Camera Rig

Here is where we adjust the camera to view the scene better:

• Create a null Locator and snap it to a good rotational point in the scene;
• Make the Camera the child of the Locator;
• Use the Locator to rotate the camera into position;

Step 5. Evaluate and Adjust Camera

• Adjust the Focal Length: longer (bigger) lenses look flat whereas wide (smaller) lenses look distorted.
• Adjust the Scale and Position of the 3D Objects.

Step 6. Finalize

Use the objects in the scene to cast shadows and provide occlusion for your artificially placed 3D object.

Celebrate with a beer.