CS426 Lecture 16 MoCap

Flashcards generated from lecture notes on Motion Capture (MoCap).

Who was hired to photograph a horse galloping?

Edward Muybridge was hired by Leland Stanford to photograph a horse galloping to prove that all four feet are off the ground simultaneously at one point.

What was the name of the report published that detailed animal and human locomotion?

Animal Locomotion, published in 1887, was the report from Edward Muybridge's study of animal and human locomotion.

Name the components or devices that might be included in a Gesture Controlled User Interface.

Components may include a camera, speaker, screen, PC, PDA/Phone, database, dataglove, microphone, motion sensor, and RF link.

What three measurements are required for the recognition of a hand gesture?

Shape of the hand, location of hand in relation to body, and motion of the hand.

What Patent Number is associated with the structured light source used in the Kinect Sensor / Primesense?

US2010/0118123

What are the main components of the structured light source (Kinect Sensor / Primesense)?

IR Projector, RGB Camera, and IR Camera.

How does the Kinect Sensor (Ver 2) measure depth?

By measuring the delay between emitted and reflected modulated IR light using two sub-pixels, with the range proportional to the charge ratio between the sub-pixels.

What visual phenomenon allows the estimation of object distances in stereo vision?

Parallax."

What is the correspondence problem in stereo vision?

Finding the common point in both images.

What is the role of epipolar geometry in stereo vision?

It reduces the search space from 2D to 1D, helping solve the correspondence problem.

What is the purpose of calibrating camera pairs in a camera-based human motion tracking system?

To allow features within the field of view of any two cameras to be tracked in three dimensions.

Name three sensors used in inertial MoCap suits.

Accelerometers, magnetometers, and gyroscopes.

What does INS stand for and what does an inertial navigation system provide?

Inertial Navigation System. It provides position, velocities, and attitude of a vehicle.

How can position be obtained using accelerometers?

By double integration of accelerometer output

How can orientation be obtained using gyroscopes?

By single integration of gyroscope output.

What additional sensor is required to determine Yaw when using accelerometers for orientation sensing?

A magnetic compass.

How does a gyroscope tend to resist changes to its orientation?

Due to the angular momentum of the wheel.

What three measures can a sensor fusion algorithm use to provide 3D driftless orientation?

gyroscopes, accelerometers and 3D magnetometer.

In the description of bones and joints for character animation, what is typically taken as the origin of the bone description?

The hip/pelvis

Define Degrees of Freedom (F) is the context of animation.

Number of independent variables which must be specified in order to locate the elements of a link relative to one another.

What is rigging when 3D modelling?

Setting up the relationship between the model and bones (skeleton/armature).

What is simple skinning animation?

A group of vertices (belonging to a bone) move as if belonging to a solid object. The surface (triangles) attached to vertices retain their connectivity.

Give an example of a deformable model animation.

Dude.fbx

What is a BVH file?

Biovision hierarchical data.

What does the MOTION section of a BVH file contain?

Channel information for each time step.