MOTION CAPTURE TECHNOLOGY

By

Arundas M.K

What is motion capture?• Motion capture is defined as the process of

recording the movement of humans, animals, and inanimate objects as 3D data.

• The motion capture is also called Mocap or Performance capture.

History In 1915 Rotoscoping is invented, by Max Fleischer, this is considered as start of Motion Capture. • What is Rotoscoping ? Rotoscoping is an animation technique in which animators trace over footage, frame by frame, for use in live-action and animated films. Originally, recorded live-action film images were projected onto a frosted glass panel and re-drawn by an animator. This projection equipment is called a Rotoscope.

FRAME BY FRAME TRACING OF AN OBJECT (ROTOSCOPING)

Generally motion capture can be classified into three categories :

1. Mechanical motion capture2. The optical motion capture3. The magnetic motion capture

1. MECHANICAL MOTION CAPTURE

o Mechanical motion capture systems directly track body joint angles and are often referred to as exo-skeleton motion capture systems.

o The sensors are attached to the body of performer and each joints are connected to the angular encoder.

o The value of movement of each encoder (rotation etc..) rebuild by a computer that by knowing the relative position encoder can rebuild the movement on the screen using software

o Mechanical motion capture systems are real-time system.

Advantages Offer high precision Do not depend on external factors such

as no. of cameras Computes rotations directly Portable, unlimited range Less expensive Can capture multiple performances

simultaneously No built in positional reference

Disadvantages External structure unwieldy Cannot change the

configuration, i.e., a hand capture can’t be used for an arm

It is complicated to measure the interaction of several exoskeletons.

2.The Optical Motion Captureo The capture is based on

optical shooting several synchronized cameras

o 2to 32 cameras controls by computer

o Operating principle is similar to radar

Working Principle The cameras emits the radiation (usually infra red), reflected by the markers(whose surface is reflected by ultra reflecting material) and then returned to same cameras. These are sensitive to one type of wave length and viewing markers in the form of white spot videos. Checking the information of each camera to determine the position of markers in virtual space.

AdvantagesFreedom of movementHigh quality captureHigh throughput

fast sampling (200 fps at a high resolution)

can capture fast motions can have a large capture space

can capture many markers

Disadvantages•Occlusion, markers are can be hidden from the camera 1.additional performers will increase occlusion

2.may be able to add redundant cameras

• Marker crossover, which marker are you looking at?

• It is more expensive• Extensive post processing (the marker’s have to be located and identified

3.THE MAGNETIC MOTION CAPTURE

Performer wears an array of magnetic receivers which track location with respect to transmitter

Derived from the sensors placed on military aircraft pilots helmet to track the pilot head position and orientation for the helmet-mounted display.

12-20 tracking sensors are placed on a captured subject. Tracking sensors output their translation and orientations. Divide into two groups

1. Direct Currant (DC) : Uses square pulses

2. Alternating Currant (AC) : Uses sin wave pulse

Advantage• No occlusion• Less expensive than optical

motion capture

DISADVANTAGESLimited rangeSensitivity to metalsCannot perform with multiple

actorsCapture volume is limited

Applications Of Motion Capture• Video Games• Film / Animation• Education• Biomechanical analysis etc..

Video Games

Video games often use motion capture to animate athletes, martial artists, and other in-game characters.

Generally there are two main types of 3D character animation used in games:

1. Real-time playback 2. Cinematics Real-time allows the game player to choose from pre-created

moves, thus controlling the character's moves in real-time. Cinematics are the fully rendered 'movies' used for intros and

'cut-scenes'. Often the last part of game production, or a process that is sub-contracted to a separate studio.

Cinematics are generally not essential to game-play, but do add a lot of appeal to the game, and help immensely with story development and mood generation.

Film/Animations Motion capture is being used more and more in

films nowadays  Motion capture based animation is essential for

creating characters that move realistically, in situations that would be impractical or too dangerous for real actors

Some film characters require the use of motion capture, otherwise their animation seems fake

Films that used motion capture technologies are Avatar, The adventures of tintin, The avangers, Hulk, Iron man, Kochadaiiyaan etc…

Avatar Is The One Of The Best Film Ever Used The Motion Capture Technology

In this film photorealistic computer-generated characters, created using motion-capture animation technology

 To achieve the face expressions, actors wore individually made skull caps fitted with a tiny camera positioned in front of the actors' faces

 This method allows the filmmakers to transfer 100% of the actors' physical performances to their digital counterparts

EducationMotion capture training can make a huge difference in an animators training. While access to motion capture is not a substitute for developing good art skills and good traditional character animation abilities, it can go a long way towards making someone more employable. Biomechanical analysisBiomechanical analysis for rehabilitation purposes, relies extensively on motion capture, for its ability to produce repeatable results. Motion capture can be used to measure the extent of a client's disability as well as a client's progress with rehabilitation.

This technology also applicable in scientific research, engineering fields etc…

Advantages Of Motion Capture

More rapid, even real time results can be obtained. In entertainment applications this can reduce the costs of keyframe-based animation

The amount of work does not vary with the complexity or length of the performance to the same degree as when using traditional techniques

Complex movement and realistic physical interactions such as secondary motions, weight and exchange of forces can be easily recreated in a physically accurate manner

The amount of animation data that can be produced within a given time is extremely large when compared to traditional animation techniques

Potential for free software and third party solutions reducing its costs.

Disadvantages Specific hardware and special software programs are

required to obtain and process the data. The cost of the software, equipment and personnel

required can be prohibitive for small productions. The capture system may have specific requirements for

the space it is operated in, depending on camera field of view or magnetic distortion

Movement that does not follow the laws of physics cannot be captured.

If the computer model has different proportions from the capture subject, artifacts may occur. For example, if a cartoon character has large, over-sized hands, these may intersect the character's body if the human performer is not careful with their physical motion.

THANK YOU….