Week06 Lecture

7/30/2019 Week06 Lecture

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Topic 5.

Some extra effects

Sampling, Aliasing , Anti-aliasing Al


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Manifestations of Aliasing


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Supersampling


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No Antialiasing


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Antialiasing with 16 samples per pixel


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Topic 6.

Computer Animation Keyframe animation

Forward kinematics

Inverse kinematics Motion capture


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Keyframe Animation

Basic Idea: Define model parameter at key frames

and interpolate (often using cubic splines)


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Designing Plausible Motions

It is quite easy to end up with a physically impossible

motion


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Designing Plausible Motions

It is quite easy to end up with a physically impossible

motion =>

add a sufficient # of keyframes to constrain the motion

sufficiently


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Keyframe Animation

Pros: Very expressive

Animator has full control of animation

Cons:

Very labor intensive

Difficult to create convincing physical realism

Used for practically anything except complex

physical simulations (smoke, water, etc.)


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Topic 6.

Computer Animation Keyframe animation

Forward kinematics



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Specifying & Interpolating Keyframes

Instead of painstakingly specifying every little

motion, specify very few keyframes (or just initial &

goal)

Interpolations are done automatically


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Animating Articulated Structures

Forward Kinematics: Specify how joints should move

Inverse Kinematics:

Specify where character should go, then

deduce joint motion

Motion capture: Record motions of real people/objects, then

transfer to digital characters


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Forward Kinematics

Goals: Determine space of possible motions

Parameterize it

Establish a mapping from joint angles to positions


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Forward Kinematics

Goals: Determine space of possible motions

Parameterize it

Establish a mapping from joint angles to positions


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End-Effector Space (aka Configuration

Space)

What is the set of points that are reachable by this

2-axis structure?


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Space)


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Space)


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Space)


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Motion in Joint Space vs. Configuration

Space


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Motion in Joint Space vs. Configuration

Space


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Key-Framing with Forward Kinematics


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Pros: Very easy to specify & implement

Cons:

Often we care more about where the charactershould go, not how to get there

Very hard to know how to move joints of a

complicated figure in order to get the desired pose(esp. in presence of obstacles)


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Topic 6.

Computer Animation

Keyframe animation

Forward kinematics



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Key-Framing with Inverse Kinematics


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Inverse Kinematics: Difficulties


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Numerical Inverse Kinematics


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Numerical Inverse Kinematics


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Inverse Kinematics & the Jacobian


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Inverse Kinematics & the Jacobian


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Inverse Kinematics Using the Jacobian


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Inverse Kinematics Using the Jacobian


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Topic 6.

Computer Animation

Keyframe animation

Forward kinematics



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Marker Based Motion Capture


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