Presentation FIT'11 Sarfraz

8/3/2019 Presentation FIT'11 Sarfraz

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KuwaitKuwaitUniversitUniversit

Muhammad SarfrazDepartment of Information Science

Kuwait University, Kuwait


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` Motion Data video games, computer animation, animated videos

` Motion tweening is the process of generatingintermediate frames between keyframes tocreate an illusion of motion

` A simple and efficient method of tweening of

motion data for skeletal animations using cubicCardinal spline.


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` Skeleton

` Bone

` Channel or Degree ofFreedom (DOF)

` Frame/Frame-rate


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We can plot the motion data

of a joint for each channel

separately such that:

frame numbers are along

horizontal axis translation or rotation

values are along vertical

axis.

This kind of plot is called

motion curve ofmotion

signal.


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` BVH (Bio Vision Hierarchy) fileformat. This format is simple andsupported by many motioncapture devices and animationprograms.

` A BVH file has two sections: header section describes the initial

hierarchy of the skeleton data section contains motion data.

BVH can store motion for ahierarchical skeleton

` motion of the child bone is directlydependent on the motion of theparent bone.


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` Cardinal spline is a C1

continuous curve.` A Cardinal spline segment, is

defined by four control points,i.e., Pj-1, Pj, Pj+1 and Pj+2.

` The j th segment of Cardinalspline interpolates betweentwo middle control points, i.e.,Pjand Pj+1.

` The end control points, i.e., Pj-1 and Pj+2 are used tocalculate the tangents at Pjand Pj+1.


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` Equation of Cardinal spline forj th segment

2

23

1

23

23

1

23

)(]

)23()2[(]1

)3()2[(

)2()(

!

jiiji

iij

ii

jiiii

PststPst

tstsP

tsts

PstststtQ


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` Motion tweening of a single channel of a joint.

` Objective is to generate smooth animation usin

few keyframes

` Initially the user has to specify the keyframes`All the keyframes and their in-between frames

constitute a complete motion curve of the

channel.


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1. Extract or specify the keyframes.

2. Specify number of in-between frames

between every pair of keyframes.

3. Take each pair of adjacent keyframes asmiddle control points, i.e., Pj and Pj+1 of

Cardinal spline. Take previous and next

keyframes as first and last control points (Pj-1

and Pj+2) respectively.


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4. Obtain the motion tweening data by Cardinal

spline interpolation between every pair of

keyframes Pj and Pj+1.

5. If the result is not satisfactory then go to step1, add more keyframes and repeat the

process.

6. Save the keyframes.


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Environment of Simulation

Hardware Operating System Prog. Language

Inter Core Duo 2.4

GHz

Linux (Ubuntu 10.04

LTS

MATLAB R2010

Animations used in the Simulation

Animation Name Frame Rate (fps) Number of Frames

Ladder-Climb 30 153

Walk-Turn 24 119


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` A simple and efficient method of tweening of

motion data to generate smooth animation

using cubic Cardinal spline.

` The keyframes serve as control points ofCardinal spline to generate in between frames

by interpolation.


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Thanks!

Presentation FIT'11 Sarfraz

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