Three Dimensional Action Recognition Using Volume Integrals ppt

7/29/2019 Three Dimensional Action Recognition Using Volume Integrals ppt

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THREE DIMENSIONAL

ACTION RECOGNITIONUSING VOLUME

INTEGRALS

AMAL P M

S7 CSE

ROLL NO: 7


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CONTENTS

INTRODUCTION

ACTION RECOGNITION

ACTION REPRESENTATION VOLUME INTEGRAL-PROPOSED DESCRIPTOR

EXPERIMENTAL RESULTS

ADVANTAGES

CONCLUSION

05-03-2013 2Action recognition using Volume Integrals


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INTRODUCTION

Action

o A simple, atomic movement performed by a singleperson.

Action recognitiono A process by which a computer to identify an action

from a video or image scenes

Fields of action recognition

o Video surveillance

o Video analysis

o Human-computer interaction



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ACTION RECOGNITION

Action recognition approaches can divided intotwo main categories,

Holistic approach

o Action as shape varying in time and space.

o E.g. Action recognition using motion historyvolumes.

Sequential approacho Action as a series of individual poses

o E.g. Action recognition using set of visual hulls.



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ACTION REPRESENTATION

The main methods used for 3D action

representation are

o Visual hulls

oMotion history volumes

oWeinland 's descriptor

o Volume integral



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VISUAL HULLS

A voxel is a volume element, representing a valueon a regular grid in three dimensional space.

The set of voxels occupied by an actor is called

visual hull

Using a set of cameras

surrounding actor, find

each voxel is occupied or not. V(x,y,z)=0, i.e. voxel is empty

V(x,y,z)=1 , i.e. voxel is occupied



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VISUAL HULL EXTRACTION

SfS(Shape-from-Silhouette) algorithm is used.

By using background subtraction method.



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VISUAL HULL EXTRACTION

The figure explains set of visual hulls of the

kick action



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MOTION HISTORY VOLUMES(MHV)

It compress a set of visual hull into single

probabilistic representation of the voxels

occupancy.

MHV function is defined by,

( i , t) 1 ,

m a x 0 , , 1 1

where = duration

is the value of voxel in time t.05-03-2013 9Action recognition using Volume Integrals


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MOTION HISTORY VOLUMES (CONT.)

Fig(b) shows the MHV of the action shown in

Fig (a).

Red color represent value near 1 while blue

correspond to values close to 0.



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WEINLANDS DESCRIPTOR

VHs and MHVs are invariant under scaling and

translation, but they are variant under

rotation.

Weinlands descriptor is invariant under

rotation.

Weinlands descriptor achieves rotation

invariance by using the Fourier transform,



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WEINLANDS DESCRIPTOR

Voxels are expressed in a cylindrical

coordinate system.

Figure shows the

Weinland's

descriptor of the

kick action.



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VOLUME INTEGRAL- A NEW DESCRIPTOR

The amount of information obtained in a

voxel-based representation is very high.

Before machine learning we should reduce it

for good performance.

Volume integral is a new descriptor for 3D

action recognition



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VOLUME INTEGRAL

Volume integral is an alternative

representation of a voxel set.

This descriptor transform the actors

volumetric information into two dimensional

representation.

It will significantly reduces the amount of data

of the three dimensional representation.

Yet preserves the most important information.



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VOLUME INTEGRAL

Fig(b)&(d) are volume integral of fig(a)&(c) respectively



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VOLUME INTEGRAL

Defintion of integral of the voxel set as

, 1 (V(,,))=

(,,)

=

,

, 1 (V(, ,))= (, , )

=,

, 1 (V( ,,))=

( , ,)

=

.



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EXPERIMENTAL RESULTS

The results obtained show that the proposed

method is significantly better than Weinlands

in distinguishing actions performed with

different limbs.



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ADVANTAGES

It transforms the volumetric information into atwo dimensional representation

Reduce amount of data

Preserves most important information Action recognition is speed up

Successive rate is high

Descriptor is very sensitive to reflected actions

Same action performed by different limbs can bedifferentiated.



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CONCLUSION

Volume integral only use less amount of space

for store the action representation.

And computational cost required is low.

It can used in applications in which limitations

of computational power and space.

E.g. Mobile devices.



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REFERENCES

Pattern anal applic (2012)-Springer

Three dimensional action recognition using

volume integrals-Luis Daiz Mas, Rafael

Munnoz-Salinas, F J Mandrid-Cuevas, R.

Medina-Carnicer

www . wikipedia . org

www . google . com



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ANY QUESTIONS ???



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THANKS


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