elastic facial caricature warping lyndsey clarke cslyndsey ~ phd student ~ ~ university of wales...

Elastic Facial Caricature Warping

Lyndsey Clarke

http://cs.swan.ac.uk/~cslyndsey

~ PhD Student ~~ University of Wales Swansea ~

Introduction


• ‘Elastic Facial Caricature Warping’ is a computer graphics technique that I have developed during my first year as a PhD student.

• The project began life as my undergraduate dissertation.

• A short paper on this technique has been published in Eurographics 2006 Short Papers proceedings, and a poster was presented at the conference last month.

• The two main themes that have been developed are:– Caricaturisation– Beautification

• This talk aims to explain the paper in a little more detail and give you all an insight into my research.

What exactly is Elastic Facial Caricature Warping?

The Subject2. Beautification1. Caricaturisation

3. Deviation

He’s Beautiful!Hee! Hee!Ha! Ha!Uh oh…We’ve gone

too far!

The History of the Caricature

• Caricatures are portraits that exaggerate or distort the essence of a person to create an easily identifiable, but humorous, visual likeness.

• Some of the earliest caricatures are found in the works of Leonardo da Vinci, who actively sought people with deformities to use as models!

• Caricatures gained further popularity in the early 19th century, when satirical drawings of politicians and local celebrities would be printed in newspapers, however they were often not warmly received.

• After WW1 the appeal of caricatures rose dramatically and they became a very common sight in most magazines and newspapers due to large demand from the public.

Early Caricature of Charles Darwin (1880)

Modern Caricature of Arnold Schwarzenegger


Caricaturisation


• Caricaturisation is an Art– Caricatures are a form of visual art, in which subjects are portrayed

with exaggerated features that emphasise their individual differences from everyone else.

• [L. Redman, How to Draw Caricatures, Contemporary Books, 1984]

– The aim of a caricature is to provide an amusing source of entertainment and humour, especially in western society.

• Caricaturisation is a Science– A caricature is typically drawn by emphasising all of the features

that make that person different from a completely symmetrical reference face, perceived by the artist to be the ‘norm’.

– Craniofacial Anthropometry can be used to provide important facial measurements that should be considered during the creation of the caricature. An example of some of these measurements are shown on our reference image on the right.

• Caricaturisation is Computer Graphics– Our aim therefore is to unite the disciplines of art and science by

introducing a novel and entertaining, physics based approach to the creation of caricatures using computer graphics. Our Reference

Face with Feature Points

A Caricature

Beautification


• ‘Beautification’ is the process of physically making something appear more beautiful by altering its physical structure in some way.

• Facial beauty is characterised by the following factors:– SYMMETRY – PROPORTION OF FEATURES– FEATURE PLACEMENT– PROFILE OUTLINE– BABYFACEDNESS

• According to some research, the more ‘perfect’ a person’s face is, the healthier they should be.

• Like Caricaturisation, Beautification is also related to average face construction, since a perfectly average face is considered to be more beautiful than a standard face such as mine or yours, because all the factors I just metioned are obeyed.

Dolichocephalic

Brachycephalic

Straight

Some Symmetrical FacesSubject

Symmetry of left side of face

Symmetry of right side of face

The System Pipeline


1. Input 3. Calculation2. User Interaction 4. Result

Scheme AScheme BScheme CScheme D

System computes

displacements and

applies chosen model

to image

Source Image

User chooses model

Feature Specification

Feature Specification• Feature Specification:

– How do we calculate the necessary displacements?• The distance between each pair of corresponding feature points on

the reference and subject’s face encodes a measurement used in the transformation.

• These measurements and then used in our physical model to create the caricature.

– More formally:• Let Iin be an input image of a subject to be caricaturised; Iref be a

reference image, representing the ‘norm’; and Iout be the output image of the caricature to be generated. Given a feature point p on image Iin and its corresponding feature point r on Iref, we would like to determine q on Iout as the resulting exaggerated feature point:


The Force - Motion Model

• This is the first model that was developed, and it works by imagining that each feature point on the subject is a particle in motion.

• Mathematically it is based on Newton’s Laws of Motion, given as:

• Two different schemes were developed in this model:– Scheme A — Controlling by Time:

• Each particle moves from its origin over a user-defined period of time.

– Scheme B — Controlling by Force & Mass:

• As an extension to A, each particle can be assigned a weight and a global or local force can also be applied.


20

20 22

1)( t

m

Ftvattvtd

The Pseudo Stress – Strain Model

• It is natural to associate caricaturisation with the process of deformation by stretching or compressing different parts of a face. This directly leads to the use of metaphors related to material properties and mechanics.

• Our pseudo stress-strain model can be given as:

• Users can apply different ‘virtual’ material values to the facial features in order to produce different caricatures.

• We have developed two separate schemes in this model:– Scheme C: Non-Uniform Original Length– Scheme D: Uniform Original Length

)/(/ leAF


Virtual Material Properties

• Instead of explicitly specifying displacements, users can assign ‘virtual’ physical and material properties to the face in an intuitive manner.

• Not only does this provide users with intuitive metaphors for specifying a desired caricaturisation, but it also introduces a novel, and more entertaining aspect to the caricature generation process.

Virtual Material

Hookean coefficient

Non-Hookean

coefficient

Maximum Strength

Rubber 0.01 0.1 7Polystyrene 2.8 0.9 35Wood 12 0.95 75Brick 18 1.2 39Glass 65 2 500Gold 83 0.92 120Steel 205 0.99 1000Diamond 950 1 12605

Some Material Properties used by the System


An Example –Scheme D: Uniform Original Length

• An assumption is made that the line segment between reference and subject points has been stretched from its original length (u). This value is then used with any two material value properties to complete the warp.

uFud 1

2 )/(

Beautifying Caricaturising

Rubber

Polystyrene

Silicone

Wood

Concrete


Future Work + Possible Applications

• There are many areas that I will be exploring in order to extend this work further for my PhD.

• Currently however the main theme I am working on is extending the system so that it produces a 3D result from 2D input images using depth maps.

• Possible Future Applications:– ‘Edutainment’ Software for school children.– Plastic Surgery prediction aid.– General entertainment/fun software for use by

everyday people in their own homes.

3D caricature of Albert Einstein

Some Results…


THANK YOU!

Any Questions?


elastic facial caricature warping lyndsey clarke cslyndsey ~ phd student ~ ~ university of wales...

Documents

caricature caricatures

caricature slide

cslyndsey slide

caricaturisation http

cslyndsey caricaturisation

art caricatures

creation of caricatures

beautification http