Realistic Speech Animation on Synthetic Faces

Barış Uz, Uğur Güdükbay, Bülent Özgüç / Bilkent University

Computer Animation’98 / 1

Realistic Speech Animation on Synthetic Faces

Barış Uz, Uğur Güdükbay, Bülent Özgüç

Bilkent UniversityDept. of Computer Eng. and Information Science

Bilkent 06533 Ankara Turkey



Outline Previous Work

– Facial Animation– Speech Animation

Face Model Facial Muscles

– Linear Muscles– Orbicularis Oris

Tongue Model Speech Animation Synchronizing Speech with Expressions Future Work



Facial AnimationKeyframing [Parke’72]: Each keyframe must be

completely specified. Tedious for 3D facial animation.

Parametric [Parke’82]: A set of parameters for the face is defined. – Expression parameters: apply to different parts; jaw

rotation angle, width of the mouth, eyelid opening, eyebrow position and shape, etc.

– Conformation parameters: apply globally to the whole face; aspect ratio of the face, skin color, etc. Since each parameter effects a disjoint set of vertices, cannot easily blend facial expressions.



Facial Animation (cont.)

Structure based [Platt’85]: the face is divided into regions based on anatomy of the face.

Physically-based [Terzopoulos and Waters’90]: the face is modeled in a layered fashion; an anatomically-based muscle model is incorporated with a physically based layered tissue model.



Speech AnimationGenerating Speaking Face Models: model mouth and

lip postures and interpolate them– Parametric approach [Parke75]– Image-based approach [Watson96]: morphing

algorithm to interpolate phoneme images– [Waters and Frisbie’95] Coordinated 2D muscle

model to model muscle interactions– [Basu’97] 3D model of human lips and a framework

for training it from real data. Mainly for reconstruction of lip shapes from real data but can be used for lip shape synthesis



Synchronizing Speech with Animation Non-automated techniques: changing the audio

requires the whole synchronization process to be repeated.– Parke’75– Pearce et al. 86

Automatic techniques: An audio server is queried for each phoneme so that a mouth shape is computed synchronously.– DecFace [Waters and Levergood’93]



Generation of Facial Expressions

Layered abstractions [Kalra et al.’91] : Higher layers allow abstract manipulations; speech is synchronized with eye motion and emotions using a synchronization mechanism provided by a high-level language

Animated conversation [Cassell et al.’94]: animated conversation between multiple human-like agents with synchronized speech , intonation, facial expressions and hand gestures.



Face Model Face model consists of 888 triangles (1700 including

eyes, teeth and tongue) Face is divided into three regions

– Upper (610 triangles), lower (240 triangles) and intermediate

Changes to the original model– Repeated the mouth vertices to open and close the mouth– Added some polygons to close the nose – Added eyes and teeth to the model– Added a simple tongue



Regions of Face

Upper region

Intermediate region

Lower region



Motion (Muscle) and Vertex Relationships

Vertex TagMotion orMuscle Tag

UPPER LOWER BOTH NONE JAWROT

UPPER + - + - -

LOWER - + + - -

BOTH + + + - -

JAWROT - + + - +



Facial Muscle Vectors



Major Facial Muscles Orbicularis Oris : most significant role in composing

the shape of the mouth; a sphincter muscle. Mentalis, buccinator, depressor anguli oris major,

depressor labii inferioris : lower lip and lower face is controlled by these muscles

Zygomatic minor, levator labii superioris alaeque nasii : Upper face muscles; rarely used for speech; important for expressions

Zygomatic major, risorius : located around cheeks; important for expressions



Modeling of Muscles

Types of muscles– Linear: e.g., zygomatic

major (smiling)

– Sphincter: e.g., orbicularis oris (mouth opener)

– Sheet: e.g., orbicularis oculi major (eyelid opener)

Muscle parameters– Influence zone: between

35 and 65 degrees– Influence start: Muscle’s

influence starts at this tension

– Influence end: After this tension, skin resists deformation

– Contraction value: muscle tension



Modeling of Muscles (cont.) P: original position P’: new position Rs and Rf influence start

and finish radii maximum zone of

influence D: distance of P from

muscle head : angular displacement

from muscle vector



Muscle deformation [Waters’87]If P is in V1P3P4

P P karPV

PV1

1

r

D

RD R

R R

s

s

f s

cos(( ) )

cos(( ) )

1

2

2

where

k is a muscle spring constant,

a=cos(a),

if P in (V1 P3 P4)

if P in (P1 P2 P3 P4)



Orbicularis Oris

Modeled as 4 linear muscles Horizontal ones have 40 degrees of influence; vertical ones have

140 degrees of influence Very practical to implement A pseudo-muscle is added to simulate protrusion and purse

effects for lower lip (f-tuck); necessary to say letters “f” and “v”

Real placement ofOrbicularis Oris

Our abstraction forOrbicularis Oris

Muscle for f-tuck



The Tongue Model Tongue is composed of 4 sections of 20 polygons

+ 12 polygons to close the tip Tongue is reconstructed for each change

in the parameters Each section has the following parameters

– height: height of the section floor from the tonguebase

– width: total width of the section

– length: length of the section

– thickness: thickness of the tongue

– midline: height of the middle line of the tongue



The Tongue Model (cont.)

Top view Frontal view



The Tongue Model (cont.) For example, to say the letter “l”,

– there is no change in section 1 (the farthest section)

– In section 2, the width will be reduced to 1/2 of the relaxed width

– In section 3, the width will be reduced to 1/3 of the relaxed width and the height will be increased properly

– In section 4, the width will be reduced to 1/4 of the relaxed width and the height of the tongue will be equal to the bottom of upper teeth. The midline will be equal to the thickness of the tongue in section 4.



Speech Animation Keyframing based on muscle parameters around the

mouth and jaw rotation. Each keyframe is a mouth shape dictated by the

current expression setting and the current letter. Cosine interpolation is used to generate inbetweens The database for mouth shapes contain

– the letter: the key field

– the muscle contraction values: determining which muscles are active while pronouncing this letter

– jaw rotation angle: necessary for some letters



Speech Animation System

Input Text Parser

Expression

LetterFacial

AnimationSystem

Database



Synchronizing Speech with ExpressionsGuessing from text

– Punctuation marks

– Keywords

– From the meanings of words

Ambiguous! different meanings of the same word, punctuation marks and keywords

By inserting tags into text Insert tags into text to specify

expressions and their degrees explicitly

\b{expression level}: starts an expression of degree level. If the expression is set before, it is used to increase the degree of the expression.

\e{expression level}: ends or decreases the degree of an expression by level. If level is -1, the expression is removed from the face.



Speech Animation AlgorithmWhile not all of the text is processed 1. Read a character 2. If a tag is beginning /* "\" is read */ 2.1 Read tag /* name and degree of expression */ 3. If degree is -1 3.1 Remove expression from the face else 3.2 Set face according to expression with specified degree 4. If a valid character /* a letter or a punctuation mark */ 4.1 If this is the first character to say 4.1.1 Set face using current expression and letter settings 4.1.2 Display face else 4.2 for each in-between 4.2.1 Calculate vertex coords using cosine interpolation 4.2.2 Display face 4.3 Store vertex coords for future reference



Future Work

Better mouth postures Implementation of coarticulation Synchronization of synthetic speech with

facial animation (Turkish speech synthesizer is syllable-based; we should form a database of mouth postures for 2000 Turkish syllables and group them with respect to similar mouth postures)

Realistic Speech Animation on Synthetic Faces

Documents

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