Personajes digitalesAndrés Adolfo Navarro Newball

Personajes digitalesArticulation and animation of

digital creatures is informed by understanding of human and animal anatomy

Digital creatures can be realistic, fanciful, animal-based, or any combination thereof

Personajes digitalesTodas tienen anatomíaSus anatomías, realistas o no, se

basan en estructuras anatómicas de organismos existentes.

Deben funcionar de acuerdo a las leyes físicas de su propio entorno

Personajes digitalesPersonajes realistas se benefician

de los organismos que buscan imitar

Personajes nuevos. Pueden ser diseccionados en componentes basadas en organismos reales

Personajes digitalesLa clave es la estructura anatómica

básica Analogía evolutiva entre las

estructuras que dan movimiento

Young Sherlock Holmes, Caballero del vitral, 1985http://www.youtube.com/watch?v=CT-qV41ovv4

http://www.youtube.com/watch?v=v_FfHA5whXc

FormaRestringida por el ambiente

◦ Terrestre / acuático◦ Dieta◦ Velocidad de movimiento

Piel◦ Skin of a biological creature cannot hold

its form without the underlying anatomy◦ The skin of a digital creature exists

without need for support from underlying structures.

Forma The form of a biological creature is determined by the

expression of those underlying structures through the skin.

It is important to understand how the form of the digital creature could conceivably be built up from the inside

The responsibility for identifying anatomical elements falls primarily to the artists tasked with creating the animation rigging and deformation systems for the creatures. Saphira, Eragon

http://www.youtube.com/watch?v=bpkwhr5P0l4

Forma Bulge: fat, organ, muscle, cartilage, or

bone◦ If bone: connection point for articulations?◦ If muscle: relaxed or contracted?

Ridges:◦ Convex curvature of bulges

Bulges and ridges communicate the existence of anatomical elements under the skin.

Cavities and creases the absence of support for the skin. Areas of great articulation

Forma

Preferible modelar en una pose neutral

Articulación Rigging:

Construir el sistema musculo-esqueletal de un personaje

Tomar un modelo inanimado y transformarlo en un personaje que el animador puede manipular cuadro a cuadro para crear movimiento

Ensamble de una estructura de soporte. Soporte requerido mas para articulación que estructural

Determina numero y posición de puntos de articulación

Luego, se relacionan los puntos de articulación a la piel

Articulación Músculos orientan movimiento

del sistema esqueletal… Pero los esqueletos limitan los

rangos de movimientoEj: The Atlas-Axis Joint of the

Upper Neck Head◦Separación del movimiento “si” y

“no”

Articulación En estos “huesos” digitales el

movimiento es realizado con translaciones y rotaciones.

Pueden ser movidos rotados, escalados en el espacio

Pueden conectarseBásicamente constan de un pivote y

una longitud. Conectados al end point de su padre.

Desconectado de otros objetos, no sirve de mucho

Articulación

Jar Jar Bink’shttp://www.youtube.com/watch?v=5C9JX6VRjn0

Articulación Biological accuracy to the number of bones

is necessary only if photorealistic representation of an actual skeleton is required

The effect of individual bones in a biological system on the articulation and deformations of skin is mitigated by the action of other parts of the system

Articulación Accuracy in the location of pivot points, the

way the bones behave relative to one another in the deformation of surfaces is more important than the number of bones for digital creatures

There are various techniques that can be employed digitally to replicate the volume preserving function of the rib cage and digestive organs, but often the more efficient solution is to simply deviate from the biological placement of the spine joints

Sistema de controlManera como la intención se

convierte en acción Key frame Captura de movimiento Procedimental

ConexiónMantiene las partes del sistema

juntas.◦ Directa: jerarquía padre – hijo

El movimiento del padre orienta la posición del hijo Estructuras anatómicas mas complejas requieren

mayor estudio

◦ No jerárquica: Permite orientar el movimiento de un hueso gracias

a agentes externos Reduce problemas relacionados con cálculos

◦ Variable: Relación matemática entre objetos Crea comportamientos dinámicos

Creaturas sin huesoAltamente deformablesLos puntos de articulación se

mueven constantemente uno respecto al otro

Se pone una columna y conexiones variables

MovimientoPueden responder a las

siguientes leyes:◦Físicas◦Estructura / morfología◦Funcionalidad de la estructura◦EJ:

http://www.youtube.com/watch?v=N64KOQkbyiI http://www.youtube.com/watch?v=mYHK3wL11

eI&feature=related

Medio en que se mueve el organismo

Movimiento

Movimiento Visible motion that appears internally motivated

or the result of internally motivated action. However, the initiation of the action for a digital creature is external, puppeted

Barriers to motion can also be created but they are computationally expensive if applied as collision detections. More often limitations are programmed into the rig

Driving points in digital creatures are locations where several appendages join together. Controlling a driving point moves the origin points of appendages as a group

Movimiento Physically driven actions for digital creatures

typically exist as layers of motion applied on top of the primary action

Forward kinematic systems describe each joint’s position as solely derivative of it’s parent’s action. In a forward kinematic system the rotation of a parent joint drives the position of the child

An inverse kinematic system describes each joint’s position relative to the action of the last joint in the chain. In inverse kinematic systems the joints between the root and the end joint must solve their positions using the first and last joints as guides

MovimientoDynamic posing differs significantly from IK

and FK techniques. It consists of a non-hierarchical arrangement of articulation points and a dynamic solver that determines how those points relate to one another

The typical role for digital muscles is to act as secondary deformers of the skin during motion.

Hollow man, 2000http://www.youtube.com/watch?v=BMHsrGA061o

MovimientoDeformación: creation of a digital

analog to the effect of bones and muscles moving skin◦Enveloping◦Skinning

Caso 1, el gato con botasEl mejor papel de Antonio

Banderas a la fechahttp://www.youtube.com/watch?v

=7LbumSMoQK8

El gato con botas

El gato con botas

Character setup includes: joint articulation and limb motion, facial animation (simulated muscles, jaw

movement, skin stretching), body deformations to represent muscle

and skin behavior, hair and fur motion, the hierarchy of body part relationships, special character props such as Puss’

animated hat.

El gato con botasDevelopment

◦Involves designing the technical solutions needed to help realize the Director’s creative vision for the project

Design and implementation of the rigging systems

Ongoing Support of the animation rigs for Character Animators once Production begins.

El gato con botasPuss-In-Boots: One

Complicated Cat

El gato con botasUltimately, the rig of Puss-In-

Boots involved designing, building, testing, refining, and supporting a complex motion system. For Puss-In-Boots, the motion system was extremely complex and involved a large number of individual components far beyond anything that was constructed for Shrek

El gato con botas

El gato con botas If, for example, a character needs to be able

to achieve certain actions, then a rig must be constructed that enables the character with those capabilities. In this case, what started out as a cat eventually required the ability to also stand up and walk on its two hind legs just like a human.

Part of the work involved setting up multiple sets of joints—joints that worked differently depending on the situation he was in (whether he was in cat mode or human mode).

El gato con botasPivote en modo gato

Balance:dedos largos pero no tanto

El gato con botas The height of the boots on the inside-back

of Puss’ legs, maintaining the original height on the outside-front. This way, the boots appear to ride high but do not require lots of necessary collision detection

The first model of Puss-In-Boots started out as a real cat (a tabby). But in order to achieve recognizable human facial expressions, his face was slowly pushed towards being more human.

El gato con botas

El gato con botasAlthough the feather strands were

added by the FX department, the spine of the feather became fully animatable as well

To accompany Puss’ boots, Puss also dons a wide, brown leather belt. The belt can be animated so it slides over his body interacting in a believable way with the fur

El gato con botasThe functions of the Character TD department

include:◦ Ensure character designs are functional and

aesthetically match the Director’s vision,◦ Define character setup standards,◦ Develop character setup technology,◦ Implement and integrate the character setup system

(motion system, facial animation, body deformations, tight clothing/wrinkles, whiskers/hair setup plus dynamics, character props setup plus dynamics

◦ Set up characters for animation, and◦ Support characters throughout all phases of

production for the Character Animation and Lighting departments

Caso 2, Los lobos alfa

Los lobos alfaThe system allows the user to have

high-level control over the actions of a character, while the emotional state of the character is autonomously maintained by the computer

Each pup forms a social relationship with the other; the next time they meet, their remembered relationships will affect the way in which they interact

Los lobos alfaEach wolf maintains an emotional state

that is affected by its interactions with the world. A wolf is able to perceive the identity of its pack mates, recognizing them as distinct individuals. It forms an emotional memory of each individual after its first interaction with it

It was necessary to choose a computational representation that captures the necessary range of emotional phenomena

Los lobos alfa

SkinningLa piel se debe mover y deformar junto

con el esqueletoBrinda correspondencia entre piel y

esqueleto a través de una serie de pesosDefine el movimiento de la piel como

una función del esqueleto Asociar una malla al esqueletoAlgunos métodos:

Skeletal Subspace Deformation: poco flexible Animation Space: el mejor Multi-Weight Enveloping: overfitting

Skinningv: posición de un vértice : posición de reposo de v 1 ... b: huesosTi = matriz de transformación del

i – esimo hueso = Ti en reposo

v̂

iT̂

SkinningConvertir la posición del i - esimo

vértice en reposo de coordenadas del modelo a coordenadas del hueso

SkinningConvertir el vértice en

coordenadas de hueso a coordenadas del modelo

Skeletal Subspace DeformationOtros nombres:

Linear Blend Skinning, Enveloping and Vertex Blending

Determines the new position of a vertex by linearly combining the results of the vertex transformed rigidly with each bone

Skeletal Subspace DeformationA scalar weight, wi, is given to

each influencing bone and the weighted sum gives the vertex’s position

Animation spaceProvides greater flexibility than SSD

by changing the single rest pose position of each vertex

Allows each component of the vertex’s position to be influenced independently by each bone

Multi-Weight Enveloping

These additional weights allow each component of v to be influenced, independently of one another, in each component of a bone’s movement.

Bibliografía The Morphology of Digital Creatures Tim McLaughlin, Stuart S. Sumida

Ph.D. Art-Directed Technology: Anatomy of a Shrek2 Sequence

SIGGRAPH 2004 Course. Rachel Falk, Denise Minter, Conrad Vernon, Guillaume Aretos, Lucia Modesto, Arnauld Lamorlette, Nick Walker, Tim Cheung, Janet Rentel-Lavin, Harry Max

Leashing the AlphaWolves: Mixing User Direction with Autonomous Emotion in a Pack of Semi-Autonomous Virtual Characters. Bill Tomlinson, Marc Downie, Matt Berlin, Jesse Gray, Derek Lyons, Jennie Cochran, and Bruce Blumberg Synthetic Characters Group, The Media Lab, MIT

A Comparison of Linear Skinning Techniques for Character Animation. David Jacka, Ashley Reid, Bruce Merry, James Gain, University of Cape Town

Autonomous Animation and Control of Four-Legged Animals. Evangelos Kokkevis, Dimitri Metaxas and Norman I. Badler

The 3D Skeleton Pruning for Removing Undesired Joints. Porawat VISUTSAK, Korakot PRACHUMRAK

Skinning Mesh Animations. Doug L. James Christopher D. Twigg