1. Hyper-Realism in an Animated
World: Simulating the Human Body
Can You Spot The Differences?
Sunday, March 23, 14
2. Hyper-Realism in an Animated
World: Simulating the Human Body
Can You Spot The Differences?
Grand Theft Auto III
Heavy usage of playback
animation.
Repetitive scenes with animated
characters.
Clumsy Ninja
Dynamic simulation using physics-
based game engine.
Unique scenes with fully interactive
characters.
The Fundamental Differences
Sunday, March 23, 14
3. The Fundamental Differences
Grand Theft Auto III
Heavy usage of playback
animation.
Repetitive scenes with animated
characters.
Clumsy Ninja
Dynamic simulation using physics-
based game engine.
Unique scenes with fully interactive
characters.
Sunday, March 23, 14
4. Objectives:
A brief introduction into how physics have been
incorporated into games over time.
How the physics game engine takes the human body
and transforms it into a virtual character.
How physical constraints are used to achieve a
realistic looking character and virtual world.
An understanding of the different applications of this
technology.
An introduction and/or increased awareness of a
rapidly-growing industry that fuses science with
technology.
Sunday, March 23, 14
5. A Brief Overview of Progress:
“Evolution” of Physics in Gaming
pre-1980’s: Some of the first video
games incorporate basic principles
of physics (i.e.. projectile motion),
astrophysics and mathematical
modeling.
1980-1990: Nintendo unveils its home
entertainment system, with games like
Donkey Kong and Super Mario Bros.
showcasing more concepts of physics:
friction, momentum and gravity.
Sunday, March 23, 14
6. 2000 and beyond: Increased commercialization
of rag-doll physics for more realistic death
scenes: life-like animations simulated in real
time. Physics game engines lead to increased
implementation of physics in games.
A Brief Overview of Progress:
“Evolution” of Physics in Gaming
1990-2000: Computers, with better
processing power, see improved graphics
and more opportunities to use physics:
more realistic collision and damage scenes.
Sunday, March 23, 14
8. The Player: Skeleton
A virtual skeleton is modeled as a series basic geometric
shapes: cylinders, rectangles, and spheres.
A virtual skeleton is articulated with joints similar in
function to human joints.
JointsSkeleton
Sunday, March 23, 14
9. The Player: Joints
Spherical joints
articulate similarly
to ball-and-socket
joints.
Revolute joints
articulate similarly
to hinge joints.
D6 joints are custom joints, which can be
programmed to rotate freely in any axis.
Sunday, March 23, 14
10. Torque and Joints:
Hard and Soft Limits
Soft limits represent a natural range of motion.
Hard limits indicate the maximum range of motion at a particular joint.
Soft and hard limits imposed on joints help differentiate realistic from
non-realistic characters.
Sunday, March 23, 14
11. Muscular System
Additional software layered on top of the
physics game engine simulates the
muscular system.
Each joint has a “muscle” associated with
it, called a motor.
The motor functions similarly to muscle,
and is responsible for movement of the
joint.
Animations of muscles are for visual
purposes only.
Sunday, March 23, 14
12. Muscular Systemethod on separate parts of the visual mesh. Middle and right:
pe and skirt interacting with each other and the body. Model
(c)
skeleton
(a) (b)
(d)
Figure 3: 2D cross section through a simulation of a shirt
on a character. The inputs are a visual mesh for the skin (a)
and a visual mesh for the shirt (b) with skinning information.
Oriented particles are placed on the visual meshes. The yel-
low particles are simulated and the red particles animated,
following the skeleton. Animated particles are used to at-
tach the simulation mesh (c) or as collision primitives (all
others). The vertices of the visual meshes are marked to be
skinned to either the skeleton (black) or the particles (green)
with smooth transitions as between vertices (c) and (d).
of the skeleton and the superscript vb indicates vertex-bone
skinning. Vertices are skinned to the skeleton via
xi = Â
j
wvb
i,j Brvb
i,j
(¯xi), (2)
The skin is modeled as a mesh of particles
that lie on top of the player.
The particles move according to known
kinematic equations, with damping.
Shapes that lie underneath the skin may
be programmed to stretch or compress to
achieve the visual effect of a flexed
muscle.
a) Virtual skin mesh.
b) Virtual clothing mesh.
c) Point of contact where clothing and
skin animate in conjunction.
d) Point where clothing is simulated as
free-flowing.
Sunday, March 23, 14
13. Genetic Algorithms
Self-learning algorithm that
mimics the theory of
evolution.
Techniques incorporated
include: inheritance, mutation,
recombination and selection.
This process over many
generations until an individual
arises that possesses all
desired traits.
Sunday, March 23, 14
14. Simulation of the
Nervous System
Generation 1: Not able to walk at
all.
Generation 10: Some walking, but
unbalanced and hesitant.
Generation 20: Walking in a
straight line.
Individuals in the genetic
algorithm are neural
networks based on the
human nervous system.
Traits are represented by
strings of code.
Sunday, March 23, 14
15. Setting the Scene: Physics
of the Environment
MomentumFrictionGravity
Sunday, March 23, 14
16. A Trend Towards Realism
and Interactivity
Increased computational power
allows developers and
programmers to things not
possible to do before: visually
and physically.
A direct correlation exists
between the believability of a
virtual character and
enjoyment of that character.
Sunday, March 23, 14
17. Applications of Simulated
Human Bodies
Surgeons can use this technology to simulate the gait
of an individual with Cerebral Palsy. In this way, they
can visualize the effect a correction would have
before performing surgery.
Virtual stuntmen.
Realistic characters in Hollywood productions.
Sunday, March 23, 14
18. Suggestions for Improvements
Muscles can be programmed
to fatigue after strenuous
activity.
Animations to display injuries
with real-time recovery.
Programmable AI behaviors
to show a characters mood
by way of facial expressions
and body language.
Sunday, March 23, 14
