3D Virtual Viewer with
integrated Newton Physics
Engine
PROJECT REPORT
ALAIN VINIOT DE LARA
Professor C. Sun
CS 491B Spring 2007
1. Abstract
O n e o f t h e m o s t e x c i t i n g f i e l d i n c o m p u t e r s c i e n c e i s V i r t u a l R e a l i t y, i t
provide the user with visual experience, made from virtual environment
simulated with the computer. There has been increasing interest in the
potential social impact of new technologies, specially virtual reality
w h i c h w i l l l e a d t o s o m e c h a n g e s i n h u m a n l i f e a n d a c t i v i t y.
Modern artist have been interested in this technology to create
imaginative worlds in virtual space. The immersive capability of VR is
starting to change the way people use the computer and manipulate digital
information.
2 . Introduction
Virtual Reality and 3D Video Games are exciting fields in computer
science, commercial 3D video game products are the most profitable,
m a n y p e o p l e e n j o y p l a yi n g v i d e o g a m e s . T h e f i r s t p e r s o n s h o o t e r e v e r
produced, Wolfenstein3D was an instant hit and its progeny DOOM is
recognized as the notorious pioneer for its use of immersive 3D graphics.
B u t g e t t i n g t o m a k e a 3 D v i d e o g a m e i s a n o t h e r s t o r y, t h e r e q u i r e m e n t s t o
produce these products are very demanding, the computer scientist that
work in video game production are considered elites in computer science.
The engineer that wants pursue a career in this field must master many
s u b j e c t s s u c h a s m a t h e m a t i c s , p h ys i c s , c o m p u t e r g r a p h i c s . I t r e q u i r e s
talent, ambition, experience, the skill level are often so high t hat only
few talented people can get involved.
For early video games, a single programmer could handle almost all the
tasks needed to develop a game. However modern video game production
involves a wide variety of skills and support staff. The productio n team
has at least one lead designer, several programmers, many artists, sound
engineers, level designers and testers. Imaginative and creative minds are
required for this type of job. Every elements is critical to the success of
the product, the work of the programmer is the most important.
Developing computer game is a team effort, and each member is
expected to have high skills in their field, competion is intense, so people
have to keep up with the latest techniques and trends.
Most modern 3D video games all use sophisticated 3D engines such as
OpenGL and DirectX to render the virtual environment, more advanced
ones are using physics engines to simulate Newtonian physics, such as
m a s s , v e l o c i t y, c o n s e r v a t i o n o f m o m e n t u m , f r i c t i o n a n d e l a s t i c i t y. T h e r e
a r e t w o t yp e s o f P h ys i c s e n g i n e , h i g h p r e c i s i o n a n d r e a l - t i m e , t h e l a s t
o n e i s t a k i n g t h e f a s t a p p r o a c h , b y s i m p l i f yi n g c a l c u l a t i o n a n d l o w e r i n g
t h e p r e c i s i o n t o i m p r o v e t h e r a t e o f g a m e p l a y.
M a n y t yp e s o f r u n t i m e p h ys i c s e n g i n e e x i s t , a r e d i f f e r e n t i n q u a l i t y
a n d p e r f o r m a n c e , I c h o o s e t h e N e w t o n P h ys i c s e n g i n e , b e c a u s e i t i s f r e e
to use, one of the most accurate, can handle higher to mass ratios and
simulation is very robust. There are some instability in the engine, an
experienced programmer must know to fine tune the engine to avoid being
in the "unstable zone".
D u e t o p h ys i c a l i n t e r a c t i o n b e t w e e n p h ys i c s o b j e c t a n d t h e
e n v i r o n m e n t , I c a n n o t u s e a p h ys i c s o b j e c t t o s i m u l a t e t h e p l a ye r c o l l i s i o n
detection, because it will cause jittering for the view, so I implemented
m y o w n t e c h n i q u e f o r c o l l i s i o n d e t e c t i o n . T h e r e s t o f t h e p h ys i c a l
interactions are provided by the Newton engine.
The general idea for this project is improve the speed of production, I
u s e m y o w n 3 D e d i t o r t h a t c a n e d i t p o l yg o n s , a t t a c h t e x t u r e s , i n s e r t
p h ys i c s o b j e c t s t h a t c a n b e s a v e d a n d l o a d e d l a t e r . T h i s e d i t o r c a n l o a d
3D mesh objects from some other file formats, so that, if the editor
cannot edit some complicated shapes, it can rely on another program to do
s o . A n u p g r a d e t o t h e 3 D e d i t o r w a s a p p l i e d t o s a v e P h ys i c s O b j e c t s , t h e
viewer program is reading from a file and render the result. The editor is
much more complicated than the project itself, if we upgrade the editor
further, we will need less programming, w e will only need to be
proficient in using the editor to produce video games, it’s equivalent of
u s i n g a w e b p a g e e d i t o r i n s t e a d o f t yp i n g i n H T M L d i r e c t l y. T h i s e d i t o r i s
still a work in progress.
3 . Techno log ica l Ba ckground
3 .1 B o r l a n d D e l p h i
Borland Delphi is one of the first development tool to be known as
RAD (Rapid Application Development), the interface is similar to Visual
Basic with better performance, its predecessor was Turbo Pascal which
was the fastest compiler in the pre -windows era. Delphi most popular use
is the development of desktop and enterprise database application for
Windows.
I t i s b a s e d o n a w e l l d e s i g n e d l a n g u a g e , h i g h l e v e l a n d s t r o n g l y t yp e d
with low level escapes for experts. It can compile to a single execu table,
s i m p l i f yi n g d i s t r i b u t i o n a n d r e d u c i n g D L L v e r s i o n i n g i s s u e s . M a n y v i s u a l
components library and third party components are available with source
code, it can optimize compiling and use assembler code.
Multiple platform native code from the same source code is provided
s u c h a s C r o s s K yl i x .
3 .2 N e w t o n G a me Dy n a mi c s
N e w t o n G a m e D y n a m i c s i s a f r e e , b u t c l o s e d s o u r c e p h ys i c s e n g i n e f o r
realistically simulating rigid bodies in games and other real -time
a p p l i c a t i o n s . I n c o n t r a s t t o m o s t o t h e r r e a l - t i m e p h ys i c s e n g i n e s i t g o e s
for accuracy over speed. Its solver is deterministic and not based on
traditional LCP or iterative methods. The advantages are that it can
handle higher mass ratios (up to 400:1) and the simulation
is very robust and easy to tune. The disadvantage is that it is a bit
s l o w e r t h a n p h ys i c s e n g i n e s w i t h a n i t e r a t i v e s o l v e r .
Newton Game Dynamics gets used in a lot of non -commercial,
commercial and academic projects. It is a popular choice in the Irr licht
and OGRE communities.
T h e N e w t o n G a m e D yn a m i c s S D K L i c e n s e a l l o w s d e v e l o p e r s t o f r e e l y
incorporate the engine into personal projects or commercial products so
long as credit is given and the engine is distributed solely as part of a
c o m p i l e d s o f t w a r e p r o g r a m t h a t i s i t s e l f n o t a p h ys i c s e n g i n e . N e w t o n
G a m e D yn a m i c s i s a c t i v e l y d e v e l o p e d b y J u l i o J e r e z w h o f r e q u e n t s t h e
forums on the official website.
Currently a new version which will take advantage of multi -core cpus
and gpus is in the works.
Features:
- easy to use C-API
- available for windows, osx, linux
- plethora of convex collision shapes
- compound collision shapes
- continuous collision mode
- hinge, ball, slider, corkscrew,... and custom joints
- powerful custom constraint/joint API
- special vehicle container
- special ragdoll container
- also usable as a stand -alone collision detection library
3 .3 S e l f Ma d e 3 D E d i t o r
The 3D editor was coded entirely by myself, although I use some extra
library such as for loading textures, OpenGL/DirectX headers. The editor
is still a work in progress. It is easy to create almost any shapes , we can
p o s i t i o n , r o t a t e p o l y g o n s b y g r o u p s o r i n d i v i d u a l l y. T h e s a m e c a n b e s a i d
about cameras, lights, translator, rotators.
The features of the 3D editor are the described below:
- p o l yg o n / v e r t e x e d i t i n g ( t r a n s l a t i o n a n d r o t a t i o n )
-Texturing by plane projection, cylindrical and spherical.
-Skeletal animation with polygons
- S u b d i v i s i o n w i t h B u t t e r f l y, L o o p a n d C a t m u l l - C l a r k m e t h o d .
-Loading 3DS file
-Rotating/Translating with scrollbar or mouse trackball
-Transparent polygon editing/ degree of transparency
- M a n u a l s h a d i n g o f v e r t e x a n d p o l yg o n s
-Mirroring, Point Extrusion.
-2D to 3D tools: Pivot, Path, 3D terrain editing,Extrude Tool.
- C o l o r i n g v e r t e x o r p o l yg o n s
-Filtered selection
-Wire-frame or Gouraud shading view
-Triangulation
-Bicubic Spline and Bezier 3D Patch
-Sizeable window view and focal lens adjustment.
-Calculate Shadow and generate lightmaps files.
-Pre-calculate before saving collision vectors and scalars.
- P h ys i c s o b j e c t e d i t i n g , w e c a n s i z e t h e m i n t h e X , Y , Z d i r e c t i o n .
4 . System Ov erview
T h e 3 D v i e w e r i s c a p a b l e o f g e n e r a t i n g 3 D P h ys i c s o b j e c t s o r l o a d
from file, it depends on the 3D editor to produce the meshes. It can
process collision detection by switching a menu item, the mass o f the 3D
p h ys i c s o b j e c t s a r e h a r d c o d e d .
I choose to give a specified mass so that the engine behave with
s t a b i l i t y. R e n d e r i n g i s d o n e b y u s i n g O p e n G L , i t r e n d e r o p a q u e n o n l i g h t e d p o l yg o n a n d t r a n s p a r e n c y i s n o t s u p p o r t e d e v e n t h o u g h t h e e d i t o r
a l l o w t o s p e c i f y l i g h t i n g a n d t r a n s p a r e n c y, d u e t o t i m e c o n s t r a i n t n o t a l l
wanted features were finished.
5 . Desig n a nd Implementa tion.
5 .1 D e s c r i p t i on o f d e s i g n a n d i mp l e me n t a t i o n .
I n t h i s p r o j e c t , I a d d e d p h ys i c s o b j e c t r e n d e r i n g w i t h w i r e - f r a m e b o x
i n t h e 3 D e d i t o r , t h e p h ys i c s o b j e c t c a n b e s i z e d i n t h e X , Y a n d Z b y
adjusting the 3 vectors of the matrix object. The data needed to store
those object is just a matrix: Point of origin, X -vector, Y-vector and Zvector. We can see the 3 scales on the Top Caption of the editor when we
p u s h s o m e d e f i n e d k e ys t o a d j u s t t h e s c a l e s ( s e e s c r e e n s h o t s e c t i o n ) .
W e c a n t r a n s l a t e o r r o t a t e t h e p h ys i c s o b j e c t w i t h t h e m o u s e l i k e t h e
p o l yg o n s . T h e w o r k c o d i n g p h ys i c s b o x e s a r e t o a l l o w o p e r a t i o n o n t h e
objects like are selecting, deselecting, moving, rotating, scaling,
d i s p l a yi n g a n d s a v i n g .
Saving the Physics object is done by appending the number and array
t o t h e f i l e . P o l y g o n s a n d o t h e r t yp e s o f o b j e c t s a r e s a v e d i n t h e s a m e
manner.
W e c a n p l a c e t h e P h ys i c s B o x e s a r b i t r a r i l y, w h e n l o a d e d t o t h e v i e w e r
p r o g r a m , t h e b o x e s w i l l f a l l d o w n d u e t o t h e f o r c e o f g r a v i t y. I f t h e b o x
i s p o s i t i o n e d n e a r a f l o o r p o l yg o n , i t w i l l n o t f a l l d o w n , i t w i l l s t a y
immobile until we choose to go toward it or throw a physics object.
T h e p r o g r a m h a s s e v e r a l p h ys i c s n o d e s , t h e f i r s t n o d e i s t h e
environment which has zero mass, the second is the viewer who is also a
p h ys i c s o b j e c t b u t w e d i s a b l e d i n t e r a c t i o n w i t h t h e e n v i r o n m e n t t o b e
replaced by self-made collisio n detection, the loaded physics boxes are
a l l i n d i v i d u a l n o d e s . T h e p l a ye r c a n g e n e r a t e p h ys i c s n o d e s b y p u s h i n g
t h e s p a c e b a r , t o t h r o w p h ys i c s o b j e c t s . T h e p h ys i c s i n t e r a c t i o n s o f t h e
p l a ye r a r e w i t h t h e l o a d e d a n d g e n e r a t e d p h ys i c s n o d e s o n l y.
P h ys i c s B o x d a t a s t r u c t u r e i n D e l p h i
TYPE PHYSBOX=Record
O x , O y, O z : D o u b l e ;
// Center of Box
XVecX,XVecY,XVecZ,
YVecX,YVecY,YVecZ,
ZVecX,ZVecY,ZVecZ:double; // Orthonornal Vectors
ScalX,ScalY,ScalZ: double; // Scales of the vectors
texture_ID:longint;
// Texture ID
OpjX,OpjY:double;
// 2D projection of Center Point
end;
5 .2 S c r e e n s h o t s f r o m 3 D e d i t o r .
View inside 3D editor of the scene ren dered on next slide
5 .3 Na t u r a l Co l l i s i o n d e t e c t i o n .
T h e c o l l i s i o n d e t e c t i o n b e t w e e n t h e p l a ye r a n d t h e e n v i r o n m e n t d o e s
n o t d e p e n d o n t h e N e w t o n P h ys i c s E n g i n e , i t w a s s e l f r e s e a r c h e d a n d
d e s i g n e d . T h e p r o c e s s i n v o l v e s f i l t e r i n g b y d i s t a n c e t h e p o l yg o n s t h a t a r e
t o o f a r t o t h e p l a ye r , s o t h a t w e w o n ' t p r o c e s s a l l p o l yg o n s o f t h e
environment, once filtered in, we perform the collision detection. We
c a t e g o r i z e 3 t yp e s o f p o l yg o n s w a l l , c e i l i n g a n d f l o o r . C e i l i n g a n d F l o o r
a r e a l m o s t e q u i v a l e n t . I n a l l c a s e s w e u s e t h e s c a l a r v e c t o r o f t h e p o l yg o n
w h i c h h a s b e e n p r e - c a l c u l a t e d t o i m p r o v e s p e e d . I f t h e p l a ye r ' s p o s i t i o n
a n d t h e s c a l a r c a l c u l a t e d d o t p r o d u c t s a r e a l l p o s i t i v e , t h e n t h e p l a ye r i s
i n t h e p r o x i m i t y o f t h e p o l y g o n s . O n c e e s t a b l i s h e d t h a t t h e p o l yg o n s a r e
n e a r t h e p l a ye r , t h e s p e e d v e c t o r o f t h e p l a ye r i s c h e c k e d i f i t i s c r o s s i n g
t h r u t h e p o l yg o n , w e t h e n p r o j e c t t h e s p e e d v e c t o r o n t o t h e c o l l i s i o n
vector to get its length, we then scale down the speed vector to adjust so
t h a t i t w i l l " t o u c h " e x a c t l y t h e p l a n e o f t h e p o l yg o n , w e c a l c u l a t e t h e
reflected vector, and add it to the resulting scaled down vector to get he
adjusted position. This effect is consistent with many observed
commercial video games.
6 . System eva lua t io n
6 .1 N ew t o n E v a l u a t i o n
The viewer performed as expected, we had to adjust the mass and
gravity of the engine to run it under stable condition, the Newton Engine
is not free from bugs.
I observed some strange behavior from the engine under some
conditions:
-Object passing through wall if its mass is too heavy or speed is too
high.
-If mass of object is too heav y the force of gravit y takes over the
force of friction, we see emergent phenomenon predicted in the
documentation, like as "explosion".
- I f b y m i s t a k e w e p l a c e 3 D p h ys i c s o b j e c t s c r o s s i n g i n s i d e a n o t h e r ,
the objects will bounce off as wanting to separate from the other.
- T h e e n g i n e s l o w s d o w n i f t h e r e a r e t o o m a n y p h ys i c s o b j e c t s .
6 .2 S e l f ma d e c o l l i s i o n d e t e c t io n .
I f t h e p o l yg o n s a r e w e l l e d i t e d w e s h o u l d n o t h a v e a n y p r o b l e m s w i t h
collision detection, sometime if there is a "hole" between polygons, large
e n o u g h , t h e p l a ye r c a n " p a s s t h r o u g h t h e w a l l s " . T h e s p e e d o f d e t e c t i n g
collision is efficient and fast, it uses at least 1/500 of a second (2 ms) to
process collision detection at every move.
7 . Conclusio n a nd Future wo rk
Through my activity on this project, I advanced my knowledge and
u n d e r s t a n d i n g o f u s i n g a p h ys i c s e n g i n e l i k e N e w t o n . I t p r o v i d e d m e w i t h
the opportunity to implement a difficult matter which is collision
detection.
Although it only covered a small portion of the skill needed to
i m p l e m e n t a V i d e o G a m e , I p r o g r e s s e d f r o m h yp o t h e s i s t o d i r e c t
immersion by working on this project which gave me a view of this
exciting field.
I wanted to implement many features that the 3D editor allowed, such
a s t r a n s p a r e n c y, l i g h t i n g , s h a d o w i n g . I t ' s p o s s i b l e t o u p g r a d e t h e e d i t o r
further to support arbitrary shaped objects, not only box -like. I will
continue to improve the 3D editor and Viewer on my own outside the
class project and time constraints.
8 References
[ 1 ] N e w t o n D yn a m i c s E n g i n e < h t t p : / / w w w . n e w t o n d yn a m i c s . c o m >
[2] Game engine <http://en.wikipedia.org/wiki/Game_engine >
[ 3 ] P h ys i c s p r o c e s s i n g u n i t
< h t t p : / / e n . w i k i p e d i a . o r g / w i k i / P h ys i c s _ p r o c e s s i n g _ u n i t >
[4] Rigid Body Dynamics - Chris Hecker's Website
< h t t p : / / c h r i s h e c k e r . c o m / R i g i d _ B o d y_ D yn a m i c s >
[ 5 ] A d r i a n B o e i n g ' s p h ys i c s e n g i n e l i s t
< h t t p : / / w w w . a d r i a n b o e i n g . c o m / l i n k s . h t m l # p h ys i c s >