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					 Physics for Animation Artists



                                       Alej Garcia* (Physics)
                                      Dave Chai (Art & Design)
                                       San Jose State Univ.


                                                   Supported by the
                                                   NSF/CCLI program
*Presenting at AAPT Winter 2009 meeting, Chicago
Animation
Three basic types of animation:




   Four of the top 10 grossing movies in
   2008 were animated feature films
   (WALL-E, Kung-Fu Panda, Madagascar 2,
   and Horton Hears a Who!).
Traditional       Computer           Stop-motion

       As kids we knew these as “cartoons.”
Animation-related Work
Animation is also important in:
                   Top money movies of 2008 were Dark Knight,
                   Iron Man, and Indiana Jones (each had over
                   $300 million in domestic gross)
                                                       Video Games




        CGI for live-      Guitar Hero III sales topped $1 billion in the
        action films       2008 holiday season.
   Silicon Valley & SJSU




San Jose State is located in
Silicon Valley at the south
end of San Francisco Bay
Animation Program at SJSU
The Animation / Illustration program in San Jose
State’s School of Art & Design has 5 permanent
faculty, a dozen lecturers and over 400 majors.
Physics for Animators
To create realistic animations, animators need
  to understand principles of physics.
Anatomy for Artists
Surgeons and artists
learn anatomy, but
for very different
purposes.
Engineers and artists
need different
curricula in physics
for their disciplines.

                         Leonardo da Vinci
Teaching Physics to Animators
For three semesters Dave Chai and I have been
team teaching an upper-division animation class.




                                     Prof. Dave Chai,
                                     Award-winning
                                     animator
Animation Exercises
Animation is learned by exercises of varying
 difficulty. The simplest is a bouncing ball;
 an intermediate exercise is a human jump.


                                          Play
                                          Movie

                                          Play
                                          Movie
Ball Drop               Time      Frames   Distance from
                        (sec)              apex

The first exercise      1/
                             24   1        1/
                                                3   inch

is the ball drop,       1/
                             12   2        1 1/3 inches
which introduces
                        1/        3        3 inches
constant                     8


acceleration.           1/
                             6    4        5 1/3 inches

                        ¼         6        1 foot
We discuss the
timing and spacing
                        1/        8        1 ¾ feet
                             3


of the motion, such     ½         12       4 feet
as in this example      2/        16       7 feet
of a falling softball
                             3



(4 inch diameter)       ¾         18       9 feet

animated “on twos.”     1         24       16 feet
A Fourth Down at Half Time
                                       In time, Key #3 is
                                       half way between
                                       #1 and #5.

                                       In space, Key #3
                                       is a fourth of the
                                       way down between
                                       #1 and #5.

                                       This rule always
                                       applies for any key
                                       half-way in time
                                       from the point of
 3 frames per key   6 frames per key   release.
     (close-up)      (medium shot)
Timing a Jump
This jump looks to be about 12 inches in the air,
which takes a total of 12 frames (6 from take-
off to apex and 6 from apex to landing).
             #2          #3
                                #4        Frame   Key
        #1                           #5
                                          1       #1
                                          2       |
             X       X                    3       |
                               X
    X                                X    4       #2
                                          5       |
                                          6       |
                                          7       #3
                                          8       |
             X = Center of Gravity
Timing the Jump
                                Frame 78

 This jump looks to be
 about 12 inches high.       Play
                             Movie

The jump has 4 frames
from take-off to apex          Frame 82

and 5 frames from apex
to landing.

The height of the jump,
given the time in the air,     Frame 87
should only be about 6-8
inches.
 Path of Action
As with bouncing
ball, the path of
action is a
parabolic arc.
Apex needs to
be above the
half-way point
between take-
off and landing
Parabolic Arc in Perspective

                          Maximum height
                          (ball at midpoint)


                                               VP
                                                    HL




                Ball starts and ends
                on the ground.
Parabolic Arc in Perspective (cont.)


      1


                                            VP
                                                    HL


  3



                    Use “Fourth Down at Half
                    Time” to fill in more points.
       Apex of a Jump
Apex

       Correct
  Animation Physics Website
For more info, visit:

www.AnimationPhysics.com

				
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posted:11/26/2011
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