Trans RINA, Vol 153, Part C1, Intl J Marine Design, Jul - Dec 2011
Minimum time to render a frame of film
Maximum time to render a frame of film
Total Frames
Size Of Completed Film
Size of Pixar’s Render Farm (Running 24/7)
45 minutes 20 Hours
110,000 500 GB
100 Sun Workstations
Table. 1: Statistics for Toy Story animation [2]
It is not enough to use computer graphics to generate a static scene, objects in the scene have to move - they have to behave. Making computer-generated objects and characters behave in realistic ways poses several quite distinct problems:
behaviour of fluids (liquids and gases) complex, textured, flexing surfaces motion of groups (flocks, herds and schools) and ensembles (snow flakes, rain drops, leaves)
Features such as waves and ripples in liquids, flames and smoke, clouds and fog, have all become easier to create as computer power has increased. One difficult problem has been reproducing the flexing of complex surfaces such as the skin of the face or clothing [3]. Modelling a plastic toy such as Toy Story's Buzz Lightyear, whose facial expressions are largely limited to movements of large features such as eyes, mouth and chin, is relatively simple. By contrast, trying to model a humanoid face such as Shrek's requires an extremely complex model of the underlying facial musculature. Even Woody's face had over 200 features that an animator could control.
While final rendering takes a great deal of computer time, it is perfectly possible to view real-time animations during the design phase, not only as simple wire-frame models, but as simplified versions of the final product. This makes it quite easy to experiment with alternatives. For example, the computer model incorporates details of the position of lights and cameras as well as the objects, characters and backgrounds in the scene, so the former can be changed without any need to redraw characters or backgrounds. This leads to one of the key differences between CGI and conventional animation - the ability to move the camera in an extremely dynamic fashion - something that is particularly notable in Pixar's films [4].
Not all objects in a CGI scene are rendered using standard ray tracing techniques. Particle systems are used to model things like fire, smoke, fireworks and the leaves of trees. Such features consist of a very large number of objects, all of which behave in a similar way. Ray tracing collections of many thousand such objects would require enormous computer power (even by today's standards), so special techniques have been developed to deal with them [5]. The motions of the individual 'particles' in such
a system are typically quite complex, since they are often acting
under various
constraints. For example, the
behaviour of the leaves of a tree swaying in the wind are determined by the wind (which may be gusting), the elasticity of the branches of the tree and gravity, the detailed, individual way they are attached to branches and the movement of those branches themselves. While the computations involved may be complex, computers now make it possible to produce realistic animated images of such scenes.
5. MOORE’S LAW AND PROCESSOR COMPLEXITY
The continued increase in the number of transistors that can be fabricated on a single 'chip', a trend known as Moore's Law, has been the primary driving force in the significant changes in computer performance for more than thirty years. In 1965 Gordon Moore, co-founder of Intel, predicted that the number of gates (transistors) that could be put on a single integrated circuit would double every eighteen months, or put another way, would go up by a factor of 1000 every 15 years [6]. The 'law' has held for over 35 years, as shown in Table. 2 below.
Intel Processor
4004 8008 8080 8086 286 386
486 DX Pentium
Pentium II Pentium III Pentium 4 Itanium 2
Core 2 Duo Core i7 (quad)
10-core Xeon Westmere
Year Of Production
1971 1972 1974 1978 1982 1985 1989 1993 1997 1999 2000 2003 2006 2008 2011
2,250 2,500 5,000
29,000
120,000 275,000
1,180,000 3,100,000 7,500,000 24,000,000 42,000,000 220,000,000 291,000,000 731,000,000 2,600,000,000
Table.2: Number of transistors that can be fabricated on a single 'chip'
As gates get smaller, they operate faster, since the signals have less distance to travel. Since the fabrication cost of an integrated circuit is not directly related to the number of gates (in essence the process is a kind of photographic etching), this means that while hardware prices have remained roughly
increases in performance. Moore's Law has been directly responsible
for the
constant, there reduction in
have the
been large number of
components needed to build electronic devices. This ©2011: The Royal Institution of Naval Architects C-41 Transistors
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