Real-Time Rendering, Third Edition, 3rd Edition

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Chapter 19

The Future

“Pretty soon, computers will be fast.”

—Billy Zelsnack

“Prediction is difficult, especially of the future.”

—Niels Bohr or Yogi Berra

“The best way to predict the future is to create it.”

—Alan Kay

“I program my home computer,

beam myself into the future.”

—Kraftwerk

There are two parts to the future: you and everything else. This chapter is

about both. First, we will make some predictions, a few of which may even

come true. More important is the second part of this chapter, about where

you could go next. It is something of an extended Further Reading and

Resources section, but it also discusses ways to proceed from here—sources

of information, conferences, programming tools, etc.

19.1 Everything Else

One yardstick of progress is how closely interactive applications can ap-

proach offline rendered images. Films such as Pixar’s Ratatouille and PDI’s

Shrek series use render farms chock full of racks of CPUs, around 3100 cores

in all, each with access to 16 GB of memory. For example, for Ratatouille,

a single frame took an average of 6.5 hours, though complex shots could

take tens of hours. One constraint is the number of primitives. Scenes

with swarms of rats have hundreds of millions of hairs in them [1093]. All

the assets—models, textures, shaders, precomputed lighting—totaled 5 ter-

abytes, all of which had to be available to the network at all times. At one

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880 19. The Future

point, network traffic was a major bottleneck for the film Cars,notCPU

processing power [613].

Going from 300+ minutes per frame to 30 frames per second is a chal-

lenge. On one level, current games can claim levels of visual complexity

near that of Toy Story. This perhaps is not quite true, as the texture de-

tail, geometry tessellation, and amount of sampling per pixel is higher

in Toy Story than in any game. RenderMan is a microgeometry ren-

derer at heart, with each surface chopped into polygons smaller than a

pixel [31, 196]. Such fine tessellations are rarely used in interactive appli-

cations because of the cost. Effective resolution, in terms of total number

of samples taken per pixel multiplied by total number of pixels, is a mag-

nitude or two higher in films than at playable frame rates for video games.

That said, a case can be made that for some shots, at relatively low res-

olution (so that antialiasing can be used), Toy Story complexity has been

achieved.

Say that with the latest GPUs we are only a factor of 100 away from

achieving a decent frame rate at a fine level of detail and shading for most

scenes. Moore’s Law gives an acceleration rate of 2 times every 1.5 years, or,

more usefully, about 10 times every 5 years [1198]. So by this measure, we

are only a decade away from achieving this goal. Unfortunately, it does not

appear that processor speed will be the main constraint on computing in

the future. Bandwidth is increasing by only around 25% per year, a rise of

a little more than 3 times every 5 years. This makes a hundred-fold increase

take about 20 years instead of 10, as long as some other bottleneck does

not appear. Also, the goal line has moved: Ratatouille took 420 times the

computing resources that Toy Story did [613]. On one level, it is incredible

to see what has been done in the area of interactive rendering, such as

Figures 19.1 and 19.2. On another, there is still a lot more processing that

can be done.

Graphics helps sell games, and games help sell chips. One of the best

features of real-time rendering from a chipmaker’s marketing perspective is

that graphics eats huge amounts of processing power and other resources.

As discussed at the beginning of Chapter 14, hardware constraints such as

frame rate, resolution, and color depth all can grow to some extent. The

direction that is essentially unbounded is complexity. By complexity, we

mean both the number of objects in a scene and the way these objects are

rendered. Ignoring all other directions for growth, this single factor makes

graphics a bottomless pit for processing power to fill. The depth complexity

of scenes will rise, primitives will get smaller, illumination models will

become more complex, and so on. First, build a model of the place where

you are right now, down to the tiniest details, and then create shaders

that create a photorealistic rendering of that environment. Add shadows,

then glossy reflections. Now, model the surroundings with the same detail.

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19.1. Everything Else 881

Figure 19.1. Realistic and artistic interactive renderings. (Image above from “Crysis,”

courtesy of Crytek [887, 1342], image below from “Okami,” courtesy of Capcom Enter-

tainment, Inc.)