Introduction to photorealism
What is photorealism?
Photorealism simply means that a simulated scene appears indistinguishable from a photograph, or by extension, from real life. The main obstacle to photorealism is processing power, said Jensen.
To make movies like "Avatar" and "Life of Pi" appear photorealistic, each frame of the movie is pre-rendered. That means that the digital models and scripted motion in a virtual scene are compiled into frames (usually up to 30 frames per second) and touched up, a process that can take hours per frame.
But video games don't have that kind of time. Because the action in a scene has to respond dynamically to player input, video games have to render their graphics in real time, usually at a rate of 60 frames per second.
That's why it's good to be skeptical of pre-rendered video game trailers. They inevitably look better than the final game, because they are essentially movies, not samples of how the game looks when you play it.
Currently, during actual play, games use a technique called rasterization to achieve somewhat realistic effects. Rasterization is an algorithm by which three-dimensional shapes are output for display on a flat screen.
Developers have had to find roundabout ways to create realistically lighted scenes, because rasterization is not modeled after the way visuals work in the real world.
For example, the best way to do shadows with rasterization in game engines like Unity is to texture an object with a darker filter, which recreates the appearance of shadow. The light sources in the scene aren't dynamically creating the shadow like a spotlight on a stage would; instead, you're drawing in the shadow yourself, like an artist doing a sketch.
The games industry is in the middle of a transition from rasterization to ray tracing, Jensen said. Unlike rasterization — which demands that designers hand-create effects like shadows, textures and shades of color — ray tracing works in a way that closely models the natural world.
Ray tracing means less work for artists and developers, not to mention a more realistic finished product. But it also means a lot more work for the computer: the amount of processing power needed to account for every light ray is enormous.