Drawing a Crowd

In this article, we present a technique for efficiently rendering a large crowd of characters while taking steps to avoid a repetitious appearance. There are many typical scenes in games, such as large battles or stadium crowds, which require the rendering of large numbers of characters. We will describe techniques used to draw such crowd scenes, including methods for rendering multiple characters per draw call, each with their own unique animation. We will also outline tradeoffs which can be made between vertex and pixel processing in order to increase vertex throughput (the typical bottleneck in a crowd scene). Next, we will discuss a set of pixel shading tricks to allow the individual characters to have a unique look, despite being drawn from the same instanced geometry as the other characters in the scene. We will conclude with a discussion of instancing of shadow geometry.