42 I Geometry Manipulation
The system presented in this chapter tried to address many of these problems
in Rugby Challenge on PlayStation
3, Xbox 360, and PC. It begins with a
tour of the data pipeline that explains how we can accurately place seats around
the stadium and populate them with characters at runtime. A discussion of
the real-time rendering process and its problems are then laid out together with
performance evaluations that highlight the bottlenecks and potential areas for
improvement. In addition to this, we also reveal the tricks for achieving colored
“writing” in the stands, ambient occlusion that darkens the upper echelons, and
crowd density that can be controlled live in-game. Following this, we are able
to focus some discussion on the optimizations that can reduce the cost of the
system even further. The symmetrical nature of stadium architectures and their
ﬁxed seating structure allow us to make speciﬁc optimizations that we could not
do for a generic crowd system. Essentially, a complete pipeline for a fast and
ﬂexible stadium crowd simulation is presented, together with a discussion of the
problems you can expect to face when implementing this type of system.
This chapter explores the use of instancing technology, deferred rendering [Poli-
carpo 05], and imposters [Schauﬂer 95] in reducing the cost of rendering huge
crowds on the GPU without compromising the color consistency in the scene.
The system is split into two content pipelines and three rendering phases.
Each content pipeline produces data oﬄine that is then loaded at runtime and
fed into a speciﬁc rendering phase. The results of these two renders are then used
in the ﬁnal phase to shade and light the crowd area of the scene (see Figure 3.1).
The Model Content Pipeline is responsible for creating the character and
seat geometry that will be featured in the stadium. It uses our existing model
conditioner tools and exports data in an optimal format for the target platform.
Figure 3.1. Overview of the crowd rendering pipeline.