Artist-directable real-time rain rendering in city environments

In this chapter we will cover approaches for creating visually complex, rich interactive environments as a case study of developing the world of ATI "ToyShop" demo. We will discuss the constraints for developing large immersive worlds in real-time, and go over the considerations for developing lighting environments for such scene rendering. Rain-specific effects in city environments will be presented. We will overview the lightning system used to create illumination from the lightning flashes, the high dynamic range rendering techniques used, various approaches for rendering rain effects and dynamic water simulation on the GPU. Methods for rendering reflections in real-time will be illustrated. Additionally, a number of specific material shaders for enhancing the feel of the rainy urban environment will be examined.

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