Rain Stew

Freelance engine programmer Amandine Coget on the ingredients of convincing rain

Reflections

Rain creates damp, reflective surfaces, like puddles or a trenchcoat’s ‘sheen’. The glossy edges and blurring needed to replicate this effect are expensive to calculate due to the need to ‘accumulate’ light from several angles.

Light Reduction

When it rains and the sky darkens, the world has less light. Physically-based rendering now makes it easier to reuse assets under different lighting, but some previous approaches required textures to be radically changed!

So Much Code

Whether it’s raindrops, rain sheets, or splashes, VFX and particle systems require coding assistance. Code to calculate where the ground is so splashes are properly generated, layer raindrop effects in order, and so on.

Dynamicism

Turning rain effects on and off can be easy, but having the world itself (from clothing to city streets) transition smoothly between degrees of wetness is far more difficult. The field’s still undergoing research.