Graphics researchers build better rainbows

When watching or playing CGI-heavy movies and video games, it’s easy to get so caught up in the realism of the characters that you totally miss the level of detail that goes into the world around them. However for some people, improving these details is their life’s work. Researchers at the Jacobs’ School of Engineering, University of California San Diego — led by Oscar winner and Avatar graphics specialist Henrik Wann Jensen — set out to better model rainbows in computer graphics, but have come away with totally new understanding about how the arcs form. Traditionally, scientists had believed that raindrops were perfectly spherical when falling, bound to the shape by surface tension. In fact, the new research suggests that the traditional teardrop shape might not be so inaccurate, and that larger drops bulge at the bottom.

Using this new-found information, the team have been able to accurately emulate phenomena including split-double rainbows and redbows, that have before now been near imposible to create in the digital domain. The bulge in the droplets means that the light refracts differently than if totally round, so heavier rain creates different rainbows. Looking at their computer-generated images, we’re hard-pressed to tell them apart from real photos.