A drone swoops low over an alpine forest. It climbs suddenly to follow the contours of the sharply rising landscape. Pulses from its lidar—a laser mapping instrument—rapidly scan the trees below.

The forest, however, isn’t real. In fact, the entire landscape is a synthetic rendering created by University of Cambridge researchers to teach algorithms how to see trees.

The ability to recognize an individual tree in the forest canopy is essential for calculating how forests grow, how they respond to climate change and how much carbon they store. Until now, researchers developing forest vision systems would painstakingly trace the outlines of thousands of trees to provide the system with sufficient training data, a process that can take weeks.