A self-driving car’s view of the world often includes bounding boxes — cars, pedestrians and stop signs neatly encased in red and green rectangles. In the real world, however, not everything fits in a box. For highly complex driving scenarios, such as a construction zone marked by traffic cones, a sofa chair or other road debris in the middle of the highway, or a pedestrian unloading a moving van with cargo sticking out the back, it’s helpful for the vehicle’s perception software to provide a more detailed understanding of its surroundings.