1. Instancing doesn't reduce the complexity of rendering a scene in terms of light transport, it only reduces the memory storage and Accel structure complexity.

1. Instancing doesn't reduce the complexity of rendering a scene in terms of light transport, it only reduces the memory storage and Accel structure complexity. Actually, a forest with occluding foliage geometry is a quite difficult light transport situation: it's very difficult for next event estimation to work efficiently, so therefore most of the lighting is indirect and therefore is quite noisy, as it's difficult to find the environment / IBL light for the sun. Portal guiding and NEE guiding can help a bit, but it can still be quite slow.