Cycles Multi Device Scheduling

Overview

When rendering on multiple devices, the image is horizontal in even parts. As more samples are rendered, the size of each part is rebalanced according to the performance of the device, and render buffers are moved between devices as needed.

This scheduling algorithm is to be improved in the future, as load balancing can be poor with few samples or in interactive rendering. For long offline renders, or repeated viewport renders, rebalancing works well.

Details

TODO

Possible Improvements

• Render alternating scanlines or strips on different devices, for even distribution in interactive rendering without rebalancing, at the cost of coherence.
• Find a better balancing algorithm for low number of samples when devices have very different performance.