Appleseed 2.0 has been released, and they included a new Adaptive Sampling technique, they say it´s more efficient than their old one, and since Appleseed and Cycles are Open Source, maybe there is not problem to pick some parts of that improvement to finally have Adaptive Sampling implemented in Cycles.
Here is the link to the GSoc 2018 github of the person who did it:
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# Final Report - Google Summer of Code 2018
## Adaptive Image Plane Sampling and Resumable Rendering for appleseed
I was lucky to participate in GSoC 2018 and spend my time on the physically-based renderer named appleseed. I took care of 2 different rendering projects. I successfully finished the first project (adaptive sampling) and the second one is waiting to be merged. Briefly, the goal of adaptive sampling is to spend more rendering time on complicated areas of an image rather than spending the same time in all areas. And resumable rendering allows to save the state of the renderer after each rendering pass to be able to restore from that point. You can take a look at the [original proposal](appleseed-proposal.md). All the code that I wrote was **merged into master and will be available for the next release**, except resumable rendering's whose review is pending.
### Community bonding period and before
Before GSoC started, I made some pull requests that were merged into master to get familiar with the code base.
- [Let frame/tile/pixel engines print their parameters when rendering starts](https://github.com/appleseedhq/appleseed/pull/1859)
- [Don't reset trackers when sampling is finished](https://github.com/appleseedhq/appleseed/pull/1862)
- [Save extra AOVs](https://github.com/appleseedhq/appleseed/pull/1865)
- [Wire up correctly OSL's printf() to the renderer's logger](https://github.com/appleseedhq/appleseed/pull/1881)
- [Create a diagnostic AOV for invalid samples](https://github.com/appleseedhq/appleseed/pull/1888)
- [Allow sending AOV tiles to stdout](https://github.com/appleseedhq/appleseed/pull/1906)
- [Export main aovs instead of extra aovs](https://github.com/appleseedhq/appleseed/pull/1954)
- [Implement Correlated Multi-Jittered Sampling](https://github.com/appleseedhq/appleseed/pull/1975)