Meta-issue: testrender wish list

[lgritz]

Master list of testrender feature requests

We will use this issue to collect individual suggestions or feature requests for testrender. Some are larger projects that can be later forked off to their own issues, but some are as small as single-day tasks for newcomers.

Please comment/reply on this ticket to request that items be added (or if you're on the TSC or have permissions to edit this description, feel free to do so.

Comment/reply to say "hey, I want to do task X" so that multiple don't independently attempt the same tasks (if it's something where only one can really be accepted); we don't want anybody's work time to be wasted.

Good First Issues

These are small tasks ideal for newcomers to the project, suitable for Dev Days. They don't really require knowledge of how OSL itself is implemented under the covers, but having written a student project sized path tracer might be helpful (since that's basically what testrender is).

- [ ] Create a test scene based on the USD standard shaderball

Intermediate projects

These will require more extensive experience with theory and practice of writing renderer, or perhaps more knowledge of OSL internals, or take longer than first-issue projects.

- [ ] Add displacement shader support to testrender
- [ ] Fix uv derivatives in testrender

Advanced projects

Items expected to take an extended effort (say, many weeks), or require a level of expertise of someone who has written a production complexity renderer before.

- [ ] Implement support for subsurface scattering
- [ ] Implement support for medium closures (volumetric rendering)