Blend Between Lightmaps at Runtime

[mdwigley]

Detailed Description

The ability to linearly interpolate between two previously baked lightmaps that have been stored on a prefab. This should be as performant as possible while allowing this interpolation ratio to be changed at runtime via scripting, animations and/or the timeline.

Context

Often you not only will want to have different baked lightmaps but you will want the lighting situation to transition between two states. The most obvious example would be transitioning between day/night cycles.

Possible Implementation

Either through threaded tasks or a shader?

[mdwigley]

Proposal

Shader v.s. Lighting Data

For this feature to be shader invariant, I believe the lighting data will need to be modified instead of a project-dependent custom shader since it would be hard to create a shader to suit all purposes. By providing this information via the "Lighting Data" any shader will be able to access it.

Operation Scope

Another consideration is that, by design, the exported prefab "Lighting Data" is packaged so that the prefab is not dependent on a master image folder for its lightmap contents. Additionally, this feature should allow for a single prefab to be updated independently of others. Consequently, interpolation should happen on a prefab level while allowing for both a local and global "mode" (where the local uses a temporary additional lightmap while the global mode modifies the "Lighting Data" lightmap directly).

Jobs and Burst

While the calculation for the interpolation should be fast, the sheer number of operations will be a limiting factor. In my opinion, this can be (at least partially) mitigated by using jobs and the burst compiler. It also may be limited to higher quality settings where sufficient resources are assumed to be available.