We don’t have documentation for all of the cache trigger reasons. One of the reasons the cache can miss due to scene changes is heuristic scene-dependent variable specialization. If you’re in a position to share a reproducer privately, we could examine and report back on the exact reason for the unexpected cache miss. (The reproducer can be either in the form of a binary, or in the form of an OptiX trace capture.)
Is it feasible in your case to warm your cache with the exact same scene that will be rendered, or are you hoping and expecting to support scene changes without any recompilation? Depending on what you need, there may be additional guidance we can offer.
Obligatory plug for upgrading to OptiX 7 at some point. I’m sure you’re aware so forgive me, but for what it’s worth, the caching behavior in OptiX 7 is more controllable, predictable, and transparent from a user perspective, since you control specialization explicitly, and OptiX 7 doesn’t know anything about your scene structure at compile time. This is among other reasons why OptiX 7 can be easier to optimize.
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David.