here's a (totally unbiased ;-) summary from the previous "composition rendering"
thread, intended as a discussion base:
1. Rendering happens on demand:
a) when a composition gets displayed on screen (of course)
b) on export. Here usually the full resolution gets rendered.
=> no rendering happens on saving. Only the necessary data gets written.
Exceptions can be defined according to 3.)
2. A persistent disk cache of configurable size eliminates expensive
(a cross-session cache is feasible with reasonable effort?!?)
Use case: Exporting an expensive composition for a second time should
not cause re-rendering, unless the disk cache got overwritten
in the meantime.
3. "Render Hint" operations can be inserted anywhere in a composition.
These operations have only one option: "render full resolution when saving".
This way, the user can mark intermediate results from a composition for
getting cached inside the saved composition file. These Render Hints have
no effect during editing time.
Use case: Adding a "Render Hint" operation on top of the composition makes
that a bitmap of the fully rendered composition gets included on
Use case: A Render Hint after an expensive operation (e.g. denoise) protects
the invested CPU time once the composition has been saved.
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