# Objective
If multiple cameras render to the same target with MSAA enabled, only
the first and the last camera output will appear in the final output*.
This is because each camera maintains a separate flag to track the
active main texture. The first camera renders to texture A and all
subsequent cameras first write-back from A and then render into texture
B. Hence, camera 3 onwards will overwrite the work of the previous
camera.
\* This would manifest slightly differently if there were other calls to
post_process_write() in a more complex setup.
The is a functional regression from Bevy 0.12.
## Solution
The flag which tracks the active main texture should be shared between
cameras with the same `NormalizedRenderTarget`. Add the
`Arc<AtomicUsize>` to the existing per-target cache.
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