1.5.1 - CoronaRegion Alpha being lost when ClearVFB is disabled

[alexyork]

Hi folks, we're finding issues with alpha channels in 1.5.1.

Problem:
With Clear VFB disabled:
Step 1) render one corona region - beauty and alpha channel are correct, of course
Step 2) render a new corona region somewhere else - beauty is correct, but old alpha channel is lost - new alpha is correct

Problem doesn't happen when you carry out the same process using max regions, only corona regions.

So in other words, CoronaRegion is not respecting old alpha channel renders when ClearVFB is disabled.

With ClearVFB enabled it behaves as expected.

[romullus]

Duplicate: https://forum.corona-renderer.com/index.php/topic,12360.0.html