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Decals with emission get lit up uniformly by low-threshold bloom

Discussion in 'High Definition Render Pipeline' started by chemicalcrux, Jul 26, 2021.

  1. chemicalcrux

    chemicalcrux

    Joined:
    Mar 16, 2017
    Posts:
    726
    If I have bloom enabled in my volume profile, decals that are set to affect emission cause everything inside of them to be slightly lit up.

    This only happens if the bloom threshold is low. It also only happens if the area under the decal is being lit up enough to cause bloom, I think -- if I turn off the sun, nothing shows up, and if I use a point light instead, I have to set its intensity very high (completely blowing out the exposure) to notice it.

    This example has a solid-black emission map, so I would expect it to have zero emission at any point:

    upload_2021-7-26_13-56-25.png

    The intensity of the "extra" light is proportional to the bloom intensity. It doesn't seem to vary with the intensity of the emission, whether you set that by emission intensity or just via the map itself.

    It feels like it's applying bloom multiple times, once for each decal.

    I can't reproduce this if I make a brand-new HDRP project and mess around with the starter scene's decals -- they all behave exactly as I'd expect.

    Has anyone run into this before? I'm a little unclear where to look next. For now, I'll just set my bloom threshold to something reasonably high (as I probably should've from the start..)
     

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