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Bug Gradient HDR colors are much brighter than non-Gradient colors? (Bug?)

Discussion in 'Visual Effect Graph' started by dgoyette, Jun 10, 2020.

  1. dgoyette

    dgoyette

    Joined:
    Jul 1, 2016
    Posts:
    3,821
    Here's something odd I noticed today. Maybe someone can explain why this is expected behavior, unless it's a bug.

    I found that when using "Set Color", assigning a plain old HDR color gave my particles one color/intensity, while assigning a gradient HDR color resulted in much brighter colors, even when the gradient's color stops were identical to the plain old color. Here's the bit of the graph:

    upload_2020-6-10_14-50-13.png

    So the setup is that the gradient is using the same HDR color for both of its stop that the plain old color node is using. To me, this means that the color sampled at any point in the gradient should be completely identical to the plain old color in this particular case. But the results of the two nodes is very different.

    Here's what this looks like with the plain old color:

    upload_2020-6-10_14-43-28.png

    And instead, here's what the same particle system looks like if I plug the gradient color into it:

    upload_2020-6-10_14-43-47.png

    It's massively brighter. I would have expected each particle to sample its current color from the gradient, but that the color would basically be constant, since the color is the same along the gradient.

    Does this make sense to anyone? Is this a bug with gradient colors and HDR? Or is there a good reason for this? Note that things look identical between plain old color and gradient color as long as none of the values go into the HDR range. But once they're in HDR range, it's almost like the gradient is doubling/quadrupling the intensity.
     
  2. JulienF_Unity

    JulienF_Unity

    Unity Technologies

    Joined:
    Dec 17, 2015
    Posts:
    244
    Hi! Which version are you using?
     
  3. dgoyette

    dgoyette

    Joined:
    Jul 1, 2016
    Posts:
    3,821
    This is VFX Graph 7.4, with HDRP 7.4.
     
  4. VladVNeykov

    VladVNeykov

    Unity Technologies

    Joined:
    Sep 16, 2016
    Posts:
    478
    Hi @dgoyette ,

    I believe this might be related to this issue with HDR gradients.
    In summary, we were getting different results between the color and the gradient with the same values.

    This has been fixed in the 2020.2 cycle.
     
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