OTOY Forums

Having an issue with Straight Alpha, especially with DOF blur against a bright background (eg Sky).

During rendering the object edges are treated correctly, but on completion the background environment is suddenly mixed in with the object edge as if Keep Environment is turned on (its off). This results in a halo on object edges when compositing with the alpha.

You can kill the render before it completes and retain the correct edges without those background pixels mixed in. But if it completes they get applied. Happens when rendering to the PV only. LV doesn't seem to have this issue. Oddly, if you check 'Keep Environment' with straight alpha you get double brightness at the edges - as if the environment is being added twice.

Is there a setting hidden somewhere other than the 'Keep Environment' in the Kernel? I have Alpha and Straight Alpha checked in render settings. Denoising is Off. Render Passes are off. sRGB, Tonemapped.

2020.1-RC3, R20.
If you stop it before finishing it is correct:

Thought for a moment I found a solution with 'Disable partial alpha', which fixes the background brightness being added to the edges, but it no longer stores the edge transparency in the alpha channel.

still need a workarround

Hi,
what about the Keep Environment option in Kernel settings?
If enabled, try to disable it.

ciao Beppe

bepeg4d wrote:Hi,
what about the Keep Environment option in Kernel settings?
If enabled, try to disable it.

ciao Beppe

Hi Beppe. That is already disabled - its right next to the Alpha Channel button, not easy to miss

If its not something obvious like that, its seems like this could be a real problem.

Can you share the scene with me in PM?
ciao Beppe

PMd