Maniphest T100345

Cycles's Mist pass inaccurate when rendering the objects which has transparent
Closed, Duplicate
Actions

Assigned To
None
Authored By
Ding Yu (HowardBlandy)
Aug 11 2022, 12:24 PM
Tags
  • BF Blender
Subscribers
Ding Yu (HowardBlandy)
Germano Cavalcante (mano-wii)

Description

System Information
Operating system:Windows 11 Professional 21H2
Graphics card:AMD Radeon RX 6750XT(Use HIP for Cycles GPU Acceleration)

Blender Version
Broken: Release 3.2.2
Worked: Release 3.2.2

Short description of error
While rendering the scene which contains the object which has Transparent BSDF or Principled BSDF(Alpha connected to the image's Alpha to make transparent). The mist pass will calculate the transparent part of the object and make the mist inaccurate(Don't shown up in Eevee Rendering)


The glitch is showned up in blue box with arrow pointed

The compostie image
Exact steps for others to reproduce the error
Press F12 to render the image and switch to "Mist" pass and you will see the glitch
The object which caused the glitch is showned up in Viewport(Other is hidden)
VillageScene.blend41 MBDownload

Related Objects

Event Timeline

Ding Yu (HowardBlandy) created this task.Aug 11 2022, 12:24 PM
Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Needs Information from User.Aug 11 2022, 5:45 PM
Germano Cavalcante (mano-wii) added a subscriber: Germano Cavalcante (mano-wii).

I can see that there's something weird about the mist pass, but the scene is very complex and I'm not sure what should be the result.
Unfortunately the scenario described is too time consuming for us to track down, we require the bug reporter to narrow down the problem.

Normally .blend files can be simplified by removing most objects and disabling settings, until the problem reveals itself more clearly.

Also the image shown does not correspond to the one observed here:

Many bugs are fixed between the official releases. Please try the latest development snapshot of blender: https://builder.blender.org/download

Germano Cavalcante (mano-wii) added a comment.Aug 11 2022, 8:44 PM

I simplified the file to understand what is happening with the mist pass.

test.blend7 MBDownload

Apparently there is a known issue in Cycles with mist pass + transparent materials. (See T66149: Cycles semi transparent materials produce very noisy mist pass)
The file in the example shows just a variation of the same problem.
So, due of this limitation, it might be better not to use the mist pass :\

Germano Cavalcante (mano-wii) closed this task as a duplicate of T66149: Cycles semi transparent materials produce very noisy mist pass.Aug 11 2022, 8:44 PM