Maniphest T80746

Image blur in compositor creates halo from alpha
Closed, ResolvedBUG
Actions

Assigned To
Jeroen Bakker (jbakker)
Authored By
Daniel Bystedt (dbystedt)
Sep 13 2020, 3:49 PM
Tags
  • BF Blender (2.91)
  • EEVEE & Viewport
  • Compositing
Subscribers
Clément Foucault (fclem)
Daniel Bystedt (dbystedt)
Jeroen Bakker (jbakker)
jeroen holterbosch (jeroen)

Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.59

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-11 09:14, hash: rB1b6dd42803df
Worked: Worked: 2.91.0 Alpha, Hash 4ccd5bf5c658, date 2020-09-09 10:38
This is likely related to D8234: Use DrawManager for Image/UV Editor

Short description of error
When i render objects with [render settings > film > Transparent = True] (bpy.context.scene.render.film_transparent = True), and blur the rendered image in the compositor, I get a strange halo around the objects. This seems related to the blurred alpha. If I sample the pixel values of the halo in the image editor, the pixel values that I observe (bright) is not the same as the sampled pixel values (black)

Exact steps for others to reproduce the error

  1. create some objects in the 3d view and frame them in the camera
  2. set [render settings > film > Transparent = True]
  3. Render the image
  4. open the compositor and set [use nodes = True]
  5. Connect render layers.image > blur > viewer
  6. look at the viewer node in the image editor
  7. Increase the blur of the blur node in the compositor and observe the halo around the objects

Jeroen Bakker messaged me on blender.chat and asked me to test the new submit D8234: Use DrawManager for Image/UV Editor, so I'm pinging @jeroen holterbosch (jeroen) Bakker (jbakker) and @Clément Foucault (fclem) to this bug report

debug_D8234_blur_compositor_halo_v001.blend1 MBDownload

Revisions and Commits

rB Blender
rB78ea6302f1c4 Fix T80746: Image blur in compositor creates halo from alpha
rBf492c8d488b7 Image Editor: Make Rendering of Pure Emissive Colors Optional

Related Objects

Event Timeline

Daniel Bystedt (dbystedt) created this task.Sep 13 2020, 3:49 PM
Daniel Bystedt (dbystedt) added a subscriber: Clément Foucault (fclem).Sep 13 2020, 3:58 PM
Jeroen Bakker (jbakker) added a subscriber: Jeroen Bakker (jbakker).Sep 14 2020, 8:36 AM

The cause of the halo is that the pixels samples contain some anti aliasing colors, but the alpha channel is 0.0. As it is 0.0 the pixel will be shown as pure emissive color. Depending on the solution of T80745 we might want to add an option to the compositor output nodes how the image should be treated.

Jeroen Bakker (jbakker) changed the task status from Needs Triage to Confirmed.Sep 14 2020, 8:37 AM
Jeroen Bakker (jbakker) claimed this task.
Jeroen Bakker (jbakker) edited projects, added BF Blender (2.91), EEVEE & Viewport, Compositing; removed BF Blender.
Jeroen Bakker (jbakker) changed the subtype of this task from "Report" to "Bug".
Jeroen Bakker (jbakker) added a commit: rBf492c8d488b7: Image Editor: Make Rendering of Pure Emissive Colors Optional.Sep 15 2020, 1:45 PM
Jeroen Bakker (jbakker) closed this task as Resolved by committing rB78ea6302f1c4: Fix T80746: Image blur in compositor creates halo from alpha.Sep 15 2020, 2:19 PM
Jeroen Bakker (jbakker) added a commit: rB78ea6302f1c4: Fix T80746: Image blur in compositor creates halo from alpha.
Jeroen Bakker (jbakker) mentioned this in T80745: Texture painting - Erase alpha creates dark halo around alpha.Sep 15 2020, 2:34 PM