Transparency and Emission Does not Render Correctly on Transparent Background #74447

New Issue

Tom Wright · 2020-03-04T21:48:55+01:00

Tom Wright commented

2020-03-04 21:48:55 +01:00

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 441.66

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-02-12 16:20, hash: 77d23b0bd7
Worked: (optional)

Short description of error
When rendering an emissive transparency on top of a transparent background (either Eevee or Cycles) the transparent object's material color becomes completely desaturated. This only happens in the render (F12) not in the viewport camera.

Exact steps for others to reproduce the error
In Render Properties, go to Film and turn on Transparency.
Create a sphere, add a mix shader with transparent and emissive and make it mostly transparent to see the results better (Factor of .05 or so).
Crank the emissive node up to maybe 50 and give it a color 1,0,0 for pure red.
In viewport camera, you see what you would expect, a red-ish emissive sphere with some transparency. When rendered however, the sphere will be almost completely desaturated of color.
Turn on bloom in Eevee to get the effect even more.
In the viewport, you will see the bloom and it look as it should but when rendered, no bloom and no color.

In this image, the left version is rendered with a transparent background and composited in, the right is rendered with the background in place (no alpha).
https://imgur.com/a/3swdIuf

**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 441.66 **Blender Version** Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-02-12 16:20, hash: `77d23b0bd7` Worked: (optional) **Short description of error** When rendering an emissive transparency on top of a transparent background (either Eevee or Cycles) the transparent object's material color becomes completely desaturated. This only happens in the render (F12) not in the viewport camera. **Exact steps for others to reproduce the error** In Render Properties, go to Film and turn on Transparency. Create a sphere, add a mix shader with transparent and emissive and make it mostly transparent to see the results better (Factor of .05 or so). Crank the emissive node up to maybe 50 and give it a color 1,0,0 for pure red. In viewport camera, you see what you would expect, a red-ish emissive sphere with some transparency. When rendered however, the sphere will be almost completely desaturated of color. Turn on bloom in Eevee to get the effect even more. In the viewport, you will see the bloom and it look as it should but when rendered, no bloom and no color. In this image, the left version is rendered with a transparent background and composited in, the right is rendered with the background in place (no alpha). https://imgur.com/a/3swdIuf

Tom Wright commented

2020-03-04 21:48:55 +01:00

Added subscriber: @ThomasWright

Evan Wilson commented

2020-03-04 23:47:42 +01:00

Added subscriber: @EAW

Evan Wilson commented

2020-03-04 23:47:42 +01:00

The image in the link above.

![F2A2AB09-9D2C-4C93-862B-A4B9B9139D4E.jpeg](https://archive.blender.org/developer/F8388713/F2A2AB09-9D2C-4C93-862B-A4B9B9139D4E.jpeg) The image in the link above.

Richard Antalik commented

2020-03-05 04:10:28 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-03-05 04:10:28 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Richard Antalik commented

2020-03-05 04:10:28 +01:00

Can you please upload simple .blend file demonstrating this?

Robert Guetzkow commented

2020-03-05 10:27:46 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2020-03-05 10:27:46 +01:00

Based on the description this could be a duplicate of #52680

Brecht Van Lommel commented

2020-03-05 11:16:44 +01:00

Added subscriber: @brecht

Brecht Van Lommel commented

2020-03-05 11:16:44 +01:00

Changed status from 'Needs User Info' to: 'Archived'

Brecht Van Lommel closed this issue

2020-03-05 11:16:44 +01:00

Brecht Van Lommel self-assigned this 2020-03-05 11:16:44 +01:00

Brecht Van Lommel commented

2020-03-05 11:16:44 +01:00

Yes, it's the same issue as #52680 (Alpha difference Viewport/F12 ).

In general if you want to use that image for compositing in other software, you need to save it in a file format like OpenEXR which supports emission without opacity, which e.g. PNG does not support.

Yes, it's the same issue as #52680 (Alpha difference Viewport/F12 ). In general if you want to use that image for compositing in other software, you need to save it in a file format like OpenEXR which supports emission without opacity, which e.g. PNG does not support.

Tom Wright commented

2020-03-09 01:06:43 +01:00

Thank you! Yes, the OpenEXR works perfectly. Just have to Gamut back to sRGB.

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Transparency and Emission Does not Render Correctly on Transparent Background #74447