Add Transparent BSDF Shader over Emission Shader Alpha export issue #103934

New Issue

Jan-Erik · 2023-01-17T11:09:42+01:00

Jan-Erik commented

2023-01-17 11:09:42 +01:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 522.30

Blender Version
Broken: version: 3.4.1, branch: blender-v3.4-release, commit date: 2022-12-19 17:00, hash: 55485cb379
Worked: (newest version of Blender that worked as expected)

Short description of error
When you render an image with semi transparent emission shader, the alpha information gets lost when you save the image. In the viewport it is displayds properly.
This worked for me in older versions of blender

xray_Bug.blend

Exact steps for others to reproduce the error
When you add a transparent shader over an emission shader with layer weight plugged in strength, the viewport and the final saved image differ.

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 522.30 **Blender Version** Broken: version: 3.4.1, branch: blender-v3.4-release, commit date: 2022-12-19 17:00, hash: `55485cb379` Worked: (newest version of Blender that worked as expected) **Short description of error** When you render an image with semi transparent emission shader, the alpha information gets lost when you save the image. In the viewport it is displayds properly. This worked for me in older versions of blender ![grafik.png](https://archive.blender.org/developer/F14158725/grafik.png) ![transparent_test.png](https://archive.blender.org/developer/F14158728/transparent_test.png) ![grafik.png](https://archive.blender.org/developer/F14158733/grafik.png) [xray_Bug.blend](https://archive.blender.org/developer/F14158731/xray_Bug.blend) **Exact steps for others to reproduce the error** When you add a transparent shader over an emission shader with layer weight plugged in strength, the viewport and the final saved image differ.

Jan-Erik commented

2023-01-17 11:09:42 +01:00

Added subscriber: @JanErik

Richard Antalik commented

2023-01-17 21:13:07 +01:00

Closed as duplicate of #81199

Richard Antalik closed this issue

2023-01-17 21:13:07 +01:00

Jan-Erik commented

2023-01-18 10:36:12 +01:00

Added subscriber: @richard-27

Jan-Erik commented

2023-01-18 10:36:12 +01:00

This comment was removed by @JanErik

*This comment was removed by @JanErik*

Richard Antalik was assigned by Jan-Erik

2023-01-18 10:39:34 +01:00

Richard Antalik was unassigned by Jan-Erik

2023-01-18 10:40:27 +01:00

Jan-Erik commented

2023-01-18 10:40:27 +01:00

Added subscriber: @iss

Jan-Erik commented

2023-01-18 10:42:57 +01:00

This is not only bloom/emission related

This is not only bloom/emission related ![grafik.png](https://archive.blender.org/developer/F14171144/grafik.png) ![grafik.png](https://archive.blender.org/developer/F14171147/grafik.png) ![grafik.png](https://archive.blender.org/developer/F14171151/grafik.png)

Evan Wilson commented

2023-01-18 16:08:44 +01:00

Added subscriber: @EAW

Evan Wilson commented

2023-01-18 16:08:44 +01:00

Thank you for the report @JanErik.

This is occurring because you are using the PNG format, which doesn't support associated ('premultiplied') alpha. If you switch the rendered image to only show the alpha
channel, you will see that there is nothing where the sphere is. The PNG specification says that any pixels with zero alpha must have their color channels also set to zero when saving a PNG file

That is why this is a duplicate of #81199 (Some effects [bloom, smoke, fire, ..] still don't save in PNG with transparent background (occlusion vs. emission)) and #81390 (Blender 2.91.0 Alpha - Blender cannot export proper image when containing smooth gradient of Alpha).

Thank you for the report @JanErik. This is occurring because you are using the PNG format, which doesn't support associated ('premultiplied') alpha. If you switch the rendered image to only show the alpha channel, you will see that there is nothing where the sphere is. The PNG specification says that any pixels with zero alpha must have their color channels also set to zero when saving a PNG file That is why this is a duplicate of #81199 (Some effects [bloom, smoke, fire, ..] still don't save in PNG with transparent background (occlusion vs. emission)) and #81390 (Blender 2.91.0 Alpha - Blender cannot export proper image when containing smooth gradient of Alpha).

Jan-Erik commented

2023-01-18 17:11:40 +01:00

Thank you @EAW, I was irritated bcause the bug report it was merged in, mentionend specifically (occlusion vs. emission).
But anyways I tried also Tiff, WebP and EXR, they also dont work. Is there any format, that supports this premuliplied alpha?

Thank you @EAW, I was irritated bcause the bug report it was merged in, mentionend specifically (occlusion vs. emission). But anyways I tried also Tiff, WebP and EXR, they also dont work. Is there any format, that supports this premuliplied alpha?

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Add Transparent BSDF Shader over Emission Shader Alpha export issue #103934