RGB Blackbody Node Still Broken After The Fix #98036

New Issue

Zijun Zhou · 2022-05-11T07:39:26+02:00

Zijun Zhou commented

2022-05-11 07:39:26 +02:00

System Information
Operating system: Windows-10-10.0.22000-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3050 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.15

Blender Version
Broken: version: 3.3.0 Alpha, branch: master, commit date: 2022-05-10 06:30, hash: 08a39d32a9
Worked: None

Short description of error
I have reported a bug for RGB blackbody node and the bug report was closed as a duplicate of #68926, then a "fix" was committed: 029b0df81a

But it didn't actually fix the problem. I mentioned it in #68926 but Brecht request me to yet open another bug report.

Here it is.

Exact steps for others to reproduce the error

Open the config.ocio file with any text editor, change the scene_linear role to any other spaces like XYZ and save file (I know using XYZ space as working space for light transport is a bad idea, this is just for testing purpose to make the problem pop. Any space other than Linear BT.709 should be fine to reveal the problem, just not as obvious).
Open Blender and open this .blend file:
RGB Blackbody.blend
Render it and save OpenEXR file. Import it to any software that can show you the imported file's chromaticity diagram, in my case Davinci Resolve:

You see that strange straight line there?

That's the edge of the Rec.709 triangle.

I believe this is due to the incorrect handling of 029b0df81a

Keep the existing Rec.709 fit and convert to other colorspace if needed

This is basically keeping the hardcoded Rec.709 part hardcoded, and add another hardcoded "From Rec.709" transform after it.

I believe the correct way to do it is to use the CIE XYZ for correct chromaticity and convert it to the needed RGB colorspace.

**System Information** Operating system: Windows-10-10.0.22000-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3050 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.15 **Blender Version** Broken: version: 3.3.0 Alpha, branch: master, commit date: 2022-05-10 06:30, hash: `08a39d32a9` Worked: None **Short description of error** I have reported a bug for RGB blackbody node and the bug report was closed as a duplicate of #68926, then a "fix" was committed: 029b0df81a But it didn't actually fix the problem. I mentioned it in #68926 but Brecht request me to yet open another bug report. Here it is. **Exact steps for others to reproduce the error** 1. Open the config.ocio file with any text editor, change the scene_linear role to any other spaces like XYZ and save file (I know using XYZ space as working space for light transport is a bad idea, this is just for testing purpose to make the problem pop. Any space other than Linear BT.709 should be fine to reveal the problem, just not as obvious). ![image.png](https://archive.blender.org/developer/F12926242/image.png) 2. Open Blender and open this .blend file: [RGB Blackbody.blend](https://archive.blender.org/developer/F12926246/RGB_Blackbody.blend) 3. Render it and save OpenEXR file. Import it to any software that can show you the imported file's chromaticity diagram, in my case Davinci Resolve: ![image.png](https://archive.blender.org/developer/F13066950/image.png) You see that strange straight line there? ![image.png](https://archive.blender.org/developer/F13066952/image.png) That's the edge of the Rec.709 triangle. I believe this is due to the incorrect handling of 029b0df81a > Keep the existing Rec.709 fit and convert to other colorspace if needed This is basically keeping the hardcoded Rec.709 part hardcoded, and add another hardcoded "From Rec.709" transform after it. I believe the correct way to do it is to use the CIE XYZ for correct chromaticity and convert it to the needed RGB colorspace.

Zijun Zhou commented

2022-05-11 07:39:26 +02:00

Added subscriber: @Eary

Philipp Oeser commented

2022-05-11 08:39:45 +02:00

Added subscribers: @brecht, @lichtwerk

Philipp Oeser commented

2022-05-11 08:39:45 +02:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Philipp Oeser commented

2022-05-11 08:39:45 +02:00

@brecht: this seems legit, can you share your thoughts?

Aiden commented

2022-05-23 09:07:20 +02:00

Added subscriber: @awils27

Aiden commented

2022-05-23 09:07:20 +02:00

What are your input, and output transforms set to in resolve and what is the timeline color space set to? Having any of these set to sRGB/Rec709 will hard limit the Chromaticity displayed in the scope even if the file itself contains more.