Cycles plane Emission gradient "clipping" #117771

New Issue

Emre Can Özcan · 2024-02-02T22:50:19+01:00

Emre Can Özcan commented

2024-02-02 22:50:19 +01:00

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3080/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.58

Blender Version
Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: 9be62e85b727
Worked: (newest version of Blender that worked as expected)

Short description of error
I have never encountered this kind of light behavior before, I have used this setup multiple times and never had something like this

Exact steps for others to reproduce the error
Open the attached Blend file
when using cycles the light behaves very strangely, like there is a cutoff by a set distance on the X-axis

Thank you in advance Blender Developers & anybody involved I truly appreciate the hard work and efforts!
(excuse me if there is any obvious mistake from my side or a setting that I overlooked)

**System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3080/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.58 **Blender Version** Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: `9be62e85b727` Worked: (newest version of Blender that worked as expected) **Short description of error** I have never encountered this kind of light behavior before, I have used this setup multiple times and never had something like this **Exact steps for others to reproduce the error** Open the attached Blend file when using cycles the light behaves very strangely, like there is a cutoff by a set distance on the X-axis Thank you in advance Blender Developers & anybody involved I truly appreciate the hard work and efforts! (excuse me if there is any obvious mistake from my side or a setting that I overlooked)

Bug Report.blend

1.4 MiB

2024-02-02_22-38-18.mp4

50 MiB

Emre Can Özcan added the

labels 2024-02-02 22:50:20 +01:00

Emre Can Özcan changed title from ~~Plane Gradient Emission Clipping~~ to Cycles plane Emission gradient "clipping"

2024-02-02 22:51:02 +01:00

Alaska commented

2024-02-03 01:22:24 +01:00

I can confirm that emissive planes are rendering incorrectly in the attached file.

Running some quick tests, it seems this issue was introduced in Blender 3.3. However a similar issue can still be reproduced back to Blender 2.80 and probably earlier. I'm not sure if this "similar" issue is the same one. So I will do further investigating before reporting on it.

I can confirm that emissive planes are rendering incorrectly in the attached file. Running some quick tests, it seems this issue was introduced in Blender 3.3. However a similar issue can still be reproduced back to Blender 2.80 and probably earlier. I'm not sure if this "similar" issue is the same one. So I will do further investigating before reporting on it.

Alaska added

and removed

labels 2024-02-03 01:22:41 +01:00

Alaska commented

2024-02-03 03:38:45 +01:00

It seems like the issue was introduced with 38af5b0501

CC @brecht

Just for reference, here's what I observed:

The issue only impacts Next Event Estimation. See images below.
The issue seems to be that within a region around a triangle, the correct (or close to correct) co-ordinate is sampled on the triangle. But outside that region, incorrect points are sampled on the triangle. I haven't looked into it to see if it's a UV sampling or geometry sampling issue.
The size of the region that renders correctly is determined by the size of the triangle. A larger triange has a larger area that renders correctly, while a smaller triangle has a smaller regeion that renders correctly.

Next Event Estimation Only	Forward Sampling Only

It seems like the issue was introduced with 38af5b0501005d8ee84a59f027417bf6a31fcc5e CC @brecht --- Just for reference, here's what I observed: 1. The issue only impacts Next Event Estimation. See images below. 2. The issue seems to be that within a region around a triangle, the correct (or close to correct) co-ordinate is sampled on the triangle. But outside that region, incorrect points are sampled on the triangle. I haven't looked into it to see if it's a UV sampling or geometry sampling issue. 3. The size of the region that renders correctly is determined by the size of the triangle. A larger triange has a larger area that renders correctly, while a smaller triangle has a smaller regeion that renders correctly. |Next Event Estimation Only|Forward Sampling Only| |-|-| |![NEE.jpg](/attachments/878f576c-3c8c-4c80-ac5b-e24f5bbe66e9)|![Forward.jpg](/attachments/48f7e335-de02-4376-ae26-a6f6d59d1b6f)|

NEE.jpg

29 KiB

Forward Path Tracing.jpg

30 KiB

Alaska referenced a pull request that will close this issue

2024-02-04 09:32:11 +01:00

Fix #117771: Incorrect Cycles light triangle sampling code #117801

Brecht Van Lommel referenced this issue from a commit

2024-02-05 13:56:28 +01:00

Fix #117771: Incorrect Cycles texture position on emissive triangles

Brecht Van Lommel closed this issue

2024-02-05 13:56:30 +01:00