Adding very weak emissions to the scene weakens the highlights in cycles render #73328
Labels
No Label
Interest
Alembic
Interest
Animation & Rigging
Interest
Asset Browser
Interest
Asset Browser Project Overview
Interest
Audio
Interest
Automated Testing
Interest
Blender Asset Bundle
Interest
BlendFile
Interest
Collada
Interest
Compatibility
Interest
Compositing
Interest
Core
Interest
Cycles
Interest
Dependency Graph
Interest
Development Management
Interest
EEVEE
Interest
EEVEE & Viewport
Interest
Freestyle
Interest
Geometry Nodes
Interest
Grease Pencil
Interest
ID Management
Interest
Images & Movies
Interest
Import Export
Interest
Line Art
Interest
Masking
Interest
Metal
Interest
Modeling
Interest
Modifiers
Interest
Motion Tracking
Interest
Nodes & Physics
Interest
OpenGL
Interest
Overlay
Interest
Overrides
Interest
Performance
Interest
Physics
Interest
Pipeline, Assets & IO
Interest
Platforms, Builds & Tests
Interest
Python API
Interest
Render & Cycles
Interest
Render Pipeline
Interest
Sculpt, Paint & Texture
Interest
Text Editor
Interest
Translations
Interest
Triaging
Interest
Undo
Interest
USD
Interest
User Interface
Interest
UV Editing
Interest
VFX & Video
Interest
Video Sequencer
Interest
Virtual Reality
Interest
Vulkan
Interest
Wayland
Interest
Workbench
Interest: X11
Legacy
Blender 2.8 Project
Legacy
Milestone 1: Basic, Local Asset Browser
Legacy
OpenGL Error
Meta
Good First Issue
Meta
Papercut
Meta
Retrospective
Meta
Security
Module
Animation & Rigging
Module
Core
Module
Development Management
Module
EEVEE & Viewport
Module
Grease Pencil
Module
Modeling
Module
Nodes & Physics
Module
Pipeline, Assets & IO
Module
Platforms, Builds & Tests
Module
Python API
Module
Render & Cycles
Module
Sculpt, Paint & Texture
Module
Triaging
Module
User Interface
Module
VFX & Video
Platform
FreeBSD
Platform
Linux
Platform
macOS
Platform
Windows
Priority
High
Priority
Low
Priority
Normal
Priority
Unbreak Now!
Status
Archived
Status
Confirmed
Status
Duplicate
Status
Needs Info from Developers
Status
Needs Information from User
Status
Needs Triage
Status
Resolved
Type
Bug
Type
Design
Type
Known Issue
Type
Patch
Type
Report
Type
To Do
No Milestone
No project
No Assignees
5 Participants
Notifications
Due Date
No due date set.
Dependencies
No dependencies set.
Reference: blender/blender#73328
Loading…
Reference in New Issue
No description provided.
Delete Branch "%!s(<nil>)"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
System Information
Operating system:macOS 10.15.2
Graphics card:Radeon Pro 580X 8 GB
Blender Version
Broken:2.82 Beta 2020-01-22 12:36 Hash:a60a623a1ac5
Worked: (optional)
Short description of error
Adding very weak emissions to the scene weakens the highlights in cycles render
Exact steps for others to reproduce the error
Light_test.mp4
Uploaded blend file has strong emission, very weak emission and background light.
Very weak emissions have keyframes, 1 frame has a value of 0, and 2 frame have a value of 0.001.
Comparing the rendered images shows that the highlights of the 2 frame is weaker than the highlights of the 1 frame.
It seems strange that the highlights get weaker if you add a very weak emission that does not affect the scene.
Not included in the video, but placing very weak emissions close to strong emissions has the same effect.
If you add weak radiation, I think it will be a bit brighter, but the result will be darker.
Light_test.blend
Added subscriber: @cubimation
Added subscriber: @MarcinTwarowski
It would be easier to test it if you simplified that scene. There are 88 thousand objects. I tried to delete the layer with those cubes but it takes Blender forever.
I upload a light sized file
Light_test2.blend
Added subscriber: @mano-wii
Changed status from 'Needs Triage' to: 'Confirmed'
I can confirm.
Operating system: Windows-10-10.0.18941 64 Bits
Graphics card: Radeon (TM) RX 480 Graphics ATI Technologies Inc. 4.5.13559 Core Profile Context 26.20.12028.2
The problem is seen in both GPU and CPU
Added subscriber: @EAW
I don't think that this is a bug, but a known limitation of Monte Carlo ray tracing.
Cycles has 2 sampling methods.
You have a light with a strength of 678.4, the world background at 1, and then you add a light with a strength of 0.001. Frame 1: Ever pixel sample is either lit by the 678.4 light or the world background at 1, chosen at random. Frame 2: you add in another light source at 0.001. The result is that it will bring the overall lighting intensity down, because it is using up the random samples that would have gone to the other light sources.
If you switch to Branched Path Tracing, which takes all lights into account, you will see that the additional light makes the scene brighter.
Emissive materials have Multiple Importance Sampling on by default.
Turn off Multiple Importance Sampling for the 0.001 light, even when using Path Tracing, and Frame 1 & 2 are identical, as the 0.001 light is too minuscule to contribute any change.
Added subscriber: @brecht
Added subscriber: @Alaska
This appears to be the same issue as #97305 (As light object numbers increase, the indirect brightness of bright lights is decreased while indirect light clamping enabled - Cycles). I will merge these reports.
Closed as duplicate of #97305