Cycles refraction seems wrong compared to BI or Vray #39761
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
4 Participants
Notifications
Due Date
No due date set.
Dependencies
No dependencies set.
Reference: blender/blender#39761
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 and graphics card
Win 7 64 bits, gforce 770
Blender Version
Broken: (example: 2.69.7
4b206af
, see splash screen)Worked: (optional)
official 2.70 and last nightly blender-2.70-b179647-win64
Short description of error
When I render glass with cycles, result seems wrong. Refraction seems to lack of detail, compared to Vray, Yafaray or even Blender internal... So I made a test file with a pure refraction shader and I can confirm this. As if refraction bounces was kind of limited (my test was in full illumination mode)
By the way, I've got another little issue with cycles with CPU in viewport. Some part of refractive objects are black, if you choose GPU, it's right, or if you laucn a real render, but CPU in viewport does strange things. Maybe this is correlated.
Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps
hit render
cycles.blend
BI.blend
Changed status to: 'Open'
Added subscriber: @sarazinjean-francois
Forgotten to say : images in order are from : Cycles - Vray and BI. All material are pure refraction with an ior of 1.5. Just one light, no shadow.
Added subscriber: @mont29
It looks ok to me, but see the description here, a refraction BSDF by itself is not so useful.
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/Shaders#Refraction
You probably want to use the Glass BSDF to get something comparable, a lot of the detail comes from the interaction between refraction and reflection. Also note that the number of glossy and transmission bounces in the light paths panel influences the result.
As for CPU and GPU differences, for me the render results look basically the same with this file.
you're right, with a glass shader it works. This is strange, I thought Blender Internal, or Vray, compute no reflections in its refraction, when reflection are disabled or completly dark. Anyway, no I know I shouldn't use refraction alone. And for the CPU/GPU issue it only happens in viewport, not in render, and only with refraction shader.
Added subscriber: @gandalf3
Here's a comparison of CPU and GPU (GTX 460) in the viewport (using the attached file):
GPU
CPU
The final render looks like the GPU.