Nodes Don't Register Alpha Channel #32580

Closed
opened 2012-09-19 05:39:49 +02:00 by David Brennan · 7 comments

%%%In the Node Editor, there are certain Nodes which do not transfer the alpha data. This effectively prevents you then from using further Nodes beyond them (or makes it very difficult).

For example, if you have Text on one Render Layer and then a regular scene on another Render Layer, and you want the Text to have a black outline, so you set up a "Dilate/Erode" Node beneath....that Node won't register any alpha data, and so you won't be able to overlay it!

I've seen this in MANY Nodes. Attached is a .Blend with a simple scene and just two of the problem Nodes: Lens Distort and Dilate/Erode. This will allow you to quickly confirm the problem. A screencap is also attached.

(In the interim, if there is anybody who can offer any work-arounds, that would be fantastic.)

Blender 2.63a
Windows XP 32-bit%%%

%%%In the Node Editor, there are certain Nodes which do not transfer the alpha data. This effectively prevents you then from using further Nodes beyond them (or makes it very difficult). For example, if you have Text on one Render Layer and then a regular scene on another Render Layer, and you want the Text to have a black outline, so you set up a "Dilate/Erode" Node beneath....that Node won't register any alpha data, and so you won't be able to overlay it! I've seen this in MANY Nodes. Attached is a .Blend with a simple scene and just two of the problem Nodes: Lens Distort and Dilate/Erode. This will allow you to quickly confirm the problem. A screencap is also attached. (In the interim, if there is anybody who can offer any work-arounds, that would be fantastic.) Blender 2.63a Windows XP 32-bit%%%
Author

Changed status to: 'Open'

Changed status to: 'Open'
Author

%%%(This should be in the compositor category, obviously. Sorry that I forgot to specify that originally.)%%%

%%%(This should be in the compositor category, obviously. Sorry that I forgot to specify that originally.)%%%

%%%This appears to work

http://getblended.org/screens/setalpha.jpg%%%

%%%This appears to work http://getblended.org/screens/setalpha.jpg%%%
Author

%%%That looks like a great work-around, although hopefully the Bug will be fixed so this won't be necessary and other users won't get aggravated.

Alternately, "JaceP" had a set-up in which you use a pair of "Separate RGBA" Nodes to isolate the colors from the alpha channel originally, but this work-around definitely seems leaner and faster. Thanks!

(I can't escape from your good works, Olson!)%%%

%%%That looks like a great work-around, although hopefully the Bug will be fixed so this won't be necessary and other users won't get aggravated. Alternately, "JaceP" had a set-up in which you use a pair of "Separate RGBA" Nodes to isolate the colors from the alpha channel originally, but this work-around definitely seems leaner and faster. Thanks! (I can't escape from your good works, Olson!)%%%

%%%Indeed some nodes are not dealing with alpha as it could be expected. In most cases it's because alpha is not a part of equotion and it's not so obvious which value it should be. Foe\r sure some nodes could be improved to give reasonable alpha, but it's not considered a bug.

Also, value nodes (dilate/erode i.e.) are working on a single channel only. It's how they're designed to work and they can not deal with alpha.

Added notes to http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#Compositing

Thanks for the report, but marking as a TODO now.%%%

%%%Indeed some nodes are not dealing with alpha as it could be expected. In most cases it's because alpha is not a part of equotion and it's not so obvious which value it should be. Foe\r sure some nodes could be improved to give reasonable alpha, but it's not considered a bug. Also, value nodes (dilate/erode i.e.) are working on a single channel only. It's how they're designed to work and they can not deal with alpha. Added notes to http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#Compositing Thanks for the report, but marking as a TODO now.%%%

Changed status from 'Open' to: 'Archived'

Changed status from 'Open' to: 'Archived'
Author

%%%Thank you for the information and for considering this so deeply, Sergey. Hopefully, even though this doesn't quite qualify as a "bug", some productive Blender master will be able to amend and refine how some of these Nodes utilize the alpha channel.%%%

%%%Thank you for the information and for considering this so deeply, Sergey. Hopefully, even though this doesn't quite qualify as a "bug", some productive Blender master will be able to amend and refine how some of these Nodes utilize the alpha channel.%%%
Sign in to join this conversation.
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
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
3 Participants
Notifications
Due Date
The due date is invalid or out of range. Please use the format 'yyyy-mm-dd'.

No due date set.

Dependencies

No dependencies set.

Reference: blender/blender#32580
No description provided.