Microdisplacement; stitching between two faces of different material indices does not exist (when dicing is used) #49049

Closed
opened 2016-08-08 20:57:34 +02:00 by Adam Friesen · 12 comments

System Information
Win10 64 bit; 24 gigs RAM; third-gen i7 CPU; ATI 79xx GPU

Blender Version
Broken: hash a0c1876
Worked: never

Short description of error
When you enable the rendertime dicing in the subsurf modifier (for displacement) and the mesh has more than one material index, both the rendered view and F12 render will reveal that the faces are not connected in any way (but displacement without the dicing works as it should

Exact steps for others to reproduce the error
Open the .blend file and switch to the rendered view (or press F12)

image
Microdisp_bug2.jpg

blend
MicroDispBug2.blend

I'm not entirely sure if you're accepting bug reports for this feature yet, but then again there's no user-visible list of remaining todo items so as to know whether to report something.

**System Information** Win10 64 bit; 24 gigs RAM; third-gen i7 CPU; ATI 79xx GPU **Blender Version** Broken: hash a0c1876 Worked: never **Short description of error** When you enable the rendertime dicing in the subsurf modifier (for displacement) and the mesh has more than one material index, both the rendered view and F12 render will reveal that the faces are not connected in any way (but displacement without the dicing works as it should **Exact steps for others to reproduce the error** Open the .blend file and switch to the rendered view (or press F12) **image** ![Microdisp_bug2.jpg](https://archive.blender.org/developer/F334370/Microdisp_bug2.jpg) **blend** [MicroDispBug2.blend](https://archive.blender.org/developer/F334369/MicroDispBug2.blend) I'm not entirely sure if you're accepting bug reports for this feature yet, but then again there's no user-visible list of remaining todo items so as to know whether to report something.
Author

Changed status to: 'Open'

Changed status to: 'Open'
Author

Added subscriber: @Ace_Dragon

Added subscriber: @Ace_Dragon

#49967 was marked as duplicate of this issue

#49967 was marked as duplicate of this issue
Adam Friesen changed title from Ex. Microdisplacement; stitching between two faces of different material indices does not exist (when dicing is used) to Exp. Microdisplacement; stitching between two faces of different material indices does not exist (when dicing is used) 2016-08-08 20:58:21 +02:00
Mai Lavelle self-assigned this 2016-08-08 22:28:06 +02:00
Member

I'm not sure this is a bug but rather a limitation. By using two materials with different displacement settings you've created a discontinuous function; the surface literally doesn't exist for those points.

If you have a specific idea on how you expect this to be resolved could you please describe what you expect to happen?

I'm not sure this is a bug but rather a limitation. By using two materials with different displacement settings you've created a discontinuous function; the surface literally doesn't exist for those points. If you have a specific idea on how you expect this to be resolved could you please describe what you expect to happen?
Author

The expected result would be something like this
Microdisp_bug2B.jpg

The edges of the red zone is not the prettiest thing, but the mesh at least is a closed volume (this is how discontinuous values have traditionally been handled in 3D).

Now I'm not sure if OpenSubDiv here has the ability to produce such a result in this case, if it's an OSD limitation then there's not much that can be done until Pixar and co. decide to resolve it.

The expected result would be something like this ![Microdisp_bug2B.jpg](https://archive.blender.org/developer/F334411/Microdisp_bug2B.jpg) The edges of the red zone is not the prettiest thing, but the mesh at least is a closed volume (this is how discontinuous values have traditionally been handled in 3D). Now I'm not sure if OpenSubDiv here has the ability to produce such a result in this case, if it's an OSD limitation then there's not much that can be done until Pixar and co. decide to resolve it.
Member

Added subscriber: @brecht

Added subscriber: @brecht
Member

Nothing to do with OSD

While I can understand the want of a closed mesh I'm still not convinced that this is the correct behavior, in fact I feel like the case of the surface being stitched together when adaptive subdivision isn't in use is wrong...

You'll notice that the stitched part in your image is red, but what if the artist had wanted it to be white? The choice is arbitrary, and there's no way to allow control over what happens. Also the quality of the polygons in the stitched area will degrade quite quickly as the intensity of displacement increases. Finally, I cant really think of a case where this kind of mixing displacement shaders on a single mesh would be necessary in an actual scene. For those reasons I think we should leave the current behavior as is and have non-adaptive meshes match.

@brecht, do you have an opinion on what correct behavior should be here?

Nothing to do with OSD While I can understand the want of a closed mesh I'm still not convinced that this is the correct behavior, in fact I feel like the case of the surface being stitched together when adaptive subdivision isn't in use is wrong... You'll notice that the stitched part in your image is red, but what if the artist had wanted it to be white? The choice is arbitrary, and there's no way to allow control over what happens. Also the quality of the polygons in the stitched area will degrade quite quickly as the intensity of displacement increases. Finally, I cant really think of a case where this kind of mixing displacement shaders on a single mesh would be necessary in an actual scene. For those reasons I think we should leave the current behavior as is and have non-adaptive meshes match. @brecht, do you have an opinion on what correct behavior should be here?

If you want to actually break up the mesh or create discontinuities that seems more the task of modifiers or modelling tools.

If possible I'd suggest to average the vertex locations from both sides. Mainly for the case where the user intended to create a smooth transition but precision issues or a small mismatch causes the mesh to not be entirely watertight.

I imagine doing stitching is problematic for the geometry cache, though if we want to ensure watertight results it might be inevitable to look across the edges even with a single material?

Either way I would consider this pretty low priority, displacement with a discontinuous texture is also problematic in general.

If you want to actually break up the mesh or create discontinuities that seems more the task of modifiers or modelling tools. If possible I'd suggest to average the vertex locations from both sides. Mainly for the case where the user intended to create a smooth transition but precision issues or a small mismatch causes the mesh to not be entirely watertight. I imagine doing stitching is problematic for the geometry cache, though if we want to ensure watertight results it might be inevitable to look across the edges even with a single material? Either way I would consider this pretty low priority, displacement with a discontinuous texture is also problematic in general.
Brecht Van Lommel changed title from Exp. Microdisplacement; stitching between two faces of different material indices does not exist (when dicing is used) to Microdisplacement; stitching between two faces of different material indices does not exist (when dicing is used) 2016-08-24 20:34:43 +02:00

Marking this as a To Do item since this will still be an experimental feature in 2.78.

Marking this as a To Do item since this will still be an experimental feature in 2.78.
Member

Added subscribers: @ErickNyanduKabongo, @MaiLavelle

Added subscribers: @ErickNyanduKabongo, @MaiLavelle
Mai Lavelle was unassigned by Brecht Van Lommel 2018-01-25 08:35:04 +01:00
Member

Changed status from 'Open' to: 'Resolved'

Changed status from 'Open' to: 'Resolved'
Mai Lavelle self-assigned this 2019-08-27 20:31:11 +02:00
Member

Fixed by 697fd8650

Fixed by 697fd8650
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
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
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#49049
No description provided.