Weld Modifier Proposal #70240

New Issue

Campbell Barton · 2019-09-25T14:50:23+02:00

Campbell Barton commented

2019-09-25 14:50:23 +02:00

Motivation

While modifiers such as spin, mirror & array can merge duplicates, there are times when
Some modifier setups don't can't as easily predict duplicate geometry.

Examples include:

Curve modifier deforming an object that loops back on it's self.
Bend modifier causing opposite edges touching when bending 360 degrees.
Beveled curves which taper to a point (although this could be supported without a modifier)

Lots of comments from users on
this thread .

Proposal

Seams: restrict welding to vertices along boundary edges.
Edge Collapse: collapse edges below the length threshold.
Vertex Group: option to limit welding to vertex groups.

There will be two methods available:

Simple (default)

This would be a fast weld operation that would support common welding operations - weld-seams/collapse-edges
although other cases could be supported in the future.

Merging geometry that would cause degenerate faces will be skipped
(this requires much more complex operation to properly handle).

(internally this will manipulate the Mesh structure without requiring it to be converted into BMesh).

Full

This would perform a full merge-by-distance,
with support for resolving degenerate cases, documented to be much slower
then the Simple operation.

(this can use the existing merge-by-distance code)

Pros

Fast by default, for merging boundaries of disconnected surfaces.
The ability only to merge a small subset of vertices should speed up the operation in most real world uses.

Cons

The Full merge-by-distance code uses a method that depends on vertex order

(picking all vertices closest to vertices at the start of the mesh). This means changing the vertex order of the input may cause the result
to *jitter*.

The Simple method will have limitations which might be hard to understand. Ideally we wouldn't have to select between two methods.

**Motivation** While modifiers such as spin, mirror & array can merge duplicates, there are times when Some modifier setups don't can't as easily predict duplicate geometry. Examples include: - Curve modifier deforming an object that loops back on it's self. - Bend modifier causing opposite edges touching when bending 360 degrees. - Beveled curves which taper to a point *(although this could be supported without a modifier)* Lots of comments from users on [this thread ](https://devtalk.blender.org/t/hurdles-to-implementing-merge-modifier/9718). **Proposal** - Seams: restrict welding to vertices along boundary edges. - Edge Collapse: collapse edges below the length threshold. - Vertex Group: option to limit welding to vertex groups. There will be two methods available: - **Simple** (default) ``` This would be a fast weld operation that would support common welding operations - weld-seams/collapse-edges although other cases could be supported in the future. ``` ``` Merging geometry that would cause degenerate faces will be skipped (this requires much more complex operation to properly handle). ``` *(internally this will manipulate the `Mesh` structure without requiring it to be converted into `BMesh`).* - **Full** ``` This would perform a full merge-by-distance, with support for resolving degenerate cases, documented to be much slower then the Simple operation. ``` *(this can use the existing merge-by-distance code)* ---- **Pros** - Fast by default, for merging boundaries of disconnected surfaces. - The ability only to merge a small subset of vertices should speed up the operation in most real world uses. **Cons** - The **Full** merge-by-distance code uses a method that depends on vertex order ``` (picking all vertices closest to vertices at the start of the mesh). This means changing the vertex order of the input may cause the result to *jitter*. ``` - The **Simple** method will have limitations which might be hard to understand. Ideally we wouldn't have to select between two methods.

Campbell Barton self-assigned this 2019-09-25 14:50:23 +02:00

Campbell Barton commented

2019-09-25 14:50:23 +02:00

Added subscriber: @ideasman42

Howard Trickey commented

2019-09-25 15:00:51 +02:00

Added subscriber: @howardt

Howard Trickey commented

2019-09-25 15:00:51 +02:00

Pointing out that some of the desire for this comes from the fact that the Bevel modifier can, as a result of clamping, put vertices on top of each other, and users would like them merged. As Campbell points out, the Bevel modifier itself could be changed to detect and merge in such cases. I would have done so if it were easy, but it is not so easy (the current code that merges nearby vertices gets quite complicated), so was delaying -- especially as my eventual goal is to get rid of clamping completely and continue beveling after such collisions cause merges.

All this is to say: restricting this to only happen at boundaries (seams) may not accomplish everything people want, so if possible that should be an option rather than a requirement,

Pointing out that some of the desire for this comes from the fact that the Bevel modifier can, as a result of clamping, put vertices on top of each other, and users would like them merged. As Campbell points out, the Bevel modifier itself could be changed to detect and merge in such cases. I would have done so if it were easy, but it is not so easy (the current code that merges nearby vertices gets quite complicated), so was delaying -- especially as my eventual goal is to get rid of clamping completely and continue beveling after such collisions cause merges. All this is to say: restricting this to only happen at boundaries (seams) may not accomplish everything people want, so if possible that should be an option rather than a requirement,

Dspazio commented

2019-09-25 15:03:04 +02:00

Added subscriber: @Dspazio

Campbell Barton commented

2019-09-25 15:03:18 +02:00

@howardt wouldn't collapsing edges handle this case?

We should be able to support this as long as it doesn't result in faces using the same edge/vertex twice.

@howardt wouldn't collapsing edges handle this case? We should be able to support this as long as it doesn't result in faces using the same edge/vertex twice.

Howard Trickey commented

2019-09-25 15:17:05 +02:00

Collapsing edges would mostly handle that case, yes. I wasn't sure whether you intended to support that everywhere or just as part of handling merges across boundaries, but thinking about it, you must have meant the former, because the latter wouldn't come up in most cases, if ever.

One case that your Simple solution would rule out: cases where bevel acts as an inset into a particular face (because all edges around that face are beveled). At some point, the inner face of the inset disappears (always, for triangles; for regular polygons otherwise). Users would probably like that face to go away and all the points of the inner face to weld together. And a variant on this: sometimes the inner face degenerates into a line (e.g., insetting a rectangle).

Collapsing edges would mostly handle that case, yes. I wasn't sure whether you intended to support that everywhere or just as part of handling merges across boundaries, but thinking about it, you must have meant the former, because the latter wouldn't come up in most cases, if ever. One case that your Simple solution would rule out: cases where bevel acts as an inset into a particular face (because all edges around that face are beveled). At some point, the inner face of the inset disappears (always, for triangles; for regular polygons otherwise). Users would probably like that face to go away and all the points of the inner face to weld together. And a variant on this: sometimes the inner face degenerates into a line (e.g., insetting a rectangle).

cédric lepiller commented

2019-09-25 15:21:13 +02:00

Added subscriber: @cedriclepiller

cédric lepiller commented

2019-09-25 15:21:13 +02:00

I can add some others examples we talked about in the Bevel modifier thread.

One more from fiendish55
https://i.imgur.com/PfjPJ8K.gifv

Maybe it could be possible with modifiers (bevel, merge, triangulate on ngons) to achieve this kind of non-destructive beveling.
c043c82a09.gif

I can add some others examples we talked about in the Bevel modifier thread. ![image.png](https://archive.blender.org/developer/F7774581/image.png) ![image.png](https://archive.blender.org/developer/F7774586/image.png) ![image.png](https://archive.blender.org/developer/F7774589/image.png) One more from fiendish55 https://i.imgur.com/PfjPJ8K.gifv Maybe it could be possible with modifiers (bevel, merge, triangulate on ngons) to achieve this kind of non-destructive beveling. https://devtalk.blender.org/uploads/default/original/1X/c043c82a09a5ea04bc1b1bd4c8962e9f2d9b3d72.gif

Bruno Ducloy commented

2019-09-25 15:50:33 +02:00

Added subscriber: @Helo

Oliver Milas commented

2019-09-25 15:50:56 +02:00

Added subscriber: @Spatz

Matt Heimlich commented

2019-09-25 22:22:39 +02:00

Added subscriber: @MatthewHeimlich

Matt Heimlich commented

2019-09-25 22:22:39 +02:00

Please keep things like multires in mind during the design process. One of the best use cases that I can imagine for this kind of modifier is for sculptors who wish to split objects that should visibly be contiguous into multiple pieces so that they can really crank up the level of subdivision on each individual part for multires sculpting while still having them act like a single mesh for animation, edit mode, etc.

Joseph Brandenburg commented

2019-09-26 01:12:04 +02:00

Added subscriber: @Josephbburg

Joseph Brandenburg commented

2019-09-26 01:12:04 +02:00

I'm curious if this is planned to support joining objects, or only work on a single object? Sometimes in animation it would be nice to merge edges of objects together (hand/sleeve for example).

0rAngE commented

2019-09-26 03:55:12 +02:00

Added subscriber: @0rAngE

Campbell Barton commented

2019-09-26 04:49:37 +02:00

@Josephbburg it's possible although it wouldn't be a target for the first version of this patch.

Also, this feature seems better suited to a grouping than a single objects modifier - where all objects in the group have their seams welded.

@Josephbburg it's possible although it wouldn't be a target for the first version of this patch. Also, this feature seems better suited to a grouping than a single objects modifier - where all objects in the group have their seams welded.

Erick Tukuniata commented

2019-09-26 09:10:30 +02:00

Added subscriber: @ErickNyanduKabongo

Erick Tukuniata commented

2019-09-26 09:10:30 +02:00

In #70240#783915, @MatthewHeimlich wrote:
Please keep things like multires in mind during the design process. One of the best use cases that I can imagine for this kind of modifier is for sculptors who wish to split objects that should visibly be contiguous into multiple pieces so that they can really crank up the level of subdivision on each individual part for multires sculpting while still having them act like a single mesh for animation, edit mode, etc.

I second this, If you guys can make it work, we will have a very powerful multires.

> In #70240#783915, @MatthewHeimlich wrote: > Please keep things like multires in mind during the design process. One of the best use cases that I can imagine for this kind of modifier is for sculptors who wish to split objects that should visibly be contiguous into multiple pieces so that they can really crank up the level of subdivision on each individual part for multires sculpting while still having them act like a single mesh for animation, edit mode, etc. I second this, If you guys can make it work, we will have a very powerful multires.

Ariel Tavori commented

2019-09-26 21:24:51 +02:00

Added subscriber: @Ariel-Tavori

Tosky commented

2019-09-29 18:04:56 +02:00

Added subscriber: @Tosky

Tosky commented

2019-09-29 18:04:56 +02:00

The "full method" use the existing merge-by-distance code; it's right to say that will give us options like 'merge at first/last/3dcursor' and peraphs Empty? Because that could open new scenarios.

Campbell Barton commented

2019-09-30 10:42:20 +02:00

@Tosky, these don't make sense for modifiers since defining operations on individual vertices doesn't fit well with the current modifier stack.

Bartosz Moniewski commented

2019-10-10 13:27:30 +02:00

Added subscriber: @BartekMoniewski

Andrei Nadin commented

2019-10-14 11:17:04 +02:00

Added subscriber: @AnadinX

Darrell James commented

2019-10-14 14:27:12 +02:00

Added subscriber: @darrelljuk

ML commented

2019-10-14 21:15:02 +02:00

Added subscriber: @MarcelLegindi

cédric lepiller commented

2019-10-29 12:08:36 +01:00

Hi,
Any update about this modifier for 2.82?

Hi, Any update about this modifier for 2.82?

Campbell Barton commented

2019-10-31 16:42:10 +01:00

@cedriclepiller after 2.81 release.

cédric lepiller commented

2019-11-01 09:53:43 +01:00

Ok, thank you for your answer ;)

Julien Leménicier commented

2019-11-05 20:13:03 +01:00

Added subscriber: @lemenicier_julien

item412 commented

2019-11-26 00:39:55 +01:00

Added subscriber: @item412

LapisSea commented

2019-11-26 02:37:35 +01:00

Added subscriber: @LapisSea

dupoxy commented

2019-11-29 17:14:41 +01:00

Added subscriber: @dupoxy

Francois Rimasson commented

2019-12-05 19:33:07 +01:00

Added subscriber: @FrancoisRimasson

Francois Rimasson commented

2019-12-05 19:38:22 +01:00

I wish to be able to collapse edge with no faces around (ie : edges used for sewing garments in the cloth modifier)

I wish to be able to collapse edge with no faces around (ie : edges used for sewing garments in the cloth modifier) ![image.png](https://archive.blender.org/developer/F8191971/image.png)

Brecht Van Lommel commented

2020-01-15 15:22:45 +01:00

Added subscribers: @mano-wii, @brecht

Brecht Van Lommel commented

2020-01-15 15:22:45 +01:00

@mano-wii, can you close this task and create a follow-up task for remaining improvements to the weld modifier, so we can consider this one finished for the release?

If there are still things to improve for 2.82, please create another task for that and tag it with the Blender 2.82 milestone.

@mano-wii, can you close this task and create a follow-up task for remaining improvements to the weld modifier, so we can consider this one finished for the release? If there are still things to improve for 2.82, please create another task for that and tag it with the Blender 2.82 milestone.

Germano Cavalcante commented

2020-01-15 15:49:10 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Germano Cavalcante closed this issue

2020-01-15 15:49:10 +01:00

Germano Cavalcante commented

2020-01-15 15:49:10 +01:00

As the main goal of this task (Weld Modifier Implementation) has already been resolved, closing.
Remaining proposals moved to #73139 (Weld Modifier Improvements).

As the main goal of this task (Weld Modifier Implementation) has already been resolved, closing. Remaining proposals moved to #73139 (Weld Modifier Improvements).

Thomas Dinges added this to the 2.82 milestone 2023-02-08 16:41:47 +01:00

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Weld Modifier Proposal #70240