Add Precise Seam placement feature #134

New Issue

MrUnknownDE · 2026-04-05T16:18:35+02:00

MrUnknownDE commented

2026-04-05 16:18:35 +02:00

Originally created by @DImagine on 3/26/2026

New modifier type Precise Seam that allows users to control exact seam placement on 3D prints using volume-based intersection geometry.

Includes:

6 seam modifier subtypes: Center, Left, Right, Enforced, Blocked, Neutral
Core algorithm: perimeter segment detection via mesh-layer intersection
SeamPlacer integration: modifiers override seam zone painting on affected perimeters
GUI: context menus, icons, volume sorting, Change Type support

Description

Precise Seam is a modifier system that gives you precise control over where exactly the seam will be placed on a model during 3D printing. You place a modifier volume on the model, and the seam runs exactly where that volume intersects the model's walls.

The system allows you to either define the exact seam position on the perimeter, or set up allowed and forbidden zones.

For quick results, you can use built-in primitives as modifiers. For complex geometries, you can create a custom auxiliary body once in any 3D modeling software and reuse it permanently. Even for the most complex geometries, placing the seam takes just a couple of clicks. This is especially valuable during iterative design — since the modifier is a persistent object, it survives model changes automatically. There is no need to repaint seam zones after each revision. This completely eliminates manual work and provides an unprecedented level of convenience for seam control.

https://github.com/user-attachments/assets/132c1d7b-db29-430f-8adb-6a46be05e3d1

Note

This modifier body was created by sweeping a triangular cross-section along a curved path on the surface of the mesh. A circle is easier to use as the base profile, but a regular polygon (with enough sides) works faster — it has a predictable edge count, while a circle tends to be unnecessarily over-detailed.

Modifier Types

Precise Seam includes 6 modifier types, divided into two groups:

Strong Modifiers (Exact Positioning)

Define a specific point on the perimeter where the seam will be placed. They work strictly: if a Strong modifier intersects a wall — the seam goes exactly there, no alignment strategy can move it.

Type	Behavior	When to Use
Center	Seam is placed at the geometric center of the intersection segment between the modifier and the wall	Universal option. The seam will be in the middle of the intersection area — the most predictable behavior
Left	Seam is placed at the beginning (first point) of the intersection segment	When you need to pin the seam to a specific edge of the intersection
Right	Seam is placed at the end (last point) of the intersection segment	When you need to pin the seam to the opposite edge of the intersection

Weak Modifiers (Zone-Based Control)

Do not define a specific point, but mark zones on the perimeter, influencing the priority during seam selection by the standard algorithm.

Type	Behavior	When to Use
Enforced	The intersection zone is marked as preferred (green) for the seam	Equivalent to manually painting green seam zones. Use when you want to softly attract the seam to an area without pinning it to a specific point
Blocked	The intersection zone is marked as forbidden (red) for the seam	Equivalent to manually painting red seam zones. Use when you need to remove the seam from a visible surface or critical area
Neutral	The intersection zone is marked as neutral (gray)	Use when you want to reset a zone to the initial neutral state

Warning

The modifier must penetrate the object deep enough to account for the seam width, since the algorithm intersects the printed perimeter, which is offset inward from the wall by half the seam width.

Warning

Strong modifiers (Center/Left/Right): only one intersection per perimeter is supported, since there can be only one seam. Additional intersections are ignored.

Weak modifiers (Enforced/Blocked/Neutral): multiple intersections are supported, but none of them should pass through the model entirely. A through-body intersection produces multiple segments, of which only one will be processed.

In both cases, a pop-up warning is shown when unsupported intersections are detected.

If any modifier has a multiply-connected cross-section (e.g. a hollow shape), it is skipped and a corresponding notification is shown.

Full containment of the perimeter within modifier is not handled.

Modifier Behavior and Technical Notes

Precise Seam modifiers integrate smoothly into the existing seam placement pipeline. In areas not covered by any modifier, the built-in seam algorithms work unchanged.

The modifiers simply augment (with higher priority) the existing zone-painting mechanism:

Strong modifiers: mark all perimeter points as BLOCKED except for one, which is marked ENFORCED. The built-in algorithms then take over from there.
Weak modifiers: apply automatic zone painting on top of any manual painting, marking points according to their type (Enforced/Blocked/Neutral).

Hierarchy and Priorities

When multiple modifiers are present, their priority is determined by position in the object tree — modifiers higher in the tree have higher priority. Strong modifiers are always positioned above Weak ones in the tree — this is built-in behavior, because Strong always takes precedence over Weak. When a Strong modifier fires, all modifiers below it in the list are ignored for that perimeter.

If multiple Weak modifiers overlap in the same zone, the ones higher in the list take precedence, and the zone is painted in the corresponding "colors" according to this order.

Modifier order can be rearranged via drag & drop in the object tree.

Working in the Interface

Adding a Precise Seam Modifier

Adding a Precise Seam modifier follows the standard modifier workflow: right-click on an object — either in the object tree or on a selected object in the scene — and select "Add precise seam" from the context menu, then choose a specific 3D shape for the modifier.

You can also convert any existing 3D object (including other modifiers) in the scene into a Precise Seam modifier. The only requirement is that only objects within a group containing at least one other body can be converted into modifiers — a standalone object outside of any group cannot be converted. Groups and hierarchy are visible in the object tree.

To convert, find the object you want to convert in the object tree and make sure it is within a group. Select it and verify visually in the scene that it is the correct object. Then right-click it (in the scene or in the tree), select "Change type" from the context menu, and choose "Precise Seam" from the dropdown list.

https://github.com/user-attachments/assets/b29c87ea-adce-445c-b5ba-145f90e792c2

Changing the Modifier Type

Once you have a Precise Seam modifier, you can change its type to any of the six available variants. Select the modifier in the tree or in the scene, right-click, and choose "Precise Seam Type" from the context menu — it will show a list of all Precise Seam modifier types. Select the one you need.

Visual Distinction of Types

Each Precise Seam type has its own color in the 3D view (all at 60% transparency):

Type	Color	Description
Center	🟠 Orange	Warm orange — primary Strong type
Left	🟡 Gold	Bright golden
Right	🟠 Dark Orange	Deep orange
Enforced	🟢 Green	Green — "allowed" zone
Blocked	🔴 Red	Red — "forbidden" zone
Neutral	⚪ Gray	Gray — neutral zone

Strong modifiers are visually unified with warm orange tones. Weak modifiers use intuitive colors: green = allowed, red = forbidden, gray = neutral.

YouTube Full Demo Video

Demonstrates the behavior of all six modifier subtypes and their application hierarchy based on their position in the object tree.

Test Files

Test Bell Object.zip This test file was created by drawing a spline curve on the surface of the printed object, then sweeping a triangular profile along it (Swept Boss/Base in SolidWorks). This way the seam follows the desired trajectory precisely. A circular profile can also be used as the sweep cross-section — this avoids orientation issues.

Big Test.zip Another file demonstrating all modifier types.

Note

These test files have only been verified on Windows. Testing on Linux (AppImage/Flatpak) and macOS would be greatly appreciated — please share your results in the comments.

Debug Instruments

A debug branch that dumps geometry data to files:
https://github.com/DImagine/OrcaSlicer/tree/feature-precise-seam-debug

Python scripts for data visualization:
Precise Seam Python Visual Debug.zip

Feature Development Progress Log

Claude Code and Codex were actively used during feature development. Progress data was saved at each stage. This information is included for reference, as it may be helpful for understanding the algorithm's internals.
Precise Seam Progress Log.zip

Closes #11162

Changelog

2026-03-27: Added handling for multiple intersection edge case
2026-03-28: Added pop-up warning message if multiple intersections are detected
2026-03-28: Improved detection and handling of multiple intersections, refined user notifications for problematic modifiers
2026-03-29: Some minor updates and improvements
2026-03-31: Refactor PreciseSeam based on AI code review findings

*Originally created by @DImagine on 3/26/2026* New modifier type **Precise Seam** that allows users to control exact seam placement on 3D prints using volume-based intersection geometry. Includes: - 6 seam modifier subtypes: Center, Left, Right, Enforced, Blocked, Neutral - Core algorithm: perimeter segment detection via mesh-layer intersection - SeamPlacer integration: modifiers override seam zone painting on affected perimeters - GUI: context menus, icons, volume sorting, Change Type support # Description **Precise Seam** is a modifier system that gives you precise control over where exactly the seam will be placed on a model during 3D printing. You place a modifier volume on the model, and the seam runs exactly where that volume intersects the model's walls. The system allows you to either define the exact seam position on the perimeter, or set up allowed and forbidden zones. For quick results, you can use built-in primitives as modifiers. For complex geometries, you can create a custom auxiliary body once in any 3D modeling software and reuse it permanently. Even for the most complex geometries, placing the seam takes just a couple of clicks. This is especially valuable during **iterative design** — since the modifier is a persistent object, it survives model changes automatically. There is no need to repaint seam zones after each revision. This completely eliminates manual work and provides an unprecedented level of convenience for seam control. https://github.com/user-attachments/assets/132c1d7b-db29-430f-8adb-6a46be05e3d1 > [!NOTE] > This modifier body was created by sweeping a triangular cross-section along a curved path on the surface of the mesh. A circle is easier to use as the base profile, but a **regular polygon** (with enough sides) works faster — it has a predictable edge count, while a circle tends to be unnecessarily over-detailed. --- ## Modifier Types Precise Seam includes **6 modifier types**, divided into two groups: ### Strong Modifiers (Exact Positioning) Define a **specific point** on the perimeter where the seam will be placed. They work strictly: if a Strong modifier intersects a wall — the seam goes exactly there, no alignment strategy can move it. | Type | Behavior | When to Use | |------|----------|-------------| | **Center** | Seam is placed at the **geometric center** of the intersection segment between the modifier and the wall | Universal option. The seam will be in the middle of the intersection area — the most predictable behavior | | **Left** | Seam is placed at the **beginning** (first point) of the intersection segment | When you need to pin the seam to a specific edge of the intersection | | **Right** | Seam is placed at the **end** (last point) of the intersection segment | When you need to pin the seam to the opposite edge of the intersection | ### Weak Modifiers (Zone-Based Control) Do not define a specific point, but **mark zones** on the perimeter, influencing the priority during seam selection by the standard algorithm. | Type | Behavior | When to Use | |------|----------|-------------| | **Enforced** | The intersection zone is marked as **preferred** (green) for the seam | Equivalent to manually painting green seam zones. Use when you want to softly attract the seam to an area without pinning it to a specific point | | **Blocked** | The intersection zone is marked as **forbidden** (red) for the seam | Equivalent to manually painting red seam zones. Use when you need to remove the seam from a visible surface or critical area | | **Neutral** | The intersection zone is marked as **neutral** (gray) | Use when you want to reset a zone to the initial neutral state | > [!WARNING] > The modifier must penetrate the object deep enough to account for the seam width, since the algorithm intersects the printed perimeter, which is offset inward from the wall by half the seam width. > [!WARNING] > Strong modifiers (Center/Left/Right): only one intersection per perimeter is supported, since there can be only one seam. Additional intersections are ignored. > > Weak modifiers (Enforced/Blocked/Neutral): multiple intersections are supported, but none of them should pass through the model entirely. A through-body intersection produces multiple segments, of which only one will be processed. > > In both cases, a pop-up warning is shown when unsupported intersections are detected. > >If any modifier has a multiply-connected cross-section (e.g. a hollow shape), it is skipped and a corresponding notification is shown. > > Full containment of the perimeter within modifier is not handled. > --- ## Modifier Behavior and Technical Notes Precise Seam modifiers integrate smoothly into the existing seam placement pipeline. In areas not covered by any modifier, the built-in seam algorithms work unchanged. The modifiers simply augment (with higher priority) the existing zone-painting mechanism: - **Strong modifiers**: mark all perimeter points as BLOCKED except for one, which is marked ENFORCED. The built-in algorithms then take over from there. - **Weak modifiers**: apply automatic zone painting on top of any manual painting, marking points according to their type (Enforced/Blocked/Neutral). --- ## Hierarchy and Priorities When multiple modifiers are present, their priority is determined by position in the object tree — modifiers higher in the tree have higher priority. Strong modifiers are always positioned above Weak ones in the tree — this is built-in behavior, because Strong always takes precedence over Weak. When a Strong modifier fires, all modifiers below it in the list are ignored for that perimeter. If multiple Weak modifiers overlap in the same zone, the ones higher in the list take precedence, and the zone is painted in the corresponding "colors" according to this order. Modifier order can be rearranged via **drag & drop** in the object tree. --- ## Working in the Interface ### Adding a Precise Seam Modifier Adding a Precise Seam modifier follows the standard modifier workflow: right-click on an object — either in the object tree or on a selected object in the scene — and select **"Add precise seam"** from the context menu, then choose a specific 3D shape for the modifier. You can also convert any existing 3D object (including other modifiers) in the scene into a Precise Seam modifier. The only requirement is that only objects within a group containing at least one other body can be converted into modifiers — a standalone object outside of any group cannot be converted. Groups and hierarchy are visible in the object tree. To convert, find the object you want to convert in the object tree and make sure it is within a group. Select it and verify visually in the scene that it is the correct object. Then right-click it (in the scene or in the tree), select **"Change type"** from the context menu, and choose **"Precise Seam"** from the dropdown list. https://github.com/user-attachments/assets/b29c87ea-adce-445c-b5ba-145f90e792c2 ### Changing the Modifier Type Once you have a Precise Seam modifier, you can change its type to any of the six available variants. Select the modifier in the tree or in the scene, right-click, and choose **"Precise Seam Type"** from the context menu — it will show a list of all Precise Seam modifier types. Select the one you need. <img alt="Context Menu" src="https://github.com/user-attachments/assets/cd72e91f-2873-4bb6-ab6c-50be1f43137a" /> ### Visual Distinction of Types Each Precise Seam type has its own color in the 3D view (all at 60% transparency): | Type | Color | Description | |------|-------|-------------| | Center | 🟠 Orange | Warm orange — primary Strong type | | Left | 🟡 Gold | Bright golden | | Right | 🟠 Dark Orange | Deep orange | | Enforced | 🟢 Green | Green — "allowed" zone | | Blocked | 🔴 Red | Red — "forbidden" zone | | Neutral | ⚪ Gray | Gray — neutral zone | Strong modifiers are visually unified with warm orange tones. Weak modifiers use intuitive colors: green = allowed, red = forbidden, gray = neutral. ### YouTube Full Demo Video Demonstrates the behavior of all six modifier subtypes and their application hierarchy based on their position in the object tree. [![Precise Seam Demo](https://img.youtube.com/vi/KEY9HMn_U4U/maxresdefault.jpg)](https://www.youtube.com/watch?v=F-In1N7AquQ) ## Test Files [Test Bell Object.zip](https://github.com/user-attachments/files/26289912/Test.Bell.Object.zip) This test file was created by drawing a spline curve on the surface of the printed object, then sweeping a triangular profile along it (Swept Boss/Base in SolidWorks). This way the seam follows the desired trajectory precisely. A circular profile can also be used as the sweep cross-section — this avoids orientation issues. [Big Test.zip](https://github.com/user-attachments/files/26383749/Big.Test.zip) Another file demonstrating all modifier types. > [!NOTE] > These test files have only been verified on Windows. Testing on Linux (AppImage/Flatpak) and macOS would be greatly appreciated — please share your results in the comments. ## Debug Instruments A debug branch that dumps geometry data to files: https://github.com/DImagine/OrcaSlicer/tree/feature-precise-seam-debug Python scripts for data visualization: [Precise Seam Python Visual Debug.zip](https://github.com/user-attachments/files/26330531/Precise.Seam.Python.Visual.Debug.zip) ## Feature Development Progress Log Claude Code and Codex were actively used during feature development. Progress data was saved at each stage. This information is included for reference, as it may be helpful for understanding the algorithm's internals. [Precise Seam Progress Log.zip](https://github.com/user-attachments/files/26289946/Precise.Seam.Progress.Log.zip) ## Related Issue Closes #11162 ## Changelog - 2026-03-27: Added handling for multiple intersection edge case - 2026-03-28: Added pop-up warning message if multiple intersections are detected - 2026-03-28: Improved detection and handling of multiple intersections, refined user notifications for problematic modifiers - 2026-03-29: Some minor updates and improvements - 2026-03-31: Refactor PreciseSeam based on AI code review findings

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Reference: github/OrcaSlicer#134