mattercontrol/research/06-slicing-system.md

Slicing System

Summary

MatterControl integrates the MatterSlice slicing engine to convert 3D models into G-code instructions for printing. The system maps printer settings to slicer parameters, handles multi-extruder configurations, and supports features like rafts, supports, and custom start/end G-code.

Technical Description

Architecture Overview

PrinterConfig.Settings
       │
       ▼
EngineMappingsMatterSlice (IObjectSlicer)
       │
       ├── Settings Mapping (Exports dictionary)
       │
       ▼
   MatterSlice Engine
       │
       ▼
   G-code Output File

Slicer Static Class

The Slicer static class provides helper methods:

Key Methods:

Method	Purpose
SliceItem()	Entry point for slicing objects
GetExtrudersUsed()	Determine which extruders are needed
GetSolidsForExtruder()	Filter objects by extruder assignment
GetAllHoles()	Find hole/negative objects
T1OrGreaterUsed()	Check if multi-extruder print

Configuration:

• RunInProcess - Run slicer in-process (debug) vs subprocess

EngineMappingsMatterSlice

Implements IObjectSlicer interface to translate MatterControl settings to MatterSlice parameters:

Export Mapping:

Exports = new Dictionary<string, ExportField>()
{
    [SettingsKey.layer_height] = new ExportField("layerThickness"),
    [SettingsKey.perimeters] = new ExportField("numberOfPerimeters"),
    [SettingsKey.fill_density] = new ExportField("infillPercent", transformer),
    // ...
};

Mapping Categories:

Category	Sample Settings
Layer	layer_height, first_layer_height
Perimeters	perimeters, external_perimeter_speed
Infill	fill_density, infill_type, fill_angle
Speed	travel_speed, perimeter_speed, infill_speed
Retraction	retract_length, retract_speed, retract_lift
Support	support_material_spacing, support_air_gap
Raft/Brim	create_raft, raft_air_gap, skirts
Fan	min_fan_speed, max_fan_speed, bridge_fan_speed
Extruder	filament_diameter, nozzle_diameter, extrusion_multiplier

Export Field Transformers

Some settings require transformation:

// Percentage to decimal conversion
[SettingsKey.fill_density] = new ExportField(
    "infillPercent",
    (value, settings) => {
        if (double.TryParse(value, out double infillRatio))
            return $"{infillRatio * 100}";
        return "0";
    })

// Start G-code processing
[SettingsKey.start_gcode] = new ExportField(
    "startCode",
    (value, settings) => StartGCodeGenerator.BuildStartGCode(settings, value))

Multi-Extruder Support

Extruder assignment based on MaterialIndex:

var itemsThisExtruder = meshItemsOnBuildPlate.Where((item) => {
    var material = item.WorldMaterialIndex();
    return material == extruderIndex
        || (extruderIndex == 0 && material >= extruderCount);
});

Extruder-Specific Settings:

• support_material_extruder
• support_material_interface_extruder
• raft_extruder
• brim_extruder

Print Output Types

Objects can have different output behaviors:

Type	Description
Default	Normal solid printing
Solid	Explicitly solid
Support	Support material
Hole	Negative/subtraction
Fuzzy	Fuzzy skin effect

Slicing Process

1. Collect Printable Items: Filter scene for printable objects
2. Determine Extruders: Calculate which extruders are needed
3. Map Settings: Convert settings to slicer parameters
4. Run Slicer: Execute MatterSlice engine
5. Progress Reporting: Update UI with slice progress
6. Output G-code: Write to file

MatterSlice Integration

MatterSlice is included as a submodule:

• Submodules/MatterSlice/MatterSlice.csproj
• Submodules/MatterSlice/MatterSliceLib/MatterSliceLib.csproj

Key Settings Files:

• StaticData/SliceSettings/Layouts.txt - UI layout definitions
• Settings JSON files in printer profiles

Slicer Settings UI

Settings are organized via SliceSettingsWidget:

SliceSettingsWidget
├── Category tabs (General, Infill, Support, etc.)
├── Settings rows (SliceSettingsRow)
└── Preset selector (PresetSelectorWidget)

Design Rationale

Integrated Slicer: Bundling MatterSlice provides:

• Seamless user experience
• Direct control over slicing behavior
• No external dependencies to manage
• Consistent cross-platform behavior

Export Field Pattern: The mapping dictionary allows:

• Declarative settings mapping
• Custom transformers where needed
• Easy addition of new settings
• Clear documentation of mappings

Extruder Detection: Pre-calculating used extruders enables:

• Appropriate temperature settings
• Correct tool change G-code
• Optimized print preparation

Reference

Core Classes

Class	Location	Description
Slicer	SlicerConfiguration/Slicer.cs	Static slicer helpers
EngineMappingsMatterSlice	SlicerConfiguration/EngineMappingsMatterSlice.cs	Settings mapping
ExportField	MatterControl.Printing/ExportField.cs	Field definition
SliceSettingsWidget	SlicerConfiguration/SliceSettingsWidget.cs	Settings UI

UI Components

Class	Location	Description
SliceSettingsRow	SlicerConfiguration/SliceSettingsRow.cs	Individual setting row
PresetSelectorWidget	SlicerConfiguration/PresetSelectorWidget.cs	Preset dropdown
SettingsRow	SlicerConfiguration/SettingsRow.cs	Base row widget

Key Enums

Enum	Values
PrintOutputTypes	Default, Solid, Support, Hole, Fuzzy
InfillType	Grid, Triangles, Gyroid, Lines, etc.
SeamPlacement	Random, Nearest, Aligned
SupportType	None, Lines, Grid, FromBed, Everywhere

Settings Keys (Sample)

Key	Description
layer_height	Layer thickness
perimeters	Number of perimeter shells
fill_density	Infill percentage
support_material	Enable supports
create_raft	Create print raft
retract_length	Retraction distance
travel_speed	Non-printing move speed