OrcaSlicer/docs/ZAA.md

Z Anti-Aliasing (ZAA) — Z Contouring

ZAA eliminates stair-stepping on curved and sloped top surfaces by adjusting the Z height of each extrusion point to follow the actual 3D model surface.

Instead of printing flat horizontal layers, ZAA raycasts each point of the toolpath against the original mesh and micro-adjusts its Z coordinate to match the true surface geometry. The result is visibly smoother surfaces on domes, chamfers, and shallow slopes — without post-processing.

This is a port of the ZAA implementation from BambuStudio-ZAA by adob.

Configuration

ZAA adds five settings under Print Settings > Quality:

Setting	Type	Default	Description
zaa_enabled	bool	off	Master enable/disable switch
zaa_min_z	float	0.06 mm	Minimum Z layer height; also controls the slicing plane offset
zaa_minimize_perimeter_height	float	35°	Reduce perimeter heights on slopes below this angle (0 = disabled)
zaa_dont_alternate_fill_direction	bool	off	Keep fill direction consistent instead of alternating per layer
zaa_region_disable	bool	off	Disable ZAA for a specific print region/material

How It Works

1. The slicer slices normally, then runs a posContouring step on each layer.
2. ContourZ.cpp raycasts every extrusion point vertically against the source mesh.
3. Each point's Z is adjusted to the mesh intersection, converting flat Polyline paths into Polyline3 paths that carry per-point Z coordinates.
4. The G-code writer emits the adjusted Z values, so the printer follows the true surface.

Key Implementation Details

• Core algorithm: src/libslic3r/ContourZ.cpp (~330 lines)
• 3D geometry: Point3, Line3, Polyline3, MultiPoint3 extend the existing 2D types
• Pipeline step: posContouring in PrintObject.cpp, runs after perimeter/infill generation
• G-code output: GCode.cpp writes per-point Z when path.z_contoured is set
• Arc fitting: Templated to work with both 2D and 3D geometry
• ExtrusionPath change: polyline field changed from Polyline to Polyline3

Testing

1. Load a model with curved top surfaces (spheres, domes, chamfered edges)
2. Enable Z contouring in Print Settings > Quality
3. Slice and inspect the G-code — Z values should vary within each layer on contoured surfaces