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Drawing: Layers, Pens and Line Styles

The MaStro Drawing section of the Properties editor contains three sub-panels — Layers, Pens, and Line Styles — that together define the appearance of every line in the drawing.

Layers panel

The layers list shows all layers defined in the scene. Each layer is a named record that groups edges by appearance.

Layer list

Each row shows the layer name, a visibility toggle, and a lock toggle. The active layer (highlighted) is the one whose attributes are assigned to newly extruded edges.

Use the + and − buttons to add or remove layers. Locked layers cannot be removed.

Layer properties (shown below the list when a layer is selected)

  • Name — display label; does not affect attribute storage.
  • Pen — drop-down showing enabled pens. Determines line weight and default colour.
  • Line Style — drop-down showing the available dash patterns.
  • Colour — stroke colour for this layer. When Use Pen Colour is active (link icon next to the colour), this value is kept in sync with the selected pen's colour.
  • Visible — when disabled, all edges on this layer produce no output in the Grease Pencil result.
  • Black — marks edges on this layer as candidates for Black Mode.

Toolbar row (below the list)

  • Sync — manually triggers a full update of all drawing mesh attributes and rebuilds the Geometry Nodes group. Use this when Auto Update is disabled.
  • Auto Update (refresh icon toggle) — when enabled, any change to a layer, pen, or line style propagates to the mesh attributes immediately.
  • Black Mode (solid shading icon toggle) — global override; see Black Mode below.

Header popover

The layer name shown in the 3D viewport header opens a popover with a compact layer list and the Assign Layer to Selected Edges button, which writes the active layer's ID and attributes to all selected edges across all drawing meshes currently in Edit Mode.

Pens panel

Each pen defines the physical weight and default colour of a line.

  • Thickness — in millimetres. Stored internally as a radius in metres (thickness / 2000).
  • Colour — used as the layer colour when Use Pen Colour is active on the layer.
  • Active toggle — disabled pens are hidden from the pen drop-down in the layer properties.
  • Locked toggle — prevents accidental edits.

Pens are sorted by thickness. Changing a pen's thickness or colour propagates immediately to all layers that reference it.

Line Styles panel

A line style defines the dash pattern of a stroke. Up to three dash–gap pairs are available:

Field Meaning
l1 Length of the first dash
g1 Gap after the first dash
l2 Length of the second dash
g2 Gap after the second dash
l3 Length of the third dash
g3 Gap after the third dash

A line style is continuous when g1, l2, g2, l3, and g3 are all zero. In this case l1 is ignored for resampling purposes and the edge is rendered as an unbroken stroke. All other configurations produce a dashed line, where the Geometry Nodes pipeline resamples the curve before applying the pattern.

Black Mode toggle

The Black Mode toggle (solid shading icon in the layer toolbar) is a global scene switch. When enabled, it writes True to the mastro_drawing_black_switch attribute on every edge of every drawing mesh. When disabled, it writes False.

In the Geometry Nodes pipeline, an edge is rendered in black only when both conditions are true:

  • The edge's mastro_drawing_black attribute is True (set because its layer has the Black flag enabled).
  • mastro_drawing_black_switch is True (the global toggle is on).

This design lets you prepare layers with the Black flag in advance and switch the entire drawing to black-line mode with a single click, without losing any layer-level colour information.

The black stroke uses the Mastro_GP_Black material, a solid black GP material created automatically on first sync.