Brushes

A brush is jackdaw’s primitive for level geometry. Think TrenchBroom or old-school Hammer: convex polyhedra defined by their faces, with per-face materials and UVs, edited in place without a DCC tool. They serialize directly into the scene .jsn, no external mesh files.

The two ways to make a brush

Quick add

Hierarchy panel, right-click, Add > Cube or Add > Sphere. You get a unit primitive at the origin, selected and ready to move. This is the fastest path when you just need a block.

Draw

Press B to enter the draw-brush modal. Click in the viewport to drop vertices, then press Enter to close the polygon and extrude it to a brush. While drawing:

• Click places a vertex.
• Backspace removes the last vertex.
• Enter closes the polygon.
• Esc or right-click cancels.
• Tab toggles between additive and subtractive draw mode. In subtractive mode (C to enter directly), the closed polygon CSGs out of the brush you draw against.

The plane you draw on is the closest face under your cursor, or the world floor if nothing is under it.

Editing a brush

Select a brush, then pick the edit mode:

• 1 vertex mode
• 2 edge mode
• 3 face mode
• 4 clip mode

Click an element to select it, drag the gizmo to move it. Multi-select with Shift+Click. Delete removes the selected element (vertices collapse the surrounding face, faces leave a hole jackdaw won’t render).

Esc exits edit mode and returns to entity-level selection.

Snap and constrain

• Ctrl while dragging toggles snap to grid; the snap step follows your current grid size.
• X / Y / Z constrain the drag to that axis.
• MMB toggles the global snap mode without holding Ctrl.

Clip

Clip mode (4) draws a plane through the brush. Drag the plane gizmo where you want the cut, press Enter to apply. The brush splits in two; the clipped-off side becomes a new brush you can immediately delete or move.

Boolean operations

Select two or more brushes and run one of:

• CSG Subtract (Ctrl+K): cut the second selection out of the first.
• CSG Intersect (Ctrl+Shift+K): keep only the volume both brushes share.
• Join (Convex Merge) (J): merge two brushes back into one convex brush, when their union is itself convex.

All three live under the Edit menu. They run through the CSG code in crates/jackdaw_geometry. The result replaces the inputs with new brushes; the original selection ordering picks which is the minuend in subtract.

Faces, materials, and UVs

Selecting a face in face mode (3) shows its material and UV controls in the inspector. You can:

• Set a texture or material from the material browser.
• Tweak UV offset, scale, and rotation per face.

Face data lives on the brush entity as BrushFaceData. See Materials & Textures for what the material picker exposes.

Common gotchas

• Brush disappears after a CSG op. The op produced a degenerate result (zero-volume intersection, fully consumed subtractor). Undo and try a different overlap.
• Faces look inside-out. Brushes assume outward normals. If you authored vertices in clockwise order while drawing, flip the brush via the inspector or redraw.
• Snap is “wrong”. Snap follows the grid size shown in the status bar, not a fixed unit. Step the grid with [ and ].