3D Composition Modes — Add, Cut, and Attach
Build stairs, sunken channels, and surface-following inlays by linking 3D shapes as parent-child pairs with Add, Subtract, or Attach.
3D Composition Modes — Add, Subtract, and AttachComposition modes are set in the Inspector for a child shape — the shape that was selected second during the Stack operation. The parent shape is shown with a dashed blue outline when the child is selected.
The three modes:
| Mode | Description | Typical use | |------|-------------|-------------| | Add | Child sits on top of parent's top face. Combined volume is additive. | Steps, raised copings, stacked planters | | Cut | Child's footprint and height create a void in the parent. | Sunken areas, drain channels, openings | | Attach | Child connects to the parent face at its exact current position. No height merge — parent geometry is unchanged. | Surface-mounted details, decorative panels, inlaid features |
Composition mode can be changed at any time after the Stack operation — the geometry updates immediately.
Viewing and changing a child shape's composition mode
Select the child shape in the 3D view by clicking it. The parent shape highlights with a dashed blue outline to indicate the relationship.
In the Inspector sidebar, scroll to the Composition section. A dropdown shows the current mode: Add, Cut, or Attach.
Click the dropdown to change the mode. The 3D view updates immediately to show the new composition result.
If a shape has no parent (it was not stacked onto another shape), the Composition section is not shown in the Inspector.
To see which shape is the parent, select the child and look for the dashed blue outline — that is the parent. You can also click the parent indicator label in the Inspector to navigate directly to the parent shape.
Add mode — additive stacking
Add is the default mode when shapes are combined using the Build stack operation.
In Add mode:
- The child's base aligns with the parent's top face
- The child's volume is added on top of the parent
- The combined form renders as a contiguous 3D solid
- The child's material covers its top and side faces independently from the parent
- Height offsets stack: the overall height of the combination is the parent height plus the child height
Rendering in Add mode: The junction between parent and child is seamless — no gap, no visible seam. The two shapes behave as a single solid in 3D and in rendered views.
Material behavior: The parent's top face material is hidden under the child footprint. The child's own top face material and side face material are visible. Areas of the parent's top face not covered by the child retain the parent's top material.
When building a staircase, use Add mode for each tread stacked on the previous step. The result is a stair structure where each tread's material is independently controllable.
Cut mode — subtractive void
Cut is the mode applied when shapes are combined using the Dig stack operation.
In Cut mode:
- The child's footprint is cut out of the parent's volume
- A void is created in the parent wherever the child overlaps — visible as an opening or depression
- The child shape itself is hidden in the final render — only the void it creates in the parent is visible
- The void depth equals the child's extrusion height. If the child is taller than the parent, the cut goes all the way through.
Rendering in Cut mode: The interior walls of the void are rendered using the parent's side face material (since they are part of the parent's geometry after the cut). The child shape's own materials are not visible.
Child shape visibility: The child shape can optionally be made visible as a separate element — for example, showing the inset object inside the cut pocket. Toggle Show Child Geometry in the Composition section of the Inspector.
Attach mode — surface connection without merge
Attach mode connects the child to the parent at its current absolute position without modifying the parent's geometry.
In Attach mode:
- The parent's shape is completely unaffected — no volume added, no void created
- The child sits at its own absolute height (set independently, not relative to the parent's top face)
- The child moves with the parent when the parent is repositioned — the two stay linked
- The child can be positioned partially inside the parent's volume (e.g., a decorative panel inset into a wall face)
Common uses for Attach:
- Surface-mounted ornamental panels on a wall
- Inlaid feature strips in a paving surface
- Structural elements that must move together but not merge geometrically
Attach is the right mode when you want the child to be a companion of the parent without being structurally subordinate to it.
Attach mode is useful for placing decorative coping blocks along the top of a wall — the blocks sit at the exact position you place them, travel with the wall if you move it, but do not add to the wall's height or affect its geometry.
Fine-tune offset and blend radius
In the Link Details panel, the Offset slider shifts the child vertically relative to the parent surface — drag it positive to raise the child above the parent top, or negative to sink it partially into the parent. The Blend Radius slider controls the edge softness where child and parent meet: a small value (3–5 cm) produces a crisp junction, while a larger value creates a gentle rounded transition. For Subtract operations, the Carve Mode dropdown lets you choose Carve Down From Surface (void depth is relative to the parent's top) or Carve to Absolute Z (void extends to a fixed world elevation).
Disconnect or disable a link
To temporarily hide a child's effect without deleting the link, click the eye icon beside the child row in the Composition Inspector tree. To permanently remove the parent-child relationship, click the three-dot menu beside the child row and choose Disconnect. After disconnecting, the child becomes an independent shape at its own world position and the parent returns to its unmodified geometry. Individual links can also be set to None in the Operation dropdown, which disables the link while preserving all settings for later restoration.
You can nest composition links multiple levels deep. For example, a raised platform (Add) can itself be the parent of a decorative channel (Subtract) and a surface-mounted paving inlay (Attach with Wrap surface mode) — each level is independently configurable in the Composition Inspector tree.
Disconnecting a link is permanent and cannot be undone after the session is closed. If you want to temporarily suppress a child's effect, disable it with the eye icon instead — this preserves all link settings and can be re-enabled at any time.
Keyboard Shortcuts
| Key | Action |
|---|---|
| S | Activate Stack tool (Build / Dig / Wrap) |
| Ctrl+Z | Undo last stack or link operation |
Frequently Asked Questions
What is the difference between Add and Attach?
Add merges the child's volume into the parent to form a single combined solid — the child geometry becomes part of the parent mass. Attach places the child on top of the parent surface without modifying the parent's shape at all; the child is a separate object that simply follows the parent's elevation. Use Add for structural features like steps or raised copings, and Attach for decorative surface objects like inlays, markers, or furniture that should track elevation changes.
Can I change the operation after linking?
Yes. Open the Composition Inspector, click the child node, and change the Operation dropdown at any time. The geometry updates immediately. All other link settings (offset, blend radius, surface mode) are preserved when you switch operations.
What does Carve Mode do for Subtract operations?
Carve Mode controls how deep the subtraction goes. 'Carve Down From Surface' measures the void depth downward from wherever the parent's top surface is at each point — useful when the parent has a sloped or curved top and you want the channel to be a consistent depth. 'Carve to Absolute Z' cuts through to a fixed world elevation regardless of the parent surface height, which is useful for creating a flat-bottomed pond or drain channel.
Can a shape be a child of more than one parent?
No. The composition graph enforces a strict tree structure — each child can have at most one parent. To apply the same shape's footprint to multiple parents, duplicate the shape and link each copy to the intended parent separately.
Why does Wrap not seem to have any effect?
Wrap mode only produces a visible difference when the parent has a non-flat top surface — such as a dome, ridge, pyramid, or height-points mound. If the parent top is completely flat, the wrapped and non-wrapped results look identical. Try increasing the parent's top surface curvature or switching the parent's Top Surface preset to Dome or Ridge to see the wrap effect clearly.