Slice Tools: Constrained Slice


Constrained slice is an easy to use tool that allows you to use imported arch-viz plans (or any edge selection) to guide the slicing of your 3D models, e.g. to cut window and door positions into the shell of a building using the original CAD polylines/outlines to guide the position of each cut. This provides an alternative to using the boolean tools and can provide cleaner geometry if the original arch-viz plans are of a good standard.

This tool enforces strict vertical or horizontal cutting of your geometry to help prevent any errors in the orginal plans from being transferred into your 3D model. It also allows for lazy selection by automatically eliminating edges that would create identical cuts in the target geometry.

You can use this tool for other tasks and with any mesh items as it simply uses a selection of edges in one mesh item layer to guide the slicng of geometry in another mesh item layer.

How to useā€¦

  1. Click on “Slice Tools” to open the tool's UI
  2. Select two mesh items
  3. In the first mesh item, select one or more polygons (optional)
  4. In the second mesh item, select one or more edges
  5. Set options
  6. Rotate the 3D view, if required. Important: In perspective mode, cutting takes place from the selected edges in the direction of modo's workplane.
  7. Click “Slice: Vertical Edges” or “Slice: Horizontal Edges”

User Interface



You can choose between using edges from one mesh item (Edges from Single Item) or multiple mesh items (Edges from Multiple Items).
The multiple mesh items option is useful if you using arch-viz plans and have polylines/edges for a single elevation that are spread over several mesh items. In this case you would select one mesh item with the target geometry for slicing and two or more items containing the polylines/edges that will be used to guide the cutting/slicing.
Enable Warning Dialog
If some of the selected edges do not meet the criteria set, then a warning dialog is displayed to inform you why the edges were not used for cutting. Use this option to enable/disable the warning dialog.
Remove Duplicate Edges
Duplicates can be automatically eliminated, which allows for lazy selection. Here you specify the range within which the position of two or more edges are considered to be the same/duplicates.
For example, if you have selected three edges with very closely matching height values, then only one horizontal cut will be made when you apply the tool provided they all lie withing the range specified. This option prevents cuts from being made in close proximity, in the target geometry, due to small errors (e.g. drafting/drawing errors present in the original arch-viz plans).
Level Edges
If an edge is not precisely horizontal or vertical, then the average of the two edge vertex positions can be used provided that they fall within the specified distance. A value of zero disables this option.
Imagine you have selected an edge for horizontal cutting, but the edge is not quite level i.e. one vertex is slightly higher than the other. Provided they are within the specified distance the script will just take the average of the vertex heights and use that for cutting. This helps to prevent cutting edges that are not precisely horizontal or vertical.
Slice: Vertical Edges
Checks selected edges and uses those that are vertical (after removing duplicates and averaging those that are no precisely vertical) to cut the target geometry. Edges that are not considered vertical remain highlighted/unused.
Slice: Horizontal Edges
Checks selected edges and uses those that are horizontal (after removing duplicates and averaging those that are no precisely level) to cut the target geometry. Edges that are not considered horizontal remain highlighted/unused.


  • Edges that do not meet the selected criteria will remain highlighted. This helps to highlight errors.
  • Prefer to use constrained slice rather than unconstrained slice since it performs a number of extra checks that helps to prevent errors in the original edge selection (e.g. edges not straight or level, removal of duplicates etc.) before performing the slice.
  • You can switch to an appropriate orthogonal view before making the cuts, if preferred. This can be useful for making a lazy selection of many edges e.g. outlines of windows from a specific elevation.
  • Use small values, e.g. 1mm, for Remove Duplicates and Level Edges.


  • Cutting occurs in the direction of the workplane. If you activate the tool and see no effect, then check the position of the workplane. For example, if the workplace in on the ground the cut will occur directly down from the selected edge and will be unlikely to cut the target geometry.
  • Does not support X-up axis coordinate space.