Blender Geometry Nodes: A Guide to Boolean and Extrude for Architecture

Blender’s current online manual explains how the Mesh Boolean and Extrude Mesh Geometry Nodes work, along with the Boolean modifier and SDF Grid Boolean node. This guide covers when to use each method for cutting, joining, creating openings, and extending surfaces in architectural and interior models. Since the source pages do not specify a particular Blender version number, this article is limited to information on the manual’s “latest” pages.

1. Choose a method before starting a Boolean operation

Boolean operations change an object’s shape by cutting or joining geometry. The Mesh Boolean Node offers three basic operations on two geometry inputs:

• Intersect: Keeps the volume shared by both inputs.

• Union: Joins the geometries and removes internal elements.

• Difference: Subtracts the second geometry from the first.

Choose the operation based on the intended result—for example, creating an opening in a wall, cutting a section from a furniture body, or joining two masses. For Difference, check which geometry is being subtracted and which is the base, since the result is calculated by subtracting the second input from the first.

The Solver option in the Mesh Boolean node also affects the result and processing time. Float is a simple, faster method, but it does not support overlapping geometry. Exact can produce more comprehensive results when surfaces are coplanar or otherwise overlap, but it is significantly slower. The Manifold solver is generally the fastest option, but it only works with manifold meshes. The manual also notes a special case in which a plane is used for a Difference operation.

2. Check the solver and mesh conditions

The Boolean modifier manual emphasizes that reliable results are guaranteed with manifold meshes. Non-manifold geometry, especially meshes with holes, often works but can produce unexpected artifacts and errors. The Manifold solver will not work at all with non-manifold meshes. So when you run into problems, inspect the input topology rather than simply switching solvers.

The choices in this table are not an automatic recipe for every scene. In particular, rather than enabling Hole Tolerant for every Boolean operation, follow the manual’s recommendation and use it when the Exact solver encounters errors due to non-manifold geometry. Overlap Threshold in the Float solver determines how close surfaces must be to count as overlapping. If Float does not produce the expected result, the manual recommends trying the Exact solver.

In the Boolean modifier, the source can be a single Object or a Collection. The Collection option uses multiple mesh objects as the source. Note that the Intersect operation is unavailable when the Float solver is selected. The Exact solver includes Self Intersection and Hole Tolerant options; for material transfer, it offers the Index Based and Transfer methods.

3. Extend surfaces or edges with Extrude Mesh

The Extrude Mesh Node creates new edges or faces from selected mesh elements and moves them by a specified Offset. The Selection field determines which elements are extruded. Offset sets the translation vector, while Offset Scale controls its magnitude. By default, the direction follows the element’s normal. If all elements need to move in the same direction, the manual notes that connecting a Vector Node to Offset can improve performance by bypassing normal calculation.

Follow these steps when using the node:

1. Set the Selection field. Include only the elements you want to extend. This applies the operation to the target area rather than the entire mesh.

2. Choose a mode for the geometry. Vertices mode creates a new, independent edge for each selected vertex. Edges mode adds new quad faces to selected edges. Faces mode extends selected face regions.

3. Set how face operations are grouped. When Individual is false, adjacent face regions are extruded together and side faces are created along their boundaries. When Individual is enabled, each face is extruded separately.

4. Check the Offset and its scale. If the default normal direction differs from the intended direction, adjust the Offset vector. For operations along a shared direction, consider the manual’s performance note and use a Vector Node.

5. Inspect the resulting topology. In Face mode, the node does not preserve the back faces of the extrusion; they are removed. In Edge mode, the normals of new faces can be ambiguous depending on the situation, so you may need to check them afterward.

When the whole mesh is selected and the mesh is already manifold, the Face mode operation can change the size of the entire shape. So, before extending a façade panel or furniture surface, verify the scope of the Selection. The node’s Top and Side outputs are Boolean fields identifying the resulting top and side elements; the documentation shows that these fields can be used for tasks such as assigning materials to faces.

4. When should you use SDF Grid Boolean?

SDF Grid Boolean performs Boolean operations on Signed Distance Field (SDF) grids rather than meshes. Intersect keeps the shared region, Union combines the volumes, and Difference subtracts the second input from the first. This method works directly with volumetric shapes and, according to the manual, can produce smooth, continuous results. The output can be converted to a mesh with the Grid to Mesh node or used in other volume operations.

So, don’t think of the SDF approach as the same workflow as Mesh Boolean, which operates directly on mesh topology: one works with mesh inputs, the other with SDF grids. The manual does not provide detailed resolution or performance figures for SDF grids, so it is not possible to make fixed recommendations about those settings.

Common mistakes

• Using the Manifold solver with non-manifold inputs: This solver does not work with these meshes. Check the geometry or try another solver.

• Expecting precise results from Float with overlapping surfaces: Float does not support overlapping geometry. According to the manual, Exact may be an alternative, but it is slower.

• Enabling Hole Tolerant unnecessarily: This option increases processing time; consider it when the Exact solver encounters problems with non-manifold geometry.

• Failing to check selection or direction in Extrude Mesh: Check Selection and Offset after applying the operation, and remember that back faces are not preserved in Face mode.