Extrude
The Extrude tool extends selected regions of a surface outward (or inward) by creating new geometry that connects the original boundary to a transformed copy of the selected area. This interactive operation combines region selection with full 3D transformation controls for precise extrusion results.
Overview
Extrusion is a fundamental 3D modeling operation that creates new geometry by "pulling" or "pushing" a surface region in a specified direction. The tool provides a complete workflow for:
- Selecting the region to extrude using ROI (Region of Interest) tools
- Interactively positioning and transforming the extruded geometry
- Generating connecting geometry between original and extruded surfaces
Common applications include:
- Adding features: Creating protrusions, handles, or extensions
- Modeling modifications: Extending existing geometry in new directions
- Design iteration: Quickly testing different extension options
- Surface modification: Adding material to specific regions
Accessing the Tool
Navigate to the Surface ribbon tab and locate Extrude in the Edit section. Select a surface object before activating the tool. The active surface becomes the target for the extrusion operation.
Workflow Overview
The extrusion process follows a structured workflow:
Step 1: Select the Region
Use the ROI (Region of Interest) selection tools to define which triangles will be extruded:
- Enable the ROI selection tool from the controls panel
- Paint or select the desired triangles on the surface
- Disable the ROI selection tool when selection is complete
The selected region defines the "cap" of the extrusion—the portion that will be duplicated and transformed.
Step 2: Start Extrude Interaction
Click the Start extrude interaction button to begin the interactive extrusion:
- A 3D manipulator appears for interactive control
- Transform values become editable in the controls panel
- The preview updates in real-time as you adjust parameters
Step 3: Adjust the Transformation
Transform the extruded region using either:
- Interactive manipulator: Drag the gizmo handles in the 3D view
- Direct value entry: Type precise values in the transform fields
Step 4: Apply the Extrusion
Click Apply to finalize the extrusion:
- New geometry is created connecting the original and extruded regions
- The surface is modified with the added extrusion
- The operation can be undone if needed
Transformation Parameters
The tool provides full control over the extrusion transformation:
Translate Distance
Controls the displacement of the extruded region from its original position:
| Axis | Description |
|---|---|
| X | Translation along the X-axis (mm) |
| Y | Translation along the Y-axis (mm) |
| Z | Translation along the Z-axis (mm) |
Positive values move in the positive axis direction; negative values move in the negative direction. The translation is applied in world coordinates.
Rotate Angle
Controls the rotation of the extruded region around each axis:
| Axis | Description | Range |
|---|---|---|
| X | Rotation around the X-axis (degrees) | -180° to 180° |
| Y | Rotation around the Y-axis (degrees) | -180° to 180° |
| Z | Rotation around the Z-axis (degrees) | -180° to 180° |
Rotation is applied around the center of the selected region, allowing the extrusion to curve or twist.
Scale Factor
Controls the scaling of the extruded region relative to its original size:
| Axis | Description | Default |
|---|---|---|
| X | Scale factor along X-axis | 1.0 |
| Y | Scale factor along Y-axis | 1.0 |
| Z | Scale factor along Z-axis | 1.0 |
- Values > 1.0: Enlarge the extruded region
- Values = 1.0: Maintain original size
- Values < 1.0: Shrink the extruded region
- Negative values: Mirror the geometry along that axis
Scaling is applied from the center of the selected region.
Region Selection
ROI Selection Tools
The integrated ROI (Region of Interest) tools allow precise selection of triangles to extrude:
- Brush selection: Paint triangles with adjustable brush size
- Rectangle selection: Select triangles within a rectangular region
- Polygon selection: Define a custom selection boundary
- Select all: Select all triangles in the surface
- Invert selection: Switch selected and unselected triangles
Selection Tips
For effective region selection:
- Use appropriate brush size: Larger brushes for broad regions, smaller for detailed selection
- Zoom in for precision: Closer views allow more accurate triangle selection
- Use inversion strategically: Select the smaller region and invert if easier
- Check from multiple angles: Ensure all desired triangles are included
Practical Applications
Creating a Handle
- Select a rectangular region on a surface
- Start extrude interaction
- Translate outward from the surface
- Apply slight scale reduction (0.9-0.95) for tapered handles
- Apply the extrusion
Adding a Flange
- Select the edge region of a surface
- Start extrude interaction
- Translate perpendicular to the surface
- Optionally scale to widen the flange
- Apply the extrusion
Creating Curved Extensions
- Select the region to extend
- Start extrude interaction
- Apply both translation and rotation
- The connecting geometry will curve to accommodate the transformation
- Apply the extrusion
Stepped Extrusions
For multi-step extrusions:
- Complete the first extrusion
- Select the newly created cap region
- Perform another extrusion with different parameters
- Repeat as needed for complex stepped geometry
Technical Considerations
Connecting Geometry
The tool automatically generates triangulated geometry connecting the original boundary to the transformed boundary. The quality of this connecting geometry depends on:
- Boundary complexity: Simple boundaries produce cleaner connections
- Transformation magnitude: Large rotations or non-uniform scales may create stretched triangles
- Original mesh quality: Well-shaped boundary triangles produce better connections
Self-Intersection
Extreme transformations (large rotations or scales) may cause the connecting geometry to self-intersect. If this occurs:
- Reduce transformation magnitude
- Apply multiple smaller extrusions instead
- Use the Diagnostics and Fixes tool afterward to check for issues
Topology Requirements
The tool works best when:
- The selected region forms a connected patch
- The boundary is a simple loop (no branches)
- The region is not too close to surface boundaries
Performance
Extrusion performance depends on:
- Selection size: Larger selections take longer to process
- Mesh complexity: Higher resolution meshes require more computation
- Transformation preview: Real-time preview may lag for very large selections
Common Issues and Solutions
| Issue | Likely Cause | Solution |
|---|---|---|
| No visible extrusion | Zero translation values | Set non-zero translation |
| Self-intersecting result | Extreme transformation | Reduce transformation magnitude |
| Disconnected extrusion | Selection not contiguous | Ensure connected region selection |
| Poor connecting triangles | Complex boundary shape | Simplify selection boundary |
| Manipulator not visible | Interaction not started | Click "Start extrude interaction" |
| Preview not updating | Large selection | Wait for processing; reduce selection size |