Whether importing a mesh or creating one in-engine, you may need to edit the geometry. The PolyModel category in Modeling Mode consists of tools for performing granular mesh edits. These tools are useful for:
- Low-poly modeling.
- Hard-surface modeling.
- Blocking out levels.
Two of these tools, PolyEd (PolyGroup Edit) and PolyDef (PolyGroup Deformation), perform edits using a mesh's PolyGroups.
PolyModel Tools
Understanding PolyGroups
PolyGroups are a set of grouped triangles. You can use the groups for:
- UV layout.
- Material organization.
- Modeling and deformation.
- Traditional box modeling.
PolyGroups are automatically generated on meshes in the Shapes category. You can also create them using GrpPnt (PolyGroup Paint), GrpGen (PolyGroup Generate), or TriSel (Triangle Select) tool.
Before you start using the PolyModel tools, we recommend reviewing the Understanding PolyGroups documentation to learn more about PolyGroups and how to create them.
Using PolyModel Tools
PolyGroup Edit
The PolyEd (PolyGroup Edit) tool includes a suite of operations for editing a mesh with PolyGroups. Common operations such as Extrude, Bevel, Weld, and Bridge are available. Also included are operations that only work with structured PolyGroups, such as Insert Edge Loop and edge loop/ring selection.
Combining all these tools with PolyGroup-specific operations like Merge (groups) or Simplify By Groups creates a low polygon workflow commonly associated with Digital Content Creation (DCC) software such as 3ds Max, Blender, or Maya.
Meshes with no PolyGroup information cannot be used with this tool.
You can control which component of your mesh you want selectable by using the Selection Filter.
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| Select vertices | Select edges | Select faces | Select edge loops | Select a ring of edges |
PolyEd's editing operations are grouped into three categories: Face Edits, Shape Edits, and Edge Edits.
| Operation | Description |
|---|---|
| Face Edits | |
| Extrude | Extrudes geometry from the set of selected faces by moving and stitching them. Mouse movement controls extrude height and depth. Click in the viewport to complete the extrusion. |
| Offset | Offsets geometry from the set of selected faces. Mouse movement controls offset distance. Click in the viewport to complete the offset. |
| Push Pull | Faces can cut away the mesh or bridge mesh parts. |
| Inset | Insets the current set of selected faces. Mouse movement controls the inset distance. Click in the viewport to complete the inset. |
| Outset | Expands the set of selected faces out. Mouse movement controls the outset distance. Click in the viewport to confirm the outset distance. |
| Bevel | Slants the edge loops around the selected faces. |
| Delete | Removes the set of selected faces. It can also be used with the Backspace and Delete keys. |
| Merge | Combines the set of selected faces into one, creating a new PolyGroup. |
| Cut Faces | Cuts the set of selected faces. Click once in the viewport to create an initial cutting vertex, and click again to set the cut line. |
| Recalc Normals | Recalculates normals for the current set of selected faces. |
| Flip | Flips normals and face orientation for the current set of selected faces. |
| Retriangulate | Retriangulates each of the selected faces. |
| Decompose | Splits each of the selected faces into a separate polygon for each triangle. |
| Disconnect | Separates the selected faces at their borders. |
| Duplicate | Duplicates the selected faces at their border. |
| Shape Edits | |
| Insert Edge Loop | Inserts a chain of edges across quads in a mesh. Edges will not be inserted on non-quad faces. |
| Insert Edge | Adds an edge(s) connecting existing edges or vertices across a single face. |
| Simplify by Groups | Simplifies every polygon group by removing vertices on shared straight edges, then retriangulates. |
| Edge Edits | |
| Weld | Merges selected edges, moving the first edge to the second. |
| Straighten | Makes each selected PolyGroup edge follow a straight path between its endpoints. |
| Fill Hole | Fills the adjacent hole for any selected boundary edges. |
| Bevel | Slants the selected edges, replacing them with angled faces. |
| Bridge | Creates a new face that connects the selected edges. |
Many operations have a secondary set of settings that open upon selection.
While using PolyEd, you can interactively set UVs using Planar Projection. To scale the UV island, drag the cursor in and out. To learn more about creating and editing UVs, see UV Category.
PolyGroup Deformation
The PolyDef tool dynamically alters the shape of a mesh through its PolyGroups. Deformation is an efficient way to reshape a mesh quickly and create organic geometry.
You can choose between two deformation types:
- Linear, where PolyGroup edges connected to the selected component remain straight.
- Smooth, where PolyGroup edges connected to the selected component are smoothly interpolated into a curve.
To transform the mesh, click and hold the selected component (edge, face, or vertice).
If your mesh does not deform as expected, your resolution (triangle count) may be too low. You can use the Remesh tool to retriangulate.
To learn more about the different deformation tools in Modeling Mode and workflow tips, see Deform Category.
Cube Grid
The CubeGr (Cube Grid) tool creates blockout meshes using a repositionable grid. You can use CubeGr to create a new mesh or edit the selected mesh.
The Push and Pull actions are helpful in quickly building level prototypes.
What makes CubeGr an efficient tool for blockout are the operations coupled with hotkey commands. Below are hotkeys for building out your grid and adjusting its size.
| Hotkey | Description |
|---|---|
| Click | Makes a grid selection. |
| Click + Drag | Dynamically creates an array of rows and columns. |
| Shift + Click | Creates an array of rows and columns between the initial and second position clicked. |
| Ctrl + E | Increases the grid size. |
| Ctrl + Q | Decreases the grid size. |
| Shift + E | Shifts your selection forward one grid cell. |
| Shift + Q | Shifts your selection backward one grid cell. |
Once your grid is selected you can use the Actions buttons or use the following hotkeys to build your mesh.
| Hotkey | Description |
|---|---|
| Ctrl + Drag | Push or pull geometry from the selected grid. |
| E | Pull geometry from the selected grid. |
| Q | Push from the selected grid. |
| Z | Enter Corner Mode where you can select corners of your selected grid that are pushed or pulled by Ctrl + Drag or E/Q. Press Z again to apply the change. |
The grid can be repositioned by using the grid gizmo (toggled with the R key) or by Ctrl + Middle Click, which will move the gizmo to the corner of the nearest cell. You can also set specific position and orientation in the Modeling panel, or reinitialize from the transform of a created mesh.
See Shortcut Info in the Modeling panel to learn more about the various hotkeys for the tool.
After you finish editing the mesh you can choose the following Output Types:
- Static mesh
- Dynamic mesh
- Volume
To learn more about the Output Types and their use cases see Working with Meshes.
Mesh Bool
The MshBool (Mesh Bool) tool subtracts or adds mesh pairs. It is useful for quickly adding detail and displacement effects to your mesh.
Two meshes are required to use the tool as the resulting mesh change revolves around the area where both meshes intersect. The order in which you select the meshes matters for the first two operations:
- Your first selection becomes A.
- Your second selection becomes B.
You can choose from four operations shown in the table below.
| Operation | Description |
|---|---|
| Difference A - B | Subtracts the second mesh from the first mesh. |
| Difference B - A | Subtracts the first mesh from the second mesh. |
| Intersection | Subtracts non-overlapping geometry. |
| Union | Combines both meshes and resolves self-intersections. |
Once both meshes are selected, and the tool is activated, you can interactively manipulate one or both meshes in the Viewport, depending on the operation.
When you are done editing the mesh, you can decide how to handle the mesh output using the operations shown in the table below.
| Operation | Description |
|---|---|
| Output Type | Chooses the type of Actor to create. Only available if New Object is selected in Output Object. |
| Output Object | Determines if a new Actor is created, or if the output is based on the selected meshes. |
| On Tool Accept | Determines what happens to the selected meshes on when changes are accepted. |
Mesh Cut
The MshCut (Mesh Cut) tool splits one mesh into parts using a second mesh. You can use the tool to break up meshes into smaller components and add detail, reducing the manual process of adding edges and deleting faces.
Gizmos for each mesh appear in the Viewport to dynamically change the cut.
Similar to MshBool, the selection order matters as follows:
- The first selected mesh becomes the one you cut.
- The second selection becomes the cutting boundary.
MeshCut is a single-cut tool, meaning that you need to start a new session for each cut you want to make on the mesh.
Subdivide
The SubDiv (Subdivide) tool increases the resolution of a mesh by using its existing PolyGroups or triangles to create smooth surfaces. Subdivision is helpful in rapidly generating smooth surfaces to remove sharp edges. The iteration process of subdivision also makes it a valuable tool for creating levels of detail (LODs) for your mesh.
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| Subdivsion Level 0 | Subdivsion Level 2 | Subdivsion Level 5 |
Unlike other DCC software that use subdivision as a rendering tool, SubDiv applies subdivision directly to the mesh–altering the geometry.
You can set the number of subdivision iterations using the Subdivision Level property. The subdivision level will clamp once a max triangle count is reached.
How you subdivide your mesh is determined by the Subdivision Scheme.
| Subdivision Scheme | Description |
|---|---|
| Catmull Clark | PolyGroups are interpreted as polygons, and each polygon is subdivided into a number of quads based on the Subdivision Level. Newly generated vertices are placed on a smooth surface defined by the scheme, and existing polygon corners are also moved to this smooth surface. This scheme yields the best results if your input PolyGroups are mostly quads but can also handle some non-quad inputs. |
| Bilinear | Similar to Catmull-Clark in that it subdivides each PolyGroup. However, existing vertices are kept at the corners of the PolyGroups, and new vertex positions are linearly interpolated from the PolyGroup corners. If your input consists of planar PolyGroups, the output vertices will also lie on the planes defined by these PolyGroups. |
| Loop | Subdivides each triangle, ignoring PolyGroups. Each triangle is subdivided into more triangles based on the Subdivision Level. New and existing vertices are moved to a smooth surface defined by the scheme. |
The Subdivision Scheme will default to Loop if PolyGroups have fewer than three boundary edges.
To visualize where the SubDiv tool will subdivide your mesh, you can enable
- Render Groups, coloring the output PolyGroups.
- Render Cage, representing the polygon outline of the original mesh.
Enabling these settings helps visualize what the tool interprets as the input areas for subdivision. If your mesh is subdividing unexpectedly, you must check and adjust its PolyGroups.
You can also visualize where new polygons are generated by enabling New PolyGroups. Keeping this setting enabled when accepting the tool changes will assign the new PolyGroups to the mesh. After subdividing, you can adjust the normals and UVs computation.
To control the amount of smoothness applied to areas of your mesh or to keep parts of your mesh sharp you would add edges close together.
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| No Edge Loops | Edge Loops |
To continue learning about the various Modeling Mode tools see Modeling Tools.
