Selection Types

This selection operation converts a component selection from the given type to another component type, polygon, edge, or vertex, which is used by a procedural mesh operator in down stream in the Mesh Operations list (stack). The original source selection is retained and new selections are added.

Example

1.

Add a Sphere to your scene.

2.

Under the layout menu, click Polygons, and select four polygons on the Sphere.

3.

On the top left of the menu, beside the Work Plane button, click the Selection Sets icon and then click New set.

4.

Name this selection set Polys and click OK.

5.

On the right panel, open the Mesh Ops tab, click Add Operator, and double-click Mesh Operations > Edge > Edge Bevel.

6.

Drag the handles to apply a bevel on the edges.

7.

On the Mesh Ops tab, expand Edge Bevel > Selection, and click (Add Selection).

8.

Double-click Mesh Operations > Selection > Select By Selection Set.

The beveled edges are no longer displayed because the Select By Selection Set uses a polygon selection but the Edge Bevel needs an edge selection to work.

9.

In the Name field, enter Polys.

10.

Under Edge Bevel > Selection, click (Add Selection).

11.

Double-click Mesh Operation > Selection > Convert and ensure the Convert From option is set to Polygon.

The Edge Bevel is now applied to only the Polys selection set.

Convert Properties

Enable	Enables or disables the Select by Previous Operation function.
Invert	Inverts a single selection operation or all selected operations in the Mesh Operations list.
Blend Mode	Specifies the type of blend to apply. • Override - The default behavior. The current selection overrides all selection operations below it in the Mesh Operations list. Previous selections are discarded and the new selection is used instead. • Add - Adds a new selection to the previous selection. Elements are treated as de-selected if they are de-selected by all selection operations in the Mesh Operations list. • Subtract - Removes any elements that are selected by the selection operation from the previous selection. • Multiply - Only selects elements from the new selection operation that are also selected by the first, filtering the previous selection.
Convert From	Specifies the component selection mode: Polygons, Edges, or Vertices.

This selection operation marks elements around the boundary of a geometry for edits.

The image below shows a Polygon Bevel operation applied only to the border polygons of a plane, using the Select By Border selection operation:

When using this selection operation, selection is defined by a falloff item, which you can also add through the Mesh Operations list. The added falloff item defines which parts of the mesh get selected. You can edit the properties of the falloff item to modify the selection.

The falloff is evaluated to calculate a weight for each element, based on its world space position. If the weight is above a certain threshold, the corresponding element gets selected. The image below shows the Polygon Bevel operation applied to a region of a cube affected by Linear Falloff:

To specify a falloff:

1.

After adding the Select By Falloff operation, expand it in the Mesh Operations list to reveal its Falloff input.

2.

Click (Add Falloff) to specify a falloff type for the selection operation.

3.

In the Preset Browser, under New, double-click a falloff type.

The falloff appears in the list, and you can customize it in its Properties panel below the Mesh Operations list.

In the Schematic view, the selection operation item has a single graph input, allowing falloff items to be connected:

Select by Falloff Properties

The following options are available for this selection operation:

• Threshold - Determines whether a specific weight is treated as selected or not. Weights above the specified threshold get selected. For example, if the threshold is 50%, and the evaluated weight for an element is 40%, the element doesn't get selected. However, if the evaluated weight is 60%, it is selected.

This selection node allows you to define a selection using the element index in a list of indices. Each mesh element is given an index between zero and the total number of elements in the mesh. If a matching number is found in the index list, the element is selected. The list of indices are automatically populated with the current element selection when the selection operation is created.

Note:  As the input mesh changes, the index mapping may change, and the selected elements may be exchanged for other elements.

To define a selection using this operation, select elements of a mesh directly in the 3D viewport, and then add a compatible mesh operation. For example, select some polygons on a mesh, then add a Polygon Bevel tool in the Mesh Operations list. The Select By Index operation is automatically added to the operation's Selection input. The mesh operation then uses the selection you defined in the 3D viewport.

Select by Index Properties

You can modify or clear your selection by clicking the Select By Index node in the Mesh Operations list. This opens the operation's properties in the Properties panel. Here you have the following options:

• Selection - Allows ranges of elements to be defined. For example, if the range is 0-9, the first ten elements are selected. If the range is 0,1,2, the first three elements get selected. You can also combine selection, for example, you can enter 0-9,12,14,16,18-30.

• Set - Clears the existing selection and uses the newly-selected polygons instead.

• Clear - Removes all selections.

• Add - Adds the newly-selected elements to the existing selection.

• Remove - Removes the newly-added selection.

The Mesh Operation, Select By Polygon Tag, allows you to procedurally select polygons using a polygon tag to quickly locate any polygons that have a matching value. This is useful when you want to apply procedural operations to your polygon selection sets. For example, if you have modeled a table and you want to assign different colors to the legs and to the table top. The Select by Polygon Tag mesh operation allows you to quickly do that. You can specify your selection operation to be a Material, Part, or Selection Set. You can also enter any four characters in the Value field to select by arbitrary polygon tag type previously set up.

For more information about how to set up Material, Part, or Selection Set options, see Defining Shaders and Using Selection Sets.

Video:  Watch this video for an overview.
- Select by Material Tag

In the following example, we have previously modeled a table. This model has one mesh item and is procedural generated with Using Selection Sets created for the top and legs of the table.

To apply the Select by Polygon Tag:

1.

Download the following model. Alternatively, create your own model and assign selection sets. For more information, see Assigning a Selection Set.

2.

From the Mesh Ops tab, select an Assign Selection Set to apply a mesh operation. In this example, select Assign Selection Set - Table Legs.

3.

Click Add Operator, expand Mesh Operations > Polygon and double-click Material Tag.

The Material Tag Properties displays in the right panel. For more information, see Assigning Material Tags.

4.

In the Material Name field, type Legs, and then press Return.

The entire table displays in red.

Note:  Use the same capitalization for the created shader. To verify, open the Shading tab.

5.

In the Mesh Ops tab, expand Material Tag > Selection, and click Add Selection.

The Add Operation dialog displays.

6.

Expand Mesh Operations > Selection and double-click Select By Polygon Tag.

7.

Choose the polygon tag you want to use. In this example, select Selection Set from the Name dropdown menu.

8.

Select Legs from the Value dropdown menu.

Tip:  Alternatively, you can type in the Value field. This can be four characters used by the name of the polygon tag. For example, if you had four selection sets that started with the word Leg, all polygons from all four selection sets are selected in your scene. Once done, a material is assigned to all four legs.

9.

Click Return to view an update in the 3D viewport. Alternatively, click in the 3D viewport and press the space bar to drop your selection.

10.

From the Mesh Ops tab, select an Assign Selection Set to apply a mesh operation. In this example, select Assign Selection Set - Table Top.

11.

Click Add Operator, expand Mesh Operations > Polygon, and double-click Material Tag.

12.

In the Material Name field, type Top.

13.

In the Mesh Ops tab, expand Material Tag(2) > Selection, and click Add Selection.

The Add Operation dialog displays.

14.

Expand Mesh Operations > Selection and double-click Select By Polygon Tag.

The top of the table top has a newly assigned material.

Select by Polygon Tag Properties

The following options are available for this selection node:

• Name - Allows you to choose the polygon tag type. The following options are available:

• Material - Uses a previously created Material Tag

Tip:  A Material Tag creates a mask for the surfacing using the material and shading properties and applies them to specific surfaces. For more information, see Assigning Material Tags.

• Part - Uses a previously created Part Tag.

Tip:  A Part Tag works in a similar fashion to Material Tags, offering an additional means of defining polygon groupings. For more information, see Defining Shaders.

• Selection Set - Uses a previously created component and item-based selection set. For more information, see Using Selection Sets.

• Value - Specifies which tag to match to.

Use this mesh operation to query previous operations in the Mesh Operations list and specify groups of named elements to apply them to. This is done by selecting an element from the Mesh Operation list. Elements can also exist in more than one group, allowing an operation to provide groups for a subset of elements, as well as a group for all elements it has created. The Select by Previous Operation works with a number of procedural mesh operations and you can add support for more mesh operations when you create them.

Note:  Procedural operation options vary from one Mesh Operation to another. For example, a Bevel operation may provide separate lists for the back, side, and top polygons, whereas a Curve Fill operation may present different lists for each filled shape.

The following mesh operations are supported for the Select By Previous Operation:

• Axis Slice

• Booleans

• Curve Fill

• Curve Slice

• Edge Bevel

• Edge Extrude

• Polygon Bevel

• Polygon Extrude

• Slice

• Smooth Shift

• Solid Drill

• Sweep Effector

• Vertex Bevel

• Vertex Extrude

Video:  Watch this video for an overview.
- Select By Previous Operation

Select By Previous Operation Properties

The following options are available:

Option	Description
Enable	Enables or disables the Select by Previous Operation function.
Invert	Inverts a single selection operation or all selected operations in the Mesh Operations list.
Blend Mode	Affects the blending between different layers of the same effect type. The following options are available: • Override - The default behavior. The current selection overrides all selection operations below it in the Mesh Operations list. Previous selections are discarded and the new selection is used instead. • Add - Adds a new selection to the previous selection. Elements are treated as de-selected if they are de-selected by all selection operations in the Mesh Operations list. • Subtract - Removes any elements that are selected by the selection operation from the previous selection. • Multiply - Only selects elements from the new selection operation that are also selected by the first, filtering the previous selection.
Source Item	Specifies the Mesh Operation source item to apply the Select by Previous Operation to.
Name	Specifies the filter to apply to selected the Mesh Operation. The following options are available for the Booleans, Slice, Axis Drill, Solid Drill, and Curve Slice tools. Note:  The options available vary depending on the tool used. • Intersecting Edges - Sets the new intersecting edges and applies them to all of the above Mesh Operators in the Mesh Operations List. • Polygons from Geometry - Sets all polygons from the mesh connected to Geometry node. • Polygons from Driver Surface - Sets new polygons that are from the surface connected to a Driver Surface node used by the Boolean tool. • Stencil Polygons - Sets stencil polygons in Stencil mode for the Axis Drill, Solid Drill, and Boolean. This also sets drilled polygons while in Slice mode for the Axis Drill. • Cap Sections - This is used with the Slice tool when the Split option is enabled. This sets new polygons to fill the split section.

Click on the following images to view an animation, which demonstrates how the Select By Previous Operation is used to query previous operations in the Mesh Operations list.

The first animation demonstrates a Cylinder in a scene and a Slice Mesh Operation with both the Split and Caps Sections options enabled. In addition, an Edge Bevel is added to the top of the Mesh Operation list. It has the Selection option set to use Select by Previous Operation with the Source Item set to Boolean and Name set to Intersecting Edges. As a result, new polygons fill the split sections.

The following animation demonstrates a Cube and a Boolean Mesh Operation with the Operation option set to Union. In addition, an Edge Bevel Mesh Operation is added to the top of the Mesh Operation list. It has the Selection option set to use Select by Previous Operation with the Source Item set to Boolean and Name set to Intersecting Edges. As a result, the polygons that are from the surface connect to a Driver Surface.

Workflow Example

The following example walks you through the process of creating a model and applying the mesh operation Select by Previous Operation.

Adding Procedural Mesh Items

Add a number of procedural mesh items to your scene.

1.

In the Model layout, open the Mesh Ops tab on the right pane.

2.

In the Mesh Operations list, select the parent Mesh and then click Add Operator, expand Mesh Operations > Create, and double-click Circle.

3.

Select the parent Mesh again and then click Add Operator, expand Mesh Operations > Create, and double-click Rectangle.

4.

Position the Rectangle mesh operation item beside the Circle.

Adding Curve Fill and Thicken Mesh Operations

Add a couple of mesh operations to your mesh items.

1.

In the Mesh Operations list, select the parent Mesh item.

2.

Click Add Operator, expand Mesh Operations > Curves, and double-click Curve Fill. By default ,this mesh operation is set to 10 fill steps.

3.

In the Mesh Operations list, select the parent Mesh item.

4.

Click Add Operator, expand Mesh Operations > Polygons, and double-click Thicken. The tool handles are displayed in the viewport.

5.

Pull the tool handles to adjust the thickness. Both items in the scene change.

Tip:  You can also adjust the Offset field in the Properties panel to adjust the thickness.

6.

With Thicken selected In the Mesh Operations list, expand Selection, click Add Selection, and double-click Select by Previous Operation. The thickness of both shapes flattens to the original form.

7.

In the Properties panel, open the Select by Previous Operations tab, set Source Item to Curve Fill and Name to Shape 2. The Thicken previously applied, is applied to the Rectangle only.

8.

Select Thicken in the Mesh Operations list and pull the handles to change the thickness of the Rectangle.

9.

Select Curve Fill in the Mesh Operations list and update Fill Steps to 20. The polygon count increases for both the Circle and Rectangle but Modo still knows which polygons we intended to work on originally.

10.

Click the parent Mesh item in the Mesh Operations list, click Add Operator, expand Edge, and then double-click Edge Bevel.

11.

Expand Edge Bevel in the Mesh Operations list to view Selection, click Add Selection, and double-click Select by Previous Operation.

12.

In the Properties panel, set Source Item to Thicken and set Name to Front.

13.

Select the Edge Bevel mesh operation, expand Selection, and then click Add Selection.

14.

Double-click Boundary Edges.

Note:  The Boundary Edges mesh operation should be above the Select by Previous Operation. If it is not, click and drag it into place.

15.

Select the Edge Bevel mesh operation to display the tool handles. Move the handles to adjust the bevel edge of the Rectangle only. Notice, the Circle mesh item does not change.

Applying the Select by Previous Operation to another item in the scene

Apply these operations to the Circle in your scene.

1.

In the Mesh Operations list, expand Thicken > Selection and click Select by Previous Operation.

2.

In the Properties panel, change the Name value to Shape 1. The Circle is now displayed using the same result on a completely different input set.

With this operation, you can quickly locate connected geometry to a polygon, vertex, or edge selection. This Mesh Operation uses a previous selection method, such as Select By Index, to compute all vertices, edges, and polygons linked to the previous selection. This is useful if you have a complex model and you want to remove a selection from the parent mesh item.

The following example demonstrates applying Select Connected command to a previous selection method.

1.

On the top left corner of the interface, click the Preset Browser icon.

2.

On the left panel of the Preset Browser, expand Cloud Assets > Meshes > Interior, and double-click Afton_Stool.

3.

Under the layout menu, click Polygons.

4.

Select one polygon on the seat cushion.

5.

On the right panel, click Add Operator, double-click Mesh Operations > Edit > Delete.

The selected polygon is removed from the cushion.

6.

Expand the Delete mesh operation and click (Add Selection).

7.

In the Add Operations dialog, double-click Mesh Operation > Selection > Select Connected.

All of the polygons connected to the cushion are selected and deleted.

With this operation, you can define a selection using a range of indices matching the current element index. Each mesh element is given an index between zero and the total number of elements in the mesh. If the element index falls within the range defined by the selection operation, then the element is selected. You can also set up your selection to select, for example, every second or every third element in the range.

Note:  As the input mesh changes, the index mapping may change, and the selected elements may be different.

The image below shows a Polygon Bevel using the Select By Range operation. The Start index is 0, the End index is 80, and the Step value is 2.

Select by Range Properties

The following options are available for this selection node:

• Start - Specifies the first element in the range.

• End - Specifies the last element in the range.

• Step - Determines the step value over the range. For example, a value of 1 means that every value between the Start and End values is in the range, whereas a value of 2 means that every other value is in the range, and so on.

Use this selection operation to select all hard or soft edges on a geometry.

To learn how to create hard edges procedurally, see Procedural Hard Edges.

To use this selection type:

1.

Add the mesh operation you want to apply to the selection to the Mesh Operations list. In the Mesh Ops tab on the right panel, click Add Operator, then select the mesh operation.

In this example, we use an Edge Extrude operation.

2.

In the Mesh Operations list, Expand the Edge Extrude to reveal its Selection input. Expand Selection too, and click (Add Selection).

This opens the Add Mesh Operation dialog.

3.

Under Modifier Mesh Operations > New > Selection, double-click Select by Hard Edges.

The mesh operation's selection input is populated with the Select by Hard Edges operation. If you now start using the mesh operation, it will only affect the hard edges.

To select the soft edges of a mesh only:

1.

Select the Select by Hard Edges operation in the Mesh Operations list.

Its properties are displayed in the Properties tab in the lower right panel.

2.

Set Type to Soft.

Now the selection applies to all soft edges on your mesh.

Select by Hard Edges Properties

This selection type has the following properties.

Option	Description
Enable	Enables or disables Select by Hard Edges.
Invert	Inverts a single selection operation or all selected operations in the Mesh Operations list.
Blend Mode	Affects the blending between different layers of the same effect type. The following options are available: • Override - The default behavior. The current selection overrides all selection operations below it in the Mesh Operations list. Previous selections are discarded and the new selection is used instead. • Add - Adds a new selection to the previous selection. Elements are treated as deselected if they are deselected by all selection operations in the Mesh Operations list. • Subtract - Removes any elements that are selected by the selection operation from the previous selection. • Multiply - Only selects elements from the new selection operation that are also selected by the first, filtering the previous selection.
Type	Specifies whether the selection applies to Hard or Soft edges.

This selection operation marks any elements that exist within a specified selection set. Combined with the Assign Selection Set mesh operation, this allows selection to be stored and then later used further up in the Mesh Operations list. For details on assigning selection sets, see Selection Types.

Note:  The selection set should be defined first, before adding the operation you want to use it with. So the Assign Selection Set operation should be below the other operation in the Mesh Operations list.

Select by Selection Set

The following options are available for this selection node:

• Name - Specifies the name of the selection set to use.

Selection Operators are a special kind of selection operation that test the element selection using an external Modo rig with customizable rules.

On each selection operator, the information about the element is provided as an output channel. For example, on the Polygon Selection Operator, information such as the position, normal, area, and index is provided as a channel, and a single input channel called Selection allows the selection state to be driven by a rig.

You can build any kind of Modo rig to take the output values from the selection operators, and determine the input value, specifying whether selection should be performed. When the selection operator is evaluated, the rig is evaluated for each mesh element and a different selection state can be returned for each element.

The example below guides you through setting up a simple rig using a Polygon Selection Operator. A Polygon Bevel operation is applied to polygons on a toroid, but only the ones facing the camera are selected.

1.

Add a toroid to your scene from the Basic sub-tab of the Model toolbox, and subdivide it by pressing D on the keyboard for a more visible effect.

2.

Go to the Setup layout, select the camera item in your scene, and in the Schematic viewport, click Add Selected to add it to the viewport. Then drag its World Position channel to the Schematic from the Channels list on the right.

Note:  To make sure that the camera always faces the toroid, select your camera item and toroid, and in the camera's Properties, click Set Target.

3.

In the Mesh Operations list on right side of the interface, add a Polygon Bevel by clicking Add Operator, and under Mesh Operations > Polygon, double-clicking Polygon Bevel. Adjust the Shift amount by using the handles in the 3D viewport, or by editing the tool's Properties.

4.

Expand the Polygon Bevel operation in the list to reveal its Selection input, then click (Add Selection) and in the Preset Browser, click Selection Operator: Polygon.

This turns off the effect of the Polygon Bevel, as nothing is selected at this point.

5.

Add the Selection Operator to the Schematic viewport, then double-click its diamond connector to show the connected Polygon Bevel operation.

6.

Add the Selection Operator's Position X, Y, Z and Normal X, Y, Z channels to the Schematic by dragging them in from the Channels list.

At this stage, the Schematic viewport looks like this:

Now that we've added the camera, the Polygon Bevel, and the Selection Operator, we have to calculate the angle from the geometry to the camera.

1.

In the Schematic, add two Matrix Constructs by clicking Add... at the top of the viewport, then under Channel Modifiers > Matrix, double-click Matrix Construct.

2.

Add the Vector Maths:Add node, then connect the Position and Normal channels of the Selection Operator to the Vector A and Vector B channels of the Add vector respectively, to add them together.

You have the following connections in the Schematic now:

3.

Connect the Add node's Output to the first Matrix Construct's Input, then connect the Selection Operator's Position channel to the other Matrix Construct's Input.

4.

Add a Measure Angle channel modifier to the Schematic, and make the following connections:

• First Matrix Construct's Output channel to Measure Angle's Position to A.

• Second Matrix Construct's Output channel to Measure Angle's Position From.

• Camera's World Position channel to Position to B.

The Schematic at this point looks like this:

Next, we add a conditional node that we can use to select polygons which have an angle of less than, say, 45 degrees.

1.

Optional: To be able to drive the selection, and to make the connections a bit clearer: separate the Selection Operator's Select channel by right-clicking on it and clicking Separate Channel.

2.

Click Add... at the top of the Schematic viewport, and under Channel Modifiers > Conditional, double-click Logic:A is less than B.

3.

Connect the Measure Angle's Angle Output to the conditional node's Value A channel, and connect the conditional node's Result Channel to the Selection Operator's Select channel.

4.

Select the A is less than B conditional node, and in the Channels list on the right side of the interface, set Value B to 45.

Modo now bevels the polygons that are facing the camera. As you move the camera around, or change the angle value, the affected area changes.

The images below final result in the 3D viewport and the corresponding Schematic:

Selection Operator Channels

Name	Type	Description	Minimum	Maximum
Selection Operator: Edge
Index	Integer	The index of the edge in the mesh.	0
Position	Vector XYZ	The edge position.
Normal	Vector XYZ	The edge normal.
Length	Distance	The distance from one vertex on the edge to the other.	0.0
Angle	Angle	The angle between the two polygons connected to the edge.	0.0	360.0
Is Border	Boolean	Outputs true if the edge is on the boundary of a polygon island.	False	True
Vertex A	Vector XYZ	Provides the position of the first vertex in the edge.
Vertex B	Vector XYZ	Provides the position of the second vertex in the edge.
Selection Operator: Polygon
Index	Integer	The index of the polygon in the mesh.	0
Position	Vector XYZ	The centroid position of the polygon.
Normal	Vector XYZ	The polygon normal.
Area	Distance	The area of the polygon.	0.0
Flatness	Percent	The polygon flatness, determined by how coplanar a polygon is.	0.0	1.0
Vertex Count	Integer	Outputs the number of vertices that define the polygon.	2
Is Border	Boolean	Outputs true if the polygon is on the boundary of a polygon island.	False	True
Selection Operator: Vertex
Index	Integer	The index of the vertex in the mesh.	0
Position	Vector XYZ	The vertex position.
Normal	Vector XYZ	The vertex normal.
Edge Count	Integer	The number of edges connected to this vertex.	0
Is Border	Boolean	Outputs true if the vertex is on the boundary of a polygon island.	False	True
Select	Boolean	Specifies whether the mesh element should be selected or not.	False	True