Poly Extrude 2.0 geometry node

Extrudes polygonal faces and edges.

On this page	Overview How to Follow a curve Distance/twist vs. transform Multiple extrusions Splitting groups Notes Parameters Extrusion Front transform Output Geometry and Groups Insetting Normals Spine Control Shape Adjustment External Spine Thickness Twist Local Control Local Attributes Local Frames Examples
Since	14.5

Overview ¶

Poly Extrude lets you “pull” faces and edges out to create new columns/sheets of polygons.

You can make the extrusion bigger or smaller (inset/outset), and twist it.

If you extrude interior edges, the node will use the surface normals.

If you extrude boundary edges, the node will use the surface direction.

You can set the number of divisions in the extrusion and have the extrusion curve from the source to the destination.

You can draw a curve and have the extrusion follow the shape of the curve.

The node creates a copy of the selected components and transforms them according the parameters, then builds a polygonal bridge between them. The original components are called the back of the extrusion (drawn in red), and the copied/transformed components are called the front (drawn in green).

How to ¶

To...	Do this
Extrude edges/faces	Select the edges or faces you want to extrude. On the Model shelf, click the Poly Extrude tool. Use the line handle to pull or push the extrusion front. Use the controls in the operation toolbar across the top of the viewport to set the inset and number of divisions.

Follow a curve ¶

To...	Do this
Make the extrusion follow an external curve	Draw the curve you want the extrusion to follow. Extrude the edges/faces (see above). Connect the curve to the Poly Extrude node’s second input. In the Poly Extrude parameters, set Spine shape to “Curve from second input”.

Distance/twist vs. transform ¶

By default, the tool only extrudes along the normals, with controls for distance, inset, and twist.

You can optionally turn on the Transform extruded front to also apply a full move/rotate/scale transform to the extrusion front.

This transform is applied in addition to the Distance and Twist controls, so you probably want to set them to 0 if you want to use the transform.

Multiple extrusions ¶

The node automatically treats adjacent edges/faces as groups.

You can extrude individual edges/faces instead of treating them as a group.

The node transforms each element in its own space (unless you set Extrusion mode to “Translate Global”).

Splitting groups ¶

If you want to define multiple source loops with edges/faces that happen to be adjacent, they will just look like one thing to the node. You can choose a point/edge Split group that divides adjacent faces/edges into separate groups.

In this image, the yellow line is an edge group splitting the selected faces into two sources.

(If you are extruding edges, you split with a point group. If you are extruding faces, you split with an edge group.)

Notes ¶

Unlike previous versions of PolyExtrude, this node does not support local variables or per-primitive/edge expressions, for performance reasons.

If you want to vary some parameter per-primitive/edge, store the value in an attribute and use the controls on the Local Control tab.

Parameters ¶

Group

Faces or edges to extrude. This can be the name of a primitive or edge group.

Divide Into

Whether to treat adjacent edges/faces as a group, or as individuals.

Split Group

When Divide into is “Connected components”, any adjacent elements are treated as a single group. If there are edges/faces that are adjacent but you want to be separate groups, you can split them using this group. See splitting above.

Extrusion Mode

Which normals to use to extrude faces/edges.

Primitive/Edge Normal

Extrude faces along their normals, extrude edges intelligently depending on whether they are interior or boundary edges.

Point Normal

Extrude along point normals.

Distance

How far (in Houdini units) to “pull out” the extrusion. You can use a negative number to “push” the extrusion in the opposite direction of the normals.

Inset

Expands or dilates the extrusion front. This has no effect when extruding edges.

Twist

Twists the extrusion front around the extrusion spine.

Divisions

The number of rows of polygons in the extrusion.

Spine shape

The path the extrusion takes between the back and front.

Straight

Straight from the back to the front.

Curved

Curve between the back and front orientations.

Curve From Second Input

Take the shape of a curve connected to this node’s second input.

Extrusion ¶

Front transform ¶

Transform Extruded Front

Turn this on to show full transformation (move, rotate, scale) controls for the extrusion front. This transform is applied in addition to the Distance and Twist controls, so you probably want to set them to 0 if you want to use the transform.

Transformation Order

Order in which to apply local transformation (when Transform Extruded Front is on).

Rotation Order

Order in which to apply local rotations (when Transform Extruded Front is on).

Translate

Moves the extrusion front (when Transform Extruded Front is on). The Z component controls the extrusion amount. The X and Y are applied to the front after extrusion.

Rotate

Rotates the extrusion front (when Transform Extruded Front is on). You can use this to twist the extrusion, but see also Twist parameter for more information.

Scale

Scales the extrusion front (when Transform Extruded Front is on).

Shear

Shears the extrusion front (when Transform Extruded Front is on). The numbers represent X shear in XY plane, X shear in the XZ plane, and Y shear in the YZ plane.

Pivot

Local pivot point for moving, rotating, and scaling the extrusion front (when Transform Extruded Front is on). This is local to each front, unless Extrusion mode is “Global translate”.

Output Geometry and Groups ¶

Output Front

Generate polygons for the extrusion front. Turn this off if you only want the sides. This has no effect when extruding edges.

Front Group

Enter the name to put the polygons of the extrusion front in this group. You can use this group name in later nodes to easily target just the front polygons.

Output Back

Turn this off to delete the original extruded polygons. This has no effect when extruding edges.

Back Group

Enter the name to put the polygons at the start of the extrusion in this group. You can use this group name in later nodes to easily target just the back polygons.

Output Side

Generate polygons for the sides of the extrusion. If you turn this off, the node essentially is just a copy and translate of the selected edges/faces.

Side Group

Enter the name to put the polygons in the extrusion sides in this group. You can use this group name in later nodes to easily target just the side polygons.

Front Boundary Group

Enter the name to put the edges bordering the front and side of the extrusion in this group. This group is equal to the front group when extruding edges. This group is empty when both Output Front and Output Side are off. This group is highlighted green in the polyextrude state in the viewport.

Back Boundary Group

Enter the name to put the edges bordering the back and side of the extrusion in this group. This group is equal to the back group when extruding edges. This group is highlighted red in the polyextrude state in the viewport.

Preserve Groups

If the original edges/faces were in any groups, add the corresponding edges/faces in the extrusion front to the same groups.

Insetting ¶

Limit insetting

When this is on, the extrusion front cannot be inset beyond a point where the node determines it would create a degenerate, pinched, zero-size, or otherwise undesirable front. If you turn this off, insetting can continue to shrink the front through pinching and then invert so that further insetting actually grows the front. You should generally just leave this on all the time.

Use common limit

If you are extruding multiple fronts, as you increase Inset, once one front has a zero-size edge, all fronts stop shrinking. Turn this off to allow each front to shrink to zero individually as you increase Inset. If Limit insetting to zero size is off, this option is ignored.

Normals ¶

By default, if the input geometry has normal attributes, the node adds those attributes to the extruded geometry.

Add Vertex Normals

Add vertex normals. If vertex normals existed on the original selected edges/faces, the node overwrites them.

Cusp Angle

Vertices across a shared edge will have different normals if the face normals differ by more than this angle.

Cusp All Front Boundary Edges

Always cusp boundary edges of the extrusion front, ignoring the Cusp angle.

Cusp All Back Boundary Edges

Always cusp boundary edges of the extrusion back, ignoring the Cusp angle.

Spine Control ¶

Bridging tab controls several details of how the bridge connecting the back and front behaves.

Shape Adjustment ¶

Front Magnitude

How much the orientation of the front affects the direction of the extrusion at that end. Only available when Spine shape is not “Straight”.

Back Magnitude

How much the orientation of the original edges/faces affects the direction of the extrusion at that end. Only available when Spine shape is not “Straight”.

Front Stiffness

How far the extrusion path follows the orientation of the extrusion front. Only available when Spine shape is not “Straight”.

Back Stiffness

How far the path of the extrusion follows the orientation of the original edges/faces. Only available when Spine shape is not “Straight”.

Interpolation

A technical parameter of the node’s internal algorithm. “Rotating frame” tends to be better for twisting bridges, but in practice there’s no good basis for choosing one or the other. You can try both and see if they make a difference for your bridge.

Spacing

Controls the spacing of the divisions along the bridge.

Uniform

Spaced equally.

Curvature Sensitive

Uses more polygons in high curvature areas and fewer polygons in straight areas.

External Spine ¶

Available when Spine shape is “Curve from second input” and the node’s second input is connected.

Reverse Direction

Reverse the direction of the spine curve.

Axial Rotation

Rotate the spine curve around the line through its end points.

Front Blend

How much to blend the direction at the end of the curve with the orientation of the extrusion front.

Back Blend

How much to blend the direction at the start of the curve with the orientation of the original edges/faces.

Thickness ¶

These parameters let you scale the width of the bridge along its length, creating pinches and/bulges in the bridge.

Thickness Scale

Scales the values of the Thickness ramp and/or Thickness attribute.

Thickness Attribute

If Spine Shape is “Curve From Second Input” (on the Spine tab), use this attribute on the external curve to control the thickness of the bridge. This is multiplied by the Thickness scale and added to the thickness ramp.

Thickness Ramp

Controls the thickness of the bridge along its length. The horizontal axis represents the length of the bridge. Values of 0.5 do no scaling. Values less than 0.5 narrow the bridge. Values greater than 0.5 widen the bridge.

Twist ¶

Twist Scale

Scales the values of the Twist ramp and/or Twist attribute.

Twist Attribute

If Spine Shape is “External” (on the Spine tab), use this attribute on the external curve to control the twist of the bridge. This is multiplied by the Twist scale and added to the twist ramp.

Local Twist Ramp

Controls the twist of the bridge along its length. The horizontal axis represents the length of the bridge. Values of 0.5 represent no twist. Values less than 0.5 twist in one direction, values greater than 0.5 twist in the other direction.

Local Control ¶

Local Attributes ¶

Distance scale

Multiply the extrusion distance by the value of this attribute (primitive attribute for face extrusion or point attribute for edge extrusion).

Inset scale

Multiply the inset amount by the value of this attribute (primitive attribute for face extrusion or point attribute for edge extrusion).

Twist scale

Multiply the twist amount by the value of this attribute (primitive attribute for face extrusion or point attribute for edge extrusion).

Divisions scale

Multiply the number of divisions by the value of this attribute (primitive attribute for face extrusion or point attribute for edge extrusion).

Local Frames ¶

You can use these attributes to control the local transform space and extrusion amount of each individual component.

If you're extruding faces, these should be primitive attributes, and the values are averaged from all faces in an extrusion front. If you're extruding edges, they should be point attributes, and the value of each edge is the average of the values on its two endpoints.

X Direction

Use this vector attribute (primitive attribute for face extrusion or point attribute for edge extrusion) as an edge/face’s local X axis. The node makes this orthogonal to the local Z axis if it’s not already. If the vector is 0,0,0 the node ignores it. The node automatically normalizes the vector.

Z Direction

Use this vector attribute (primitive attribute for face extrusion or point attribute for edge extrusion) as an edge/face’s local Z axis. This overrides the computed normal. If the vector is 0,0,0 the node ignores it. The node automatically normalizes the vector.

Center

Use this vector attribute (primitive attribute for face extrusion or point attribute for edge extrusion) as the edge/face’s center. This overrides the computed centroid.

Z Scale

Scale the extrusion amount by the value of this attribute.

Examples ¶

PolyextrudeTube Example for Poly Extrude geometry node

This example demonstrates how to extrude geometry using the Poly Extrude SOP, as well as demonstrating the different extrude controls, Global and Local.