Houdini 20.5 Nodes Geometry nodes

Carve geometry node

Slices, cuts or extracts points or cross-sections from a primitive.

On this page

The Carve op works with any face or surface type, be that polygon, Bezier, or NURBS. It can be used to slice a primitive, cut it into multiple sections, or extract points or cross-sections from it.

Like the Project SOP, it also creates profile curves, but they are extracted as iso-parametric (2D) profiles directly from a surface, whereas the Project SOP extracts a 3D curve projected onto a surface.

Note

When using a Carve op on a trimmed surface, you can’t fillet or join the trim curves.

Using Carve

  1. Select the faces or hulls to carve.

  2. Click the Carve tool on the Model tab.

  3. Specify what to slice, cut, or extract using the parameter editor.

Tips

Opening a Closed Primitive

Given a closed surface, it can be converted to an identical open surface at any location by using the Carve op, and cutting at a single location (e.g. First U enabled, Second U disabled). The same is true for faces.

Dicing a Face or Surface

Select the Cut operation, First U = 0, Second U = 1, First V = 0, Second V = 1, with (at least) three divisions for U and V. This will dice the surface into (at least) 3 x 3 components. This can later be used with the Primitive SOP to “explode” the surface.

Cutting a Hole in a Surface

Select the Cut operation, First U = 0.33, Second U = 0.66, First V = 0.33, Second V = 0.66, 2 divisions for U and V. Keep Inside is off, Keep Outside is on. This will cut a rectangular region from the center of the surface.

Animating a Point Over a Face or Surface

Select the Extract option, First U = x, Last U disabled, First V = y, Last V disabled, Extract Point is on, Keep Primitives is optional. This will create a point over any position on the surface (0<=x<=1, 0<=y<=1).

Parameters

Group

Specifies a subset of primitives to carve.

Carve Curves by Relative Arc Length

Curves have a parameterization that does not match the actual distance along the curve. A carve of 0.5 will not be half way along the curve, but half way along its parameterization. Turning this on will solve for the actual location half way along the curve as measured by distance.

Note this has no effect on two dimensional surfaces as the arc length is not well defined.

First U

Starting location in the U direction.

First U Attrib

A primitive attribute to replace or scale the first U location with.

Second U

Ending location for the operation.

Second U Attrib

A primitive attribute to replace or scale the second U location with.

U Divisions

Number of cuts/extracts to be performed.

Cut At All Internal U Breakpoints

Cut only at ends or along all internal breakpoints. Only At Breakpoints must be toggled.

First V

Starting location in the V direction.

First V Attrib

A primitive attribute to replace or scale the first V location with.

Second V

Ending location for the operation.

Second V Attrib

A primitive attribute to replace or scale the second V location with.

V Divisions

Number of cuts/extracts to be performed.

Cut At All Internal V Breakpoints

Cut only at ends or along all internal breakpoints. Only At Breakpoints must be toggled.

Cut

Splits primitive at locations specified above.

Keep Inside

Keeps the primitives between First and Second U.

Keep Outside

Keeps the primitives outside First and Second U.

Extract

Extracts points, cross-sections, or curves-on-surface along each location specified above. Only points can be extracted from a face and the V parameter has no effect. Extraction of cross-sections and curves-on surface is possible only if the primitive is a surface.

Keep Original

Will keep the original primitive from being removed.

Only At Breakpoints

Perform the operation only at breakpoints for NURBS and Bezier surfaces or faces and at vertices for polygonal faces and surfaces.

Examples

CarveExtractCurve Example for Carve geometry node

This network is a demonstration of how the Carve SOP can be used to extract various elements of the surface geometry.

Depending on the type of geometry, the Carve SOP may be used to extract points from polygonal objects or curves from NURBS surfaces.

Furthermore, the Carve SOP uses the surface U and V information to extract the various elements, and by animating the U and V values we can create various effects as the points and curves move on the geometry surface.

CopySpikes Example for Carve geometry node

This network contains an example of how the Carve SOP can extract 3D Isoparametric Curves from a surface, and how those curves may be used as a copy template.

The Carve SOP can be used to slice a primitive, cut it into multiple sections, or extract points or cross-sections from it.

In this example, the Extract option has been used to Extract 3D Isoparametric Curve(s). A series of disk-like shapes are created as the Carve SOP extracts curves from points around the surface with the same V Directional value.

It then uses the points along those curves as a template on which to copy sourced geometry.

DiscCarve Example for Carve geometry node

This network is a demonstration of the Carve SOP, specifically when dealing with extracting curves from a NURBs surface and animating that extraction.

The Carve SOP uses the U and V surface data to carve the geometry.

In our example we have extracted curves which can then be used as basis for other geometry to create interesting effects.

Given the Carve SOP uses a 0 to 1 value to carve either in the U or V surface direction, that value can be animated either by keyframing or through expressions.

See also

Geometry nodes