Houdini 20.5 Nodes Geometry nodes

TopoBuild geometry node

Lets you interactively draw a reduced quad mesh automatically snapped to existing geometry.

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Since 15.0

Overview

This node is useful when you have a very high-resolution model and want to create a much lower-resolution model from it. You can draw the quads of the new mesh by hand, automatically snapping the corners to the existing surface.

(3D model by Artec Group inc.)

PolyDraw shelf tool

Draw out polygons using the topobuild tools, without a reference surface.

Toolbar

When this node is active, the operation toolbar across the top of the 3D view has controls that change the way the tool works in the viewport. See How to use the node below for more information.

Build ⇧ Shift + 1

Switch to the Build sub-tool. This lets you create and edit polygons by placing points on the reference surface.

Slide ⇧ Shift + 2

Switch to the Slide sub-tool. This moves points/edges in the new surface across the reference surface.

Cut ⇧ Shift + 3

Switch to the Cut sub-tool. This lets you cut through polygons by drawing lines.

Brush ⇧ Shift + 4

Switch to the Brush sub-tool. This lets you move points by brushing over them.

Smooth ⇧ Shift + 5

Switch to the Smooth sub-tool. This lets you relax points by brushing over them.

Skin ⇧ Shift + 6

Switch to the Skin sub-tool. Build “sleeves” of polygons by defining profile curves and a seam.

Slide mode

When using the Slide sub-tool, you can set this to control how to slide edges between adjacent rows/columns.

Anchored blend

Blends the original shape of the edge selection with an interpolation between the adjacent edges.

Blend

Only blends between the shapes of the adjacent edges, doesn’t retain the original shape of the edge selection at all.

Match Profile

Maintains a fixed distance from one of the adjacent edges.

Match Opposite Profile

Same as “Match Profile” but maintains a fixed distance from the other adjacent edge.

Uniform Distance

Moves the edge selection a fixed distance from its original position, without regard to adjacent edges.

Opacity

Changes how much brushing affects the points.

Smooth All

When using the Smooth sub-tool, click this to smooth all points.

Edge snap

When using the Cut sub-tool, snap to existing edges. This makes it easier to cut across polygons.

Divisions/Spans

When using the Skin sub-tool, controls how many rows and columns to add between cross-sections.

How to

To...Do this

Start using the tool

  1. Select the geometry you want to use as the template.

  2. On the Model shelf, click Topo Build.

    The tool creates a new Geometry object for the new surface. It imports the selected surface into the new object.

  3. Click four points on the template surface to create the first face.

Set up the viewport

  • You can use a visualizer to color the original surface to make it easier to distinguish the new surface.

  • Change your shading mode to Hidden Line Ghost to get a better view of the new surface.

  • Hide the construction plane to get a better view of the new surface’s edges.

Build

To...Do this

Draw new quads

  1. Click an existing point to start drawing a new quad.

  2. Click the other three corners to finish the new quad.

    Drawing automatically snaps to existing points.

Extend edges

  • Click an edge to start creating new faces from the edge.

  • You can click multiple times to create a strip of new quads.

  • You can B-drag to scale or G-drag to rotate the edges before you click to place them.

  • Press ⎋ Esc or click to stop adding.

Create free points to snap to

Click outside existing quads.

Select points/edges

  • To select a free point, click it.

  • To select a point that’s part of a quad, click it and then press ⎋ Esc to cancel drawing.

  • To select an edge, click it and then press ⎋ Esc to cancel extending. You can use edge loop selection.

  • To select additional points/edges, hold ⇧ Shift and click them.

Move existing points/edges

  • Drag existing points or edges to move them across the template surface.

  • You can drag points onto other points to fuse them.

Temporarily disable snapping

Hold ⌃ Ctrl and click to disable automatically snapping to existing points.

Delete all free points

Press ⇧ Shift + ⌦ Del.
Collapse to point ⇧ Shift + X

Replaces the selected faces or edges with a single point (in Topobuild tool’s Build mode).

Make circle ⇧ Shift + C

Bends the outer edges of the selection into a circle.

Space out selection ⇧ Shift + E

Tries to move the selected edges to be spaced equally apart (in Topobuild tool’s Build mode).

Straighten selection ⇧ Shift + S

Tries to adjust the selected edge to be straight (in Topobuild tool’s Build mode).

Slide

The slide sub-tool is similar to the slide mode in the Edit node. It lets you select and slide edge columns/rows across the reference surface.

Use the Slide Mode menu to control how the sliding edges interact with the adjacent edges.

Cut

To...Do this

Split existing polygons

  1. Select the Cut sub-tool.

  2. Click a point or an edge to start the cut.

    You can use the Edge division controls in the toolbar to set up snapping points along edges. You can increase or decrease the number of snapping points using the mouse wheel.

  3. Move the mouse to draw the line to cut.

    You can cut across multiple polygons at once.

  4. Click to cut, or press ⎋ Esc to cancel.

    You don’t have to click a point or edge to cut. If you click off an edge, the tool make any valid (yellow) cuts along the line and ignore invalid (magenta) cuts.

Insert edge loops

  1. Select the Cut sub-tool.

  2. Hold ⇧ Shift and click an edge.

    You can use the Edge division controls in the toolbar or the mouse wheel to change the number of edge loops inserted.

Inserting edge loops only works on quads. The tool will ignore polygons with more or less than four sides.

Brush and Smooth

  • Drag ⇧ Shift + to change the size of the brush.

  • Use the Opacity setting in the toolbar to control how much the brush affects the points.

To...Do this

Brush points across the surface

  1. Select the Brush sub-tool.

  2. Brush across points to move them. The points stay on the reference surface as they move.

Smooth point positions by brushing

  1. Select the Smooth sub-tool.

  2. Brush across points to relax their positions. The points stay on the reference surface as they move.

Smooth all point positions

  1. Select the Smooth sub-tool.

  2. Press the Smooth All button in the toolbar. The points stay on the reference surface as they move.

Use the Opacity setting in the toolbar to control how much the operation affects the points.

Skin

This sub-tool is useful for building quasi-cylindrical features around the reference surface, for example around a dinosaur’s tail. This tool does not support areas with holes.

To...Do this

Build a polygon “sleeve” around the reference surface

  1. Select the Skin sub-tool.

  2. Position the view so you're looking at the reference surface side-on.

  3. Drag to draw “cross-section” lines across the feature. The tool will turn these into edge loops in the generated surface.

    While creating cross-sections you can select and edit cross-sections you've already drawn:

    • Hold ⇧ Shift and box-select one or more cross-sections.

    • Press ⌦ Del to clear the selected cross-section(s).

    • Hold B and drag to move the selected cross-section(s) along the reference surface.

    • Press ⇧ Shift + A to align the selected cross-section(s) with the reference geometry.

  4. To generate a surface, hold ⌃ Ctrl and drag across the cross-sections (for example, along the length of the tail) to define the “spine” of the feature. The tool uses this free-form line to create a seam along the generated surface.

    Tip

    If you drag across an unshared edge before the first cross-section, the tool will start the new skinned surface from the unshared edge.

    • You can continue to add and edit the cross sections after drawing the seam and generating the surface.

    • To change the intersection point of the seam with a cross-section, hold ⌃ Ctrl and drag over just that cross section again at a different point.

  5. Use the Spans option in the operations toolbar (at the top of the viewer), or roll to set the number of divisions around the sleeve.

  6. Press Enter, or select another tool to finish editing the sleeve surface.

    Once you exit the Skin sub-tool, you can no longer go back and edit the cross-sections or seam. You can use the other tools to edit the generated polygons, or undo to get back to the editing mode.
Align cross sections ⇧ Shift + A

Align any selected cross-sections perpendicular to the seam (in Topobuild tool’s Skin mode).

Translate cross sections ⇧ Shift + B

Hold this key and drag to move selected cross-sections while using the Skin mode.

Parameters

Number of Edits

As you work, the node records the edits you make in these parameters.

Commit Edits

Saves the current edits and resets the parameters to start new edits.

Reset All Edits

Restores the geometry to its initial state.

Inputs

Mesh Geometry

Quad-mesh geometry from a previous operation. If provided, TopoBuild will continue to build upon this mesh geometry.

Template Geometry

The source geometry to re-topologize. The points of the quad mesh will snap to the surface of this geometry.

Geometry nodes