Bridge surface node

Skins trimmed surfaces or holes, creates highly controllable joins between arms and body, branches, or tube intersections.

All

Parameters

Example files

See also: Fillet, Join, Stitch, Skin

The Bridge SOP is similar to the Skin SOP but with much greater control over the resulting surface. Given a set of profiles (i.e. curves on surface) and/or spatial faces, the Bridge op builds a NURBS skin with specified tangent and curvature characteristics. The precision of the resulting surface is highly dependent on the number of required cross-sections and on the quality of the profile extraction. High precisions will generate a very dense surface with, potentially, many multiple knots.

In general, the higher the order of the curve, the better the fit the Bridge op will be able to provide. However, it is generally better to stick to cubics (order 4) curves, as the software is optimized for cubics.

Because the Bridge op can join both a set of spatial curves and trim curves, it can be used much like the Skin SOP and/or the Fillet SOP. However, bridging trimmed surfaces is more expensive than bridging carved surfaces.

You will usually need a Trim SOP, Bridge SOP, or Profile SOP after a Project SOP.

Use a Trim SOP to cut a hole in the projected surface.
Use a Bridge SOP to skin the profile curve to another profile curve.
Use a Profile SOP to extract the curve on surface or remap it’s position.

Note

To texture-map the resulting skin, use an Orthographic projection rather than a Spline-based projection. This results in better continuity across the surfaces.

Example: Joining Two Trim (Profile) Curves

Place a Circle SOP. Primitive Type: NURBS; Radius = 0.2, 0.2
Place a Grid SOP. Primitive Type: NURBS.
Feed both the Circle and Grid SOPs into a Project SOP. Make it the display SOP. You notice the projected circle on the grid: our trim curve.
Append a Trim SOP and make it the display SOP. Turn on Gouraud shading for the Viewport. You now see the trimmed holes in the surface of the grid.
Append a Copy SOP. Number of Copies: 2; Translation Z: 1.0; Rotation X: 30. Make it the display SOP. Now we have two grids with trimmed holes in them.
Append a Bridge SOP, and make it the display SOP. Scale Tangents: 0, 0, 0; Use Curvature: On; Preserve Curvature Magnitudes: Off; Scale Curvatures: 3, 3, 3 .
To specify which profile curves to skin, turn on Profile Numbers in the Viewport options, (click ((Plus)) at the bottom-right of Viewport, and enable the icon). We can see the profile numbers of the two trim curves are 0.0 and 1.0, meaning the 0th profile of the 0th primitive and the 0th profile of the 1st primitive). The strange numbering is because primitive numbers start at 0 instead of 1.
In the Bridge SOP’s Group field enter: *.0. This means to include the 0th (first) curve from all (the * wildcard character) primitives in the skin. You now see the resulting bridge between the two trim curves. The skin bulges outwards.
We can control the bulge by playing with the Scale Curvatures and the Tangent Magnitudes. Set the Scale Curvatures to: -3, -3, -3 . Now we have an inward-bulging tube connecting the two holes.
Experiment with moving the location and size of the holes (change the Translation and Radius in the Circle SOP). The Bridge SOP dynamically updates the geometry connecting the two surfaces. Setting the Scale Curvature to: 0, 0, 0 produces a straight-through connection between the two holes.

Parameters

Group	Subset of profiles and/or faces to bridge.
Bridge	Allows bridging of subgroups of N primitives or patterns of primitives.
N	Pattern of primitives to bridge.
Order	Spline order for both profile extraction and skin.

Surface Properties

Min X-sections

Minimum number of cross-sections in skin.

Use

Type of normal to use for computing direction.

Frenet Frame	This sets the local normal according the the frenet frame of the curve. This is the vector perpendicular to both the tangent of the curve and the binormal (the direction of curvature).
Normal	This uses the calculated normal of the entire curve as the normal.

Circular-Arc Fillet

Build the skin as a circular fillet, if possible.

Rotate/Scale Tangents

The scaling and rotation parameters contain three fields:

First Field	Applies to the first face in the input.
Second Field	Applies to all intermediate faces.
Third Field	Applies to the last face in the input.

Rotate Tangents

Further rotation of the tangents (degrees).

Scale Tangents

Further scaling of the tangents. When building a circular fillet, only the sign of the tangents is used.

Use Curvature

Take curvature into consideration as well.

Scale Curvatures

Further scaling of the curvature.

Profile Extraction

Overview	The parameters in this tab determine the precision with which to extract profile curves.
Divisions Per Span	Number of 2D points evaluated in each span.
Tolerance	Precision of 2D fitting algorithm.
Preserve Sharp Corners	Enables or disables fitting of sharp turns.

Example files

BridgeCurvesandPrims

$HFS/houdini/help/examples/nodes/sop/bridge/BridgeCurvesandPrims.cmd

Load | Launch

This contains two examples of how to use the Bridge SOP.

The first example illustrates how to use the Bridge SOP on projected and trimmed curves. The second illustrates how to use the Bridge SOP on two carved primitives.

Press Play to see an animated version of the Bridge over Two Carves.

Usages in other examples

Example name	Example for