Loft

Toolbar Menu

Surface Creation
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Surface

Loft

 History enabled

 Crease splitting enabled

The Loft command fits a surface through selected profile curves that define the surface shape.

Steps

To drag seams (closed cross-section curves only)

  1. Select a seam point marker, and move it along the closed curve.
  2. Continue to adjust the seam points until they line with each other and the closed curves all have the same direction, and then press Enter.

Adjust seam options

Flip

Reverses the curve direction.

Automatic

Attempts to align the seam points and directions without intervention.

Natural

Moves the seam points to the way they were at the beginning of the command.

Command-line option

Point

Allows picking a location for the start or end of the loft at a point. This tapers the loft to the selected point.

No point object is necessary, but it is a good idea to have some reference geometry in place to aid in picking the point location.

Point steps

  1. At the start or the end of the loft, click the Point option.
  2. Pick a location for the start or end location.

SubCrv

Type subcrv to select part of a curve as input.

Loft Options

Style

Determines the knot and control point structure of the surface.

When some, but not all, endpoints of loft shapes touch, the loft type is restricted to Straight sections to avoid self-intersecting loops in the resulting surfaces.

Loose

The surface control points are created at the same locations as the control points of the original. This is a good option if the control points will be edited later.

Normal

The surface has an average amount of stretching between the curves. This is a good choice when the curves are proceeding in a relatively straight path or there is a lot of space between the curves.

Straight sections

Creates a ruled surface. The sections between the curves are straight.

Tight

The surface closely follows the original. This is a good choice when the input curves are going around a corner.

Uniform

Makes the object knot vectors uniform.

Closed loft

Creates a closed surface, continuing the surface past the last curve and around to the first curve. Available when you have selected three shape curves.

Match start tangent

If the start curve is a surface edge, the lofted surface maintains tangency with the adjacent surface. You must use at least three curves to activate this option.

Match end tangent

If the end curve is a surface edge, maintains tangency with the adjacent surface. You must use at least three curves to activate this option.

SplitAtTangents

If checked, the loft creates a single surface.

If unchecked, the loft creates a polysurface when the input curves are joined tangent curves. Faces in the resulting polysurface correspond to the tangent sub-curves in the input curves.


Original polycurve (left), SplitAtTangents=No (center), SplitAtTangents=Yes (right).

Cross-section curve options

Align Curves

Click the end of a shape curve to reverse the direction.

Do not simplify (A)

Curves will not be rebuilt.

Rebuild with ___ control points (B)

Rebuilds the shape curves before lofting.

Refit within ___ <units> (C)

Refits the shape curves to the specified tolerance value.

DevLoft

Toolbar Menu

New in V6

Surface Creation

Not on menus.

 History enabled

The DevLoft command creates a single developable surface between two curves.

The resulting surface can be flattened by the UnrollSrf command.

Steps

To use the interactive mode

Command-line options

Density

The number of rulings across the surface.

AddRuling

Lines across the surface that define the straight sections on the developable surface. A developable surface can be flattened to a plane by bending along the ruling lines with minimum stretch or compression distortion.

To add rulings

  1. After the initial surface is created, at the prompt, pick a point on one of the curves.
  2. At the prompt, pick a point on the other curve.
    The preview surface updates to reflect the new ruling.

Untwist

Optimizes the rulings.

It may help to run Untwist more than once.

CurvatureDisplay

Visualizes the Gaussian curvature of the surface with false colors.

The analysis mesh density is based on Polygon Mesh Options in the CurvatureAnalysis command.


The Gaussian curvature analysis in the interactive mode. The blue area is where stretch or compression distortion happens when the surface is flattened.

Limitations

See also

UnrollSrf

Flatten (develop) a surface or polysurface with curvature in one direction to a planar surface.

Create surfaces

Wikipedia: Tangent

 

 

 

Rhinoceros 6 © 2010-2019 Robert McNeel & Associates. 16-May-2019