OffsetSrf

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Surface Tools	Solid Offset Surface Offset Surface

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Toolbar: Surface Tools

Solid

Offset

Surface

Offset Surface

The OffsetSrf command copies a surface or polysurface so that locations on the copied surface are the same specified distance from the original surface.

Steps

Select a surface or polysurface.
Type the offset distance, and press Enter.

Command-line options
Distance	Sets the offset distance.
Corner	Specifies how offset corner continuity handled. These options only apply if the offset direction is to the "outside" as shown in the image. Sharp Curves offset to the outside of a corner will be extended to meet at sharp corners with position (G0) continuity. Round Curves offset to the outside of a corner will be filled with arc segments with tangent (G1) continuity.
FlipAll	Flips the offset direction of all selected surfaces. Arrows indicate the positive offset direction.
Solid	Makes a closed solid from the input and offset surfaces by lofting a ruled surface between all of the matching edges.
Loose (Surfaces only)	The resulting surface point structure is identical to the original surface.
Tolerance	Sets the tolerance for the offset surface. Type 0 to use the default tolerance.
BothSides	Draws the offset on both sides of the original.
DeleteInput	Yes Deletes the original geometry. No Retains the original geometry.

Command-line options

Distance

Sets the offset distance.

Corner

Specifies how offset corner continuity handled. These options only apply if the offset direction is to the "outside" as shown in the image.

Sharp

Curves offset to the outside of a corner will be extended to meet at sharp corners with position (G0) continuity.

Round

Curves offset to the outside of a corner will be filled with arc segments with tangent (G1) continuity.

FlipAll

Flips the offset direction of all selected surfaces. Arrows indicate the positive offset direction.

Solid

Makes a closed solid from the input and offset surfaces by lofting a ruled surface between all of the matching edges.

Loose
(Surfaces only)

The resulting surface point structure is identical to the original surface.

Tolerance

Sets the tolerance for the offset surface. Type 0 to use the default tolerance.

BothSides

Draws the offset on both sides of the original.

DeleteInput

Yes

Deletes the original geometry.

No

Retains the original geometry.

Note

Positive values offset in the direction the arrows. Negative values offset the other way.

When a plane, torus, sphere, open cylinder, or open cone surface is offset, the resulting surface is exact. Free-form surfaces are offset to within the value of the Tolerance option.

When offsetting surfaces are joined that are part of a polysurface, there is no guarantee that the offset surfaces will also join into another polysurface. For example, offsetting the six sides of a box will not result in a larger closed box. It will return six separate surfaces with gaps between the edges.

The OffsetSrf command does not maintain the overall structure of the starting polysurface in the offsets. Each surface offsets as an individual object.

Shell

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Solid Tools Solids Sidebar	Not on menus.

Toolbar

Toolbar: Solid Tools

Solid Tools
Solids Sidebar

Not on menus.

The Shell command creates a hollowed out shell from a solid.

Shell only operates on simple, solid, manifold polysurfaces. These surfaces are removed and the remainder is offset inward, using the outer parts of the removed surfaces to join the inner and outer parts.

Steps

Select faces to remove from closed polysurface.
Leave at least one face unselected.
Press Enter when done
This step specifies which surfaces will be removed to make the shelled object.

The top surface of the cylinder was selected for removal.

Command-line options
Thickness	Specifies the thickness for the shell.

Command-line options

Thickness

Specifies the thickness for the shell.

Troubleshoot shelling

Shell and OffsetSrf for polysurfaces are works in progress. There are several known problem areas:

Singular surfaces can cause problems, especially when the offset of the surface must be extended at the singularity. The extensions are done in OffsetSrf (Corner=Sharp) and shelling, which always uses sharp corners. These extensions happen when the offsets of adjacent surfaces come apart. Also, cone-like singularities cause problems in all cases.

Complex vertices (ones with more than three edges) can be problematic, especially in shelling and sharp corner offsets and where some, but not all, of the surfaces at the vertex offset apart.

OffsetSrf on polysurfaces with naked edges, where the naked edges make concave boundaries will not work correctly.

If faces adjacent to the removed faces offset in such a way that the removed face must be extended to fill in the gap, it will fail.

Any surface whose offset self-intersects will cause a problem.

OffsetSrf

Steps

Sharp

Round

Yes

No

Note

Shell

Steps

Troubleshoot shelling

See also