Sweeps generate surfaces and polysurfaces using 2 Primary Curves, rail curves and cross-section curves.

Extrusion vs Sweep

• Extrusions create surfaces be extruding a source curve in 3 ways
  • Parallel extrusion via extrudecrv and extrudesrf
  • Conic extrusion via extrudecrvtopoint and extrudesrftopoint.
  • Curved extrusion via extrudecrvalongcrv and extrudesrfalongcrv.
• Both Parallel and Conic extrusions extrude along linear paths
• Curved extrusions approximate the capabilities of sweep1 and sweep2

Extrusion keeps all isocurves parallel to source curve.

Sweep keeps all isocurves perpendicular to the cross-section curve.

Sweep 1

• All sweep commands are composed of rail curves, and cross-section curves.
• As the name implies, cross-section curves are "swept" and the rail curve.
• Altering which of the two curves is the rail and which is the cross-section produces different results.

Triangle is cross - section

Arc is cross section

• Sweep1 allows only one rail curve, but allows multiple cross section curves.
• Typing sweep1, you are prompted to specify each curve type, followed by a dialogue box, allowing you to specify the type of Sweep.

• Using multiple cross-section curves allows you to transition between curves along a rail.

A sweep1 using a circle as a rail and one arc and one half-circle as cross-section curves.

• Specifying Closed Sweep in the dialogue box will create a surfaces which closes on itself.