(By Pierfrancesco Parente and Robert Byrne)
Spin uses the Z axis of the object as the pivot point and the
first and last points should be at the same X coordinates otherwise the
object will be lop-sided. Sweep, on the other hand uses the first and
last points of the outline as the pivot.
Z
. -------
FRONT VIEW . /
. /
. /
. /
. /
X................./...
. /
. /
. /
. |
. |
. |_____
. |
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.
If You Spin this object the top will be closed with its centre
offset. If You Sweep it the top will be open and symmetrical.
You have to remember:
- BOTH Spin & Sweep use the Z axis as the pivot;
- Sweep rotates ALL the points of the outline around the pivot;
- Spin rotates all the points of the outline BUT the first and the
last ones, which just remain in place.
Spin is useful when trying to build a closed top/bottom lathe
object (paying care that the first and the last points of the outline
fall right on the Z axis), since Sweep fails in this. Also Sweep is to
be used when the outline to be spun is a closed one (e.g. when making a
torus of a circular outline) since Spin is definitively not recommended
for this.
SP & SW always rotate the object along the local Z axis of the
object, so You can obtain different kind of rotations by moving or
rotating the object's axes only (select "Transform Axes Only" in the
Transformation Requester or press the Shift button in interactive mode).
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