Guided loft: Create a surface using Variation options
Description: 5 minutes; Lab exercise: 20 minutes
Choose from three variation options to modify your
guided loft surface.
- Scalar - Scaling
is applied to the profiles with respect to the spine.
When a profile is
calculated for a certain position of the spine, this position is the center
for the scaling.
The correlation of
this position and the calculated profile depends on the original attachment
points.
(An attachment point
is the intersection of the profile's plane and the spine.)
For non-planar or non-orthogonal profiles where
the attachment point position is not clearly defined, the result may be
unexpected.
- Angular - Specify
an angular variation along the spine. The profile is rotated or turned with
respect to the spine. The attachment point is the center for rotating. The
tangent of the spine is the rotation axis.
Use the
Orientation Options to
influence the twisting of the surface around the spine.
- Offset - Specify
an offset value to be modified along the spine.
Lab exercises
Create a surface with scalar variation
- Save the file
variationOptionsScaling.pkg on your system.
- Load the variationOptionsScaling.pkg file.
- Click Surfacing
.
- Click Guided Loft
in the Create Face section.
- Select the line as the
Spine.
- Select the box as the
Profile Edges.
- Click Preview.
- Expand Variation Options
and choose an option from the Scalar
drop-down menu.
- As you change options in the
Scalar menu, type values and weights
into the dialog to see what happens to the surface with each situation. The
larger the weight, the longer the scale value is kept before the other value
is used for sweeping the profile along the spine.
- For the Three Values
option, a Mid Par option is
available.
The midpoint can
be shifted forward or backward on the spine in order to change the shape of
the surface. Typing a value between 0.1 to 0.9 will move the mid point
closer to either the start or end point.
- For the 2D Curve
option, you must have a spline curve created on a workplane. The U axis of
the workplane is mapped to the spline curve. The values of the spline along
the V axis are used as the scaling function's values. (For more information
on the 2D Curve and Origin, see 2D Curve.)
- Select the 2D curve
on the workplane.
This curve is
used to scale the profile.
- Select the Origin
by clicking a 2D point on the workplane.
The origin has
an influence on the V value of the 2D curve.
If the distance
between the start point of the 2D curve and the origin is 1 (the origin
can be anywhere along the U axis), the scaling value at the start of the
spine is 1. The distance between the 2D curve and the origin is measured
in mm.
1mm = factor of
1.
- Click
to
complete the operation.

Scalar:
Three Values with Start and Mid at 1,
End at 2, Start Weight and End Weight at 1, Mid Par at 0.7.
Create a surface with angular variation
- Save the file
variationOptionsTurning.pkg on your system.
- Load the variationOptionsTurning.pkg file.
- Click Surfacing
.
- Click Guided Loft
in the Create Face section.
- Select the line as the
Spine.
- Select the box as the
Profile Edges.
- Click Preview.
- Expand Variation Options
and choose an option from the Angular
drop-down menu.
- As you change options in the
Angular menu, type angle values and
weights into the dialog to see what happens to the surface with each
situation. The larger the weight, the longer the scale value is kept before
the other value is used for sweeping the profile along the spine.
- For the Three Values
option, a Mid Par option is
available.
The midpoint can
be shifted forward or backward on the spine in order to change the shape of
the surface. Typing a value between 0.1 to 0.9 will move the mid point
closer to either the start or end point.
- Click
to
complete the operation.

Angular:
Three Values with Start and End at
0, Mid at 90.
Create a surface with offset scaling
- Load the
reduced.pkg file.
- Click Surfacing
.
- Click Guided Loft
in the Create Face section.
- Select the long curve as the
Spine.
- Select the smaller curves on either side of the spine as
the Profile Edges.
- Click Preview.
- Expand Variation Options
and choose an option from the Offset
drop-down menu.
- Type a value in Offset.
The offset is a length value applied to the profile. The value can be
positive, negative, or zero.
For a specific point on the profile,
the offset direction lies in the profile plane and is measured from the point
toward the face normal (shiny side) of the surface. A negative offset or a
negative scaling leads to an offset to the -face normal (dull side).
- Modify the offset value with a scaling function that will
modulate the offset value along the spine. Select an option from
Scale along Spine.
These options
are the same as those in scalar variation.
As you change
options in Scale along Spine, type
values and weights into the dialog to see what happens to the surface with
each situation. The larger the weight, the longer the scale value is kept
before the other value is used for sweeping the profile along the spine.
- For the None
option, the offset value is applied to the entire surface.
- For the 2D Curve
option, you must specify a 2D Curve and Origin. (For information about the
2D Curve and Origin, see 2D Curve.)
- For the Three Values
option, a Mid Par option is
available.
The midpoint can
be shifted forward or backward on the spine in order to change the shape of
the surface. Typing a value between 0.1 to 0.9 will move the mid point
closer to either the start or end point.
Use Reverse
to switch the start and end points of the 2D curve.
- Click
to
complete the operation.

Offset: Offset: 0.2 inches;
Scale Along Spine: 2D Curve
2D Curve
The distance in the direction of the V axis is interpreted as the "value" of
the function at the U position (a relative position on the spine between the
start and end of the spine).

The Origin is shown by the construction point. The 2D curve has a start
position at the first construction line and an end position at the second
construction line. The vertical line shows the distance - in the V direction -
between the U position of the spine and the origin.
A 2D curve that contains two V values (on the vertical line) for one U value
(relative position on the spine) cannot be used as a function. If a vertical
line (parallel to the V axis) intersects the curve more than once, the curve
cannot be used for scaling.

The Origin is shown by the construction point.
The V direction
intersects the 2D curve twice.
The 2D curve cannot be negative, or smaller than the V value of the origin
because the distance would be negative and the surface would be
self-intersecting.

The Origin is shown by the construction point.
The 2D curve and the
function become negative with respect to the V value of the Origin.