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A setting that applies to both Extruded Shells and Revolved Shells is called Distortion Angle.
In the Extrusion Properties panel of the Shell Settings Dialog we can see a diagram that
shows this angle. The angle called beta in the diagram illustrates how this setting applies.
Its default value is 90 degrees, which means no distortion. Let us set it to 60 degrees.
As you can see the plane of the Profile Polygon has been tilted. As a result the Shell body
is distorted along the vertical direction.
The degree of distortion equals to the sine of the Distortion Angle. This also means that
the distorted vertical dimension cannot be more than the original , since the maximum
value of sine is 1. Let us say that we set the Distortion to 30 degrees. The sine of
30 degrees is 0.5.
If we check this in a Section Viewpoint, the height of the Shell on the right, which we
just modified, has been distorted to half its original size. In all other directions
its dimensions has stayed the same.
With this setting we can distort the half-circle Profile Polygon into a half ellipse. The setting
also applies to Revolved Shells. Again, the diagram in the Settings Dialog
shows how it affects the Shell geometry.
Let us set its value to 60 degrees. The result is that the Revolution Axis, which was vertical,
has been distorted into a slanted line at 60 degrees.
Again, if we check it in Section, we can see that the Revolution Axis is now slanted, but
the vertical distance between its two endpoints stayed the same.
In our examples, the Revolution Axis is vertical. Dimensions in planes that are perpendicular
to the Revolution Axis will stay the same after the distortion.
This also means that the horizontal section of such a Revolved Shell, which is a circle,
stayed a circle after the distortion and was not distorted into an ellipse.