Master the cardinal points

The Circle, Polygon and Arc entities have some built-in editing points called cardinal points. The Circle and Polygon has four cardinal points. It might take a little hunting to find all four cardinal points on Circle and Polygon entities, but they are there.

Arc entities have three cardinal points, which are the two endpoints and the arc midpoint.

Note: when duplicating such entities - like when using Push/Pull - the properties also are copied. Position the Move Tool over a Cardinal Point and drag the point to change the radius.

Note²: Circle and Polygon entity cardinal points can be anywhere on an edge, not only on endpoints or midpoints. Where cardinal points are located depends on the orientation of the entity in the modeling space and the number of segments.

If you know the exact profile for a circular vessel-like shape, then draw a profile face and use the Follow Me tool on a circular path. But if you are unsure of the profile – and want to play around with the shape – then moving the cardinal points on Circle entities may be something to try.

A lot can be done starting with just Circle. The Circle has four cardinal points. Three cardinal points are used in the following GIF animation.

• You know an editing point is selected when the selection highlight color disappears.

• Until the entity is disturbed by some non-uniform alteration, the editing points can be grabbed and dragged. When that happens, you can use the Scale tool to make similar adjustments shown in this animation. To symmetrically scale use the modified version of the Scale tool called Scale about Center. That's Scale + Ctrl (PC) or Scale + Option (Mac).

• To rescale to a specific diameter, use the Scale tool to enter the diameter through the active Measurements box. Any number entered during a Move tool rescaling will be the amount of movement for the current procedure.

• Uniformly rescaling a Circle entity with the Scale tool will not break a Circle entity. The Move tool can still grab a control point after a uniform Scale tool operation.

Read more about the Circle tool entity properties in SketchUp Knowledge Center.

If you want to change the end of an existing cylinder, add a circle entity copy to the extrusion with Move + Ctrl (PC) then use the Move tool to adjust the edge and give the shape a little flare.

Additionally, extra circle entities can be created with the Offset tool. Those offset rings retain the circle entity cardinal points too.

Now adding a little flare with an Arc entity....

A Uniform Scale operation will not break the arc entity cardinal point property. There are 2 ways to uniformly scale. The animation shows diagonal scaling about center by using the Ctrl modifier (PC) with the Scale tool. Scale + Shift toggles uniform scaling too from any Scale node (modifying tool tip reminders appear down in the status bar.)

Soften the edge appearance either using the Window > Soften Edges dialog or use Eraser + Ctrl (PC.)

Note³: If the arc has been deformed in such a way that the cardinal point properties stop working, the polyline edges can be selected and the Scale and/or Move tool used instead. Faces and polylines can be Rotated too. And there's always the Smoove (+Shift if needed) tool from the Sandbox extension, though for the Smoove tool to work best, first explode the polyline(s) (select geometry > r-click > Explode.)

Note: Ruby plugin generated bezier curves, like BezierSpline, have their curve properties duplicated when the edge has been copied or a face bounded by such a curve has been Push/Pulled too.

Below is an extruded shape partially formed with a Bezier Curve Tool curve (the first bezier curve plugin developed for SketchUp.) The bezier attributes are retained at each Push/Pull extruded level. To edit, choose the bezier curve with the Select tool, right-click and choose the edit option in the context menu. Move the cardinal points as needed.

Note⁴: The Eraser tool seen in the animation softened the visible geometry when the Eraser tool is used with the Ctrl key (Windows) modifier. Check the status bar for modifying tool tips while the Eraser is chosen.

- catamountain

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