This plugin will calculate accurate area properties for planar shapes (centroid, area, perimeter, Moment of Inertia, Radius of Gyration). These shapes must be drawn parallel to the X-Y plane (the ground plane) in SketchUp. Of course these shapes must be closed so that a single face is generated by SketchUp.
To calculate area properties, select one or more faces and choose “Get Face Properties” from the right-click context menu. The plugin will then calculate area properties for each face successively. These will then be displayed in a dialog that allows for copying of values. As final step, a construction point and a set of X-Y axes can be drawn at the area centroid.
To be able to accurately calculate faces that contain internal holes, you must draw lines for each internal hole that connect the hole to the face perimeter (as shown in the image above).
There are other plugins available that use a similar concept and draw a centerpoint. This is usually done for the center of the bounding box, which only in the case of a rectangle coincides with the area centroid. Please note also that the accuracy of the calculations is dependent on the accuracy of the polygonal shape. While SketchUp draws lines accurately, curves are always approximated by a polyline.
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