ACA Structural Member Styles - Part 3A

First Article in the Series (Structural Member Catalog)
Previous Article in the Series (Manually Created Structural Member Shapes)

Manually Created Structural Member Shapes - Fun Facts
Here are a few additional items of interest related to Structural Member Shapes that I have discovered as I was experimenting for the next main article in this series.

1. In order to maintain maximum sanity, set the UCS to World and use the Plan command to orient the screen so that the X-axis is left and right, with positive in the right direction and the Y-axis is up and down, with positive in the up direction. In limited experimentation with a single, 2D polyline as the shape, it appears that the shape will be imported with the World Y axis (or its equivalent, if the plane of the polyline is not parallel to the World X-Y plane) running vertically in the dialog, with positive being up. For example, if you start with the World UCS and rotate the UCS about the Z-axis, that rotation is ignored when bringing the shape into the dialog. When selecting the insertion point, the values of the point selected in the current UCS are used, but are applied relative to the World UCS. In other words, ACA does not translate the insertion point picked from the current UCS to the World UCS, so the insertion point can end up in a very unexpected location, unless it is 0,0 and 0,0 is the same in both the World and current UCS. Someone with a better head for three-dimensional geometry than me may be able to deal with this, but for me, best practice will be to start out with UCS set to World and the screen oriented to the Plan view of the World UCS.
2. 2/10/2012 UPDATE: The following comment only applies to a Structural Member Style that has a single Structural Member Shape assigned to a single component. Insertion points do matter when more complex styles are created.
   2/10/2012 UPDATE 2: Insertion points always matter. The effects I was seeing and which prompted the following comment were due to the fact that all of the Structural Members I had created had their Justify property set to Middle Center, which places the geometric midpoint of the overall assembly at the starting point of the Structural Member. Setting the Justify property of the member to Baseline will place the insertion point of the shape at the starting point of the structural member, provided there are no Y Offsets or Z Offsets. The part of the comment regarding the Low Detail insertion point remains valid, however. Wherever the Medium Detail insertion point of a shape ends up, that is where the Low Detail insertion point for that Shape will also be.
   When assigning a Structural Member Shape to a Structural Member Style, the insertion point selected for the Shape will not necessarily be on the longitudinal axis of the Structural Member. For Medium Detail and High Detail, the shape is intially aligned at the "midpoint", with the midpoint being the point whose X-coordinate is the average of the shape's smallest and largest X-coordinate values and whose Y-coordinate is the average of the shape's smallest and largest Y-coordinate values. Even if you intentionally offset the High Detail insertion point from the Medium Detail insertion point, both will come in with the midpoint of each at the longitudinal axis of the Structural Member. The selected insertion point does matter for the Low Detail geometry, which does not have to be a closed shape and can have lines and arcs. Low Detail geometry will be placed such that its selected insertion point remains aligned with the selected insertion point of the Medium Detail geometry.

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