Understanding Segments of Visio Geometry

I recently had to revise my understanding of the POINTALONGPATH(…) function in Visio because I was getting a #REF! error in some cases. My particular scenario requires a line with a number of vertices that are initially all in a straight line but can be moved by dragging controls around that each vertex is bound to. My assumption had been that a segment of a path is always between vertices in a geometry section, but this is not the case. So, I thought I would look deeper into the ShapeSheet functions of paths and segments. The following screenshots show a series of ShapeSheet formulas and the result of them on a single line that has 4 vertices that can be moved using a yellow control that they are bound to. Notice how the PATHLENGTH(…) formula fails to understand the segment parameter until the vertices are moved.

In case the screenshots are a little dry, I have recorded a short video to explain further.

My own need was for a boundary shape around some other shapes where I wanted to make the segments disappear if they were outside of the Visio page. The unexpected #REF! values were causing distortions because the co-ordinates were failing to update.

However, I can see that this understanding of line segments and points will be useful in many types of diagrams.

For completeness, I thought I would try the same exercise with a PolyLineTo row rather than multiple LineTo rows.

The PolyLineTo formula does have the advantage of being a single row, but this means that the PATHLENGTH(…) function does not have a segment index to that can be used to calculate with. In fact a PolyLineTo row does have two segments, but the last one is always 0 length!

However, I was able to calculate the lengths of each segment in both cases, by using the co-ordinates of the Controls in the Tip cell for each Controls row with the SQRT(…) and POW(…) functions..

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