Visio 2003 Developer's Survival Pack Tools and Samples
GeoHelper browser
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Overview

GeoHelper provides a way to view and understand Polyline and NURBS geometry types, and also provides some NURBS editing features.

ScreenShot

Operation

Special NURBS-Related Features

Control Point Impact Range

Selecting a grid cell in a Ctl column moves the graphic that indicates the span of T over which this control has influence.

Control Polygon

You can use the Ctl Shape checkboxes to show the NURBS's control polygon, which looks something like this:

The black line is the NURBS shape, and the red line is the NURBS control polygon. The red square shows the currently selected control point in GeoHelper. (Unfortunately, it's not possible for a tool such as GeoHelper to read or set the currently selected handle on the drawing page.)

(There are two checkboxes: One enables the control polygon shape, a relatively slow operation, and the other allows quickly showing/hiding the control polygon shape.)

Insert Control Point

Visio itself does not have a way to insert a single control point into an existing NURBS curve (see book for details). GeoHelper provides this function.

First, with the control polygon enabled and visible, select a cell in one of the Ctl columns and note that the red square moves to indicate the control point selected. Now if you hit the Insert Control After button, GeoHelper wil; insert a control point right after the selected control point.

Issues

GeoHelper attempts to be a fairly "live" tool -- edits you make in GeoHelper automatically feed to the drawing, and vice versa. Edits to either place are automatically reflected in the control polygon, if visible. But this also means that GeoHelper generates a lot of cell-writing activity. This sends a lot of data to the Undo queue, which makes the Undo function not very useful. It's probable that bursts of GeoHelper actions could be sensibly wrapped in Begin/EndUndoScope, but I have not invested the time to do that properly, as this is intended to be primarily an exploratory tool, not an end-user production tool! 

Release History

Date Version Number Description/Issues
2003-10-21 0.3.0.0  
     
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Article Created: 2001-06-01  Last edit: Last edit: 03-10-29 Graham Wideman
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