Vulcan - Lines and Polygons | Mining University

Vulcan - Lines and Polygons

Many of the CAD functions in Vulcan are created in the same manner and share common properties.  Lines and polygons are two objects that differ in fundamental ways.  These differences are not detrimental to the user in either case but you should know what the differences are so that you are not surprised when they show up in the normal course of work.
In some other drafting programs (AutoCAD) the difference between a line and a polygon is simply the fact that the first and last points share the same coordinates.  This seems intuitive enough as you are digitizing data but when you stop to think about it, there are really more points on the line than are needed.  A square with four corners would, in this method, need five points (the first and last being the same). 
There is also the problem of the point snap.  I’m sure that all of you are conscientious digitizers and always use the snap to points mode when creating a closed polygon, but what about your co-workers?  When working with a polygon digitized by someone else, how do you know that it is actually closed?
 
In Vulcan the difference between lines and polygons is that the polygon has a flag that says the first point and the last point should be connected.  This removes the ambiguity of having to snap to the first point (or not) and gives the user an attribute that can be queried to find out if the object is closed.
For two objects that are so similar, the dissimilarity of what is created is really surprising.  To illustrate, this let’s create some lines and polygons.
Lines:
1)      Design > Create > Line
2)      If no layer is current you will be prompted to create a layer
a.      Enter a name in the ‘Layer’ field
b.      Enter a description in the ‘Description’ field
c.      Click ‘OK’
3)      The Vulcan prompt (top middle and bottom left of the screen) instructs you to ‘Indicate first point.’  Click a point on the screen.
4)      After the first point has been indicated the prompt will change to ‘Indicate next point.’ 
5)      Notice the rubber band line between the cursor and the first point.  When you indicate the next point this line will become the new segment of your line.
6)      Click two more points.
7)      Right click to cancel out of indicating points on this line.
8)      Notice that you have not canceled out of the option completely and that the prompt has changed to ‘Indicate continuing point’
9)      Indicate a point in the primary window.
10)   The prompt has changed back to ‘Indicate next point.’ 
11)   Click two more points.
12)   Right click twice to completely cancel out of the create line option.
Before we look too closely at the lines that we have created, let’s create some polygons.
Polygons:
1)      Design > Create > Polygon
2)      The Vulcan prompt (top middle and bottom left of the screen) instructs you to ‘Indicate first point.’  Click a point on the screen.
3)      After the first point has been indicated the prompt will change to ‘Indicate next point.’ 
4)      Notice the rubber band line between the cursor and the first point.  When you indicate the next point this line will become the new segment of your line.
5)      Click two more points.
6)      Right click to cancel out of indicating points on this line.
7)      At this point you will see that a segment has been added between the first and last points of the polygon.   It is now closed.
8)      Notice that you have not canceled out of the option completely and that the prompt has changed to ‘Indicate first point’
9)      Indicate a point in the primary window.
10)   The prompt has changed back to ‘Indicate next point.’ 
11)   Click two more points.
12)   Right click twice to completely cancel out of the create polygon option.
The creation method for lines and polygons is almost exactly the same.  If you play around with these options for a while you will notice that the create polygon option requires you to digitize at least three points for each polygon while the create line option will allow for a single point per line.  The big difference between the two objects becomes apparent when we select them. 
Click on one of the lines we digitized.  What happens?  Both of the lines highlight in Vulcan.  The two lines are the same object. 
Now, click on one of the polygons.  What happens?  Only one object is highlighted.  The polygons are two separate objects. 
I don’t know why these seemingly similar objects behave so differently in Vulcan.  I do know that it can be frustrating, later on, to have objects that you thought were separate turn out to really be the same.  Just remember that if you want to digitize lines that are separate objects you mush right click twice and re-select the create line option between each line. 
Now that the objects have been created it is tempting to use the Design > Object Edit > Explode option to break the lines into separate objects.  DO NOT DO THIS!  The explode option goes way beyond breaking the lines into different objects and makes each segment a new object.  Instead, use the Design > Object Edit > Split option.  This option has a nice little sub-function called ‘Split where disconnection exists’ that will do what you are thinking of.  I will explain both the explode and split options in a later post.
Creating lines and polygons is a powerful tool in creating a mine design, just don’t be fooled into believing that the ‘objects’ created are equal.

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