3D Solids with Z Tools
Using 3D tools with other standard 'engine' tools you may digitize 3D shapefiles. If you can imagine it, you can do it! And best of all, its easy.
This all starts with 9 'Z' points!
This is a 3D view in theEngine of a polygonZ shapefile. The polygons in this case are triangle features with differing elevations at each node. No, you do not create a TIN from random points nor do you draw each and every triangle.
This looks complicated, but in fact it is quite easy to do. It all starts with only a few 'Z' points plotted in outline, just as you would on graph paper.
This next drawing is an amalgamation of some of the steps along the way. If you look at the points in plan view what you see is a set of pointZ features plotted into a shapefile using the 'eyeglasses' and the 'Set Z Value' tool.
A single row of points are plotted in a straight line, much like a graph in plan view. You can't see the graph but it is there.
You can flip left/right to look at them. The 3D view of the points and triangles shows this. Only the first row of points are plotted and they represent the outline of a solid, in this case the building.
The hard part is over, the rest is just copy and rotate.
Next, the other row of points are added by copying the first set back to the file (but not the apex). At first you see nothing (because they are on top of the originals), but if you open the table you see the added records. These new records are to be rotated around the apex, by an amount equal to your circular divisions, in this case, 11.25 degrees. Capture the apex point into the clipboard, (features-to-graphics, Ctrl C), this is preserved for the whole exercise. Open the table, make sure the 'id' field is 'on', and select the added points. Rotate them -11.25 degrees, and save. You should see the points in a pie shaped pattern shown above.
Make a polygonZ file, with no attributes just as you would any shapefile with theEngine.
The next task is to make the core 3D polygons and send them to this polygonZ file. You make them from the pointZ features in the point file. Using the features-to-graphics tool select 3 points that form the corners of one triangle, make them active. Make the polygonZ file active, go to the 'assemble graphics' function and convert them into polygons, they will automatically become polygonZ graphics if the originating points are Z types. Make active and sent them to the file (press F8 then F9). Repeat until you have all the triangles made.
Make the vertical slab by plotting the corners or taking the points from the table. You may flip down to put the hole into the slab as shown here, then flip back up.
At this point you should have a file that looks like the 3D polygons above.
Obviously, these are the components that you replicate, and rotate into position, until it starts to look like the plan view of the first 180 degrees as shown, and the final file shown below.
This is like any CAD replicate function, except that you do it manually. But the trick is to perform it in summation sequence.
In this example, copy everything in the file, back to the file (a duplication), select the newly copied features, and rotate just these. The first time you rotate -11.25, the next time -22.5, next -45, next 90, then 180, and you are finished.
The trick is this, you copy everything on to itself, and keep track of the last id number before you do, then you select all from the last id onward, in the table, rotate, and repeat.
Remember the point graphic you stored in the clipboard? Yes, that is the point of rotation you choose in the rotation dialog box, and must be called back.
You are not restricted to a rotation replication, remember that there is a translation function available, which you would use to replicate in a linear fashion. With a little bit of practice you should be able to create any reasonable 'solid' shape.
You end up with a 'solid' polygonZ shapefile.
With theEngine's 3D Extrude function you can look at your design in a variety of ways. The function rotates
into 3D view only selected features (or all if nothing is selected), all active themes at once, and of course
they can be moved about the screen at will.
The 3D rotated features are save into a shapefile if committed. Using this knowledge, some interesting views you might try are as follows.
Since your features are stored in a shapefile, you may view a solid at any angle...
including 90 degrees for an elevation view...
and 'legend' to any colour scheme....
or view just selected parts of the file.