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Chapter 1 Using the Grading Commands
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Grading Objects and TIN Surfaces
TIN Results from a Grading Object
Verify TIN results when creating a surface from the grading object: For most
grading objects, the Create Surface command in the Slope Grading menu will
create surface TINs that do not require any modifications. However, there may
be situations where you may need to clean up the TIN prior to using it for
analysis or design. In most cases where there are problems, it is due to crossing
daylight lines or TIN lines outside of the daylight line which were not detected
for cleanup during the TIN creation process.
It is important to understand that the daylight line is always treated as a
boundary, and the footprint is not. In cases where TIN lines need to be edited or
deleted (whether within the object or potentially outside of the daylight line),
you should edit the TIN using the standard editing commands in the Terrain
menu. An alternative solution is to explode the grading object before creating a
surface, and then make edits to the resulting entities so that they will create a
valid surface.
Grading Objects and Terrain Model Explorer
Grading objects cannot be directly selected as valid Terrain Model data: You
can create a terrain model from a grading object, but you cannot directly use a
grading object as surface data in the Terrain Model Explorer. However, you can
create breakline data from the grading object for any surface by using the Create
Breaklines command, or you can explode the grading object into 3D entities
and use these entities (in conjunction with other point, contour, and 3D CAD
data) to create a surface in the Terrain Model Explorer.
Footprints
Keep the Grading Footprint Simple
Keep your grading footprint as simple as possible: Complex 3D polylines
created using the commands in the Daylighting menu typically have far more
vertices than are needed to define a grading object. A corner cleanup method is
applied to each vertex on a grading object, which requires calculation time. The
intent of the projection spacing (accuracy) is to eliminate the need for
additional vertices. Also, applying elevation changes to the footprint is easier
and more manageable if the footprint has fewer vertices.
Raising and Lowering a Footprint
When using the Ctrl + and Ctrl - keys to raise or lower a footprint, give the
program a chance to finish calculating: If you press the keys repeatedly before
allowing the program to finish calculating, the keyboard memory buffer may fill
up and cause these keypad commands to stop functioning. This may also affect
the display of the shortcut menu when you click the right mouse button.
If this happens, it is usually necessary to exit AutoCAD to restore these
functions. This will not cause loss of data or inability to save the drawing. Note
that all other commands will still be available, and all commands in the
shortcut menu can still be accessed through the Grading pull-down menu.