At times, you will want Civil 3D to calculate the location, shape, and elevations of feature lines rather than designing them yourself. Examples of this situation would be projecting a slope through a certain distance or elevation or finding the intersection of a slope with a surface. For these cases, Civil 3D provides the grading object.
Figure 17.8 shows a pond design composed of several grading objects, each one using a different set of parameters to calculate an edge that defines the shape of the pond.
 |
| Figure 17.8 A pond design composed of grading objects |
A
grading object is a collection of feature lines whose geometry, location, and elevation are calculated by Civil 3D based on design parameters that you have applied to a feature line. That’s quite a daunting definition, so here’s a look at it broken down into several parts:
- A grading object is a collection of feature lines (and other things not important to name at this time), so it behaves as one object. The feature lines in this collection have many of the same characteristics as individual feature lines as well as some unique characteristics that relate to being part of a grading object.
- Everything about a grading object is calculated by Civil 3D. Very similar to the way that Civil 3D calculates a corridor, grading objects cannot be edited directly, but they respond automatically when their design parameters are edited. This is a little different from an individual feature line, which you can grip edit at will.
- You assign the design parameters to a feature line. To create a grading object, you start by picking a feature line in the drawing. The design parameters you provide, such as slope, distance, elevation, and so on, are projected from this feature line to create the resulting grading object. A feature line that serves as the basis for a grading object is called a baseline.
