When the Automatic Surface Creation option is turned on, a surface is generated from the gradings. Any curves on the gradings are tessellated using the grading group tessellation settings. The grading group is added to the surface as a single operation. It appears in Surface Properties, on the Definition page, in the lower Operation Type box. By default, Automatic Rebuild is turned on for the grading surface. When working on large grading groups in large drawings, you can turn this option off to get better performance. You can add additional surface data, such as points or breaklines, to the grading group surface using the Surface Data commands. You can turn the Automatic Surface creation option on or off, as necessary.
You can also create a detached surface from a grading group by using the Create Detached Surface command, which converts the grading information into breaklines. After it is created, a detached surface is no longer linked to the grading group, so it will not update with changes to the gradings. When surfaces are created from grading groups, boundaries are created around the gradings so that the surface represents the exact definition of the gradings. If the grading closes around on itself, this creates a hole in the surface. To fill in the hole, create grading infill. You can create a grading infill in any region that is entirely enclosed by feature lines. The infill fills up the area that is joined by feature lines.
When refining a particular grading solution, you can improve system performance by temporarily turning off automatic surface rebuilding, and editing the grading style to turn off slope shading and slope patterns. These operations take extra time, and add extra complexity to the grading process. Also, if the base grading does not have a good solution, these operations will not always complete correctly.