Autodesk 00126-050008-1640A User Guide - Page 130

9 Working with Raster Selection The figure shows that the program has selected the part of the raster line until it meets the intersection with the other raster objects. To select a part of a raster polyline between two nodes 1. At the rSelect command prompt enter j for the obJect option. 2. Click on a point of the raster line that is between these nodes. Selecting Raster Entities Raster entities are raster objects with the same shape as basic vector objects - vector image entities. From here on we shall use the terms raster circle, raster arc, and raster line to imply raster objects that have a shape of a circle, arc, or line. However, you should note that real raster entities might have defects that hamper their identification by the program such as breaks, elliptical arcs and circles, varying width, etc. If the Type Recognition selection type is set, then the Object method can handle both raster lines and arbitrary raster objects with approximately equal width and length. When a raster line is picked, the program identifies the type of raster entity (line, arc or circle) and then tries to select the object of the greatest possible size. It ignores the points of intersection with other objects, and the selection extends until the symbol of the selected object becomes identical to the entity recognized. Since real raster objects may differ from ideal raster entities, the recognition algorithm uses the Approximation Accuracy parameter. This parameter defines the accepted level to which the real raster objects may differ from the ideal ones. For a description of the Approximation Accuracy parameter refer to "Tuning Selection " on page 142. Selecting a raster entity preserves its intersections with other objects. Therefore, transforming and deleting raster data selected when Object Type Recognition is on does not create break in remaining raster objects. This allows you to process raster data in the same manner as you process vector objects. For example, deleting a raster line that crosses the circle leaves the circle intact in the image, exactly as it would when you delete a vector line that lies over a vector circle. In case the raster object selected is not a raster line, the program detects its boundary and selects the object. An arbitrary raster object width should be greater than the maximum allowed width of a raster line. * To distinguish raster lines from other raster objects the program uses the reference value of the maximum accepted raster line width. For 133