Autodesk 00126-050008-1640A User Guide - Page 165

WiseImage - User's Guide Selecting an Image for Tracing Selecting an image for tracing is performed using the following rules. If there is only one available (visible, placed on an unlocked layer) image in the drawing, then the operation will be performed on it. Otherwise you should select an image. You can select an image (as an AutoCAD object) before starting the command, or later using the selection dialog box. * For more detailed information on selection procedure see "Selecting a Single Image" on page 19. Tracing Methods Various methods are used to trace raster objects. The tracing method sets a user's sequence of operations and defines the type of vector object used for approximating a raster line. * The operation to be applied to the results of raster object tracing (vectorization, converting, erasing, smoothing) is set by the current tracing mode. For detailed information see "Tracing modes", page 181. Tracing involves local recognition of vector objects on the raster image. For correct identification of objects the program always uses two numerical parameters defining the maximum width and the ignored break value of a raster line, and also a parameter that specifies the level of accepted deviations of the raster objects from their vector prototypes. You can set these parameters in the Options tab of the Conversion Options dialog. To trace raster symbols you should create recognition templates or use the existing samples and specify additional parameters for symbol recognition. During tracing you can apply the Line Follow Orthogonalization mode, and the program will align obtained vector objects in parallel and perpendicularly to the Base Angle. The base angle can be defined automatically or set in the Options tab. This mode can be used, for example, to trace urban maps with buildings. * Detailed information on the parameters defining tracing operation is provided in the section "To setup tracing parameters" on page 183. Tracing with Automatic Object Type Determination (Trace Auto) This method is used for tracing raster entities of the following existing types: line, arc, outline and circle. When tracing in the automatic mode you specify a point on a raster line, and the program automatically selects the type of vector object (line, arc or circle) that is most suitable for the specified raster line and vectorize the specified raster object. If the indicated object cannot be approximated with one of the above objects, and its width exceeds the value specified in Max Width, then the program creates a vector outline of this object. 170