Tracing

Brief description: Tracing is an interactive (or semi-automatic) vectorization procedure.During the tracing procedure raster objects are specified one by one, these are then recognized by the program and converted to corresponding vector objects. In the process of tracing the original raster objects can be deleted, smoothed or left intact.

Tuning tracing

You should tune the tracing parameters before applying this procedure.
Tracing is tuned in the R2V Conversion Options dialog.
Choose Conversion Options from the Convert menu.

Tuning geometry of traced objects

Open the Options tab of the R2V Conversion Options dialog.

Max.Width - maximum width of traced raster objects. Measure width of the widest traced lines. Set this parameter value slightly greater then the measured width. Max. Break - length of ignored break of raster lines. If you trace dashed lines, set the value of this parameter slightly greater then the maximum gap between dashes.

Accuracy - set the accuracy value for tracing polylines to high (for more precise approximation of raster curves with vector polylines). In other cases increase the accuracy value for images of good quality; and reduce the value for images of poor quality.

Layering resulting vector objects

You can place resulting vector objects on different layers:

• Create the desired layers in Layer Manager.
  See section Layer Manager for detailed information.

Open the Separate tab of the R2V Conversion Options dialog. From the pull-down list of Layer select one to place the traced vector object. Select the Use Table checkbox.

Orthogonalization mode with tracing

When tracing lines and polylines, you can use orthogonalization mode, which allows you to obtain orthogonal vector lines and polylines that consist of orthogonal segments (the base angle can be calculated automatically or specified).

Tracing lines with orthogonalization

IMPORTANT: The operation can only work if the raster line you want to trace deviates from the orthogonal (or specified) direction by no more than 2°.

To turn on line orthogonalization mode:

• Open the Options tab of the R2V Conversion Options dialog.
  Select the Orthogonalization checkbox.
• If necessary enter the base angle value in the Base Angle field, and then clear the Auto Estimate base angle checkbox.       

Tracing with resulting polyline of orthogonal segments

This information is provided in section Tracing polylines with orthogonal segments

Tracing Modes and Commands

Before executing tracing, you should choose a tracing mode.

Tracing modes:

	Original fragment
	Produce vector and keep raster
	Produce vector and erase raster
	Erase raster without producing vector
	Smooth raster without producing vector

Tracing commands

You can trace:

	Lines, arcs, circles with auto recognition		Hatches which consists of lines
	Lines by two points		Raster symbols
	Arcs by three points		Polylines
	Circles by two points		Outlines

How to trace

• Set the tracing parameters
  Information on setting tracing parameters is provided in section Tuning tracing.
• Choose from the Raster to vector toolbar or from the Trace menu:
  • Tracing mode
  • Tracing command
    More detailed information is provided in section Tracing Modes and Commands.
    

Tracing lines, arcs, circles, and outlines

	You can trace raster lines, arcs, circles, and outlines with automatic recognition of their type - click once on the desired object.
	If you work with a complicated image, or an image of poor quality, or you need to vectorize only part of a raster entity, you can apply forced tracing.

Auto extension mode:
When tracing lines or arcs you can use the Auto extension mode - you only need to specify a fragment of the object, but the program recognizes the whole object. To switch to this mode select the Auto extend vectors checkbox in the Trace tab of the R2V Conversion Options dialog.

Tracing Hatches

To trace a hatch, you need to intersect all its lines with a crossing polyline.
TIPS: raster lines that cross the hatch interfere in the recognition operation, so before tracing the hatch, it may be useful to trace these lines and erase the original raster.

Original hatch	Tracing lines that intersect hatch (with erasing the original raster)
Tracing hatch - intersecting hatch lines	Result of hatch tracing (in Produce Vector and Erase Raster mode)

Tracing Polylines

Tracing polylines command produces vector polylines which approximate raster curves. To increase accuracy of approximating vector polyline to the original raster curve increase the Accuracy slider in the Options tab of the R2V Conversion Options dialog. See section Tuning geometry of traced objects for information on tuning tracing.

How to trace polylines:

• Select tracing mode (e.g., Produce Vector and Keep Raster).
  See section Tracing Modes and Commands for more detailed information.
• Run the Linefollowing command.
• Specify a point on the raster curve - the program tracks this curve up to the nearest intersection and waits for you to indicate the direction in which tracing should continue.
  You can also use the Autodetect direction mode:
  Open the Trace tab of the R2VConversion Options dialog.
  Select the Autodetect direction checkbox.
  Set the waiting period (in sec) in the Pause field.
• If you turn on the Autodetect direction mode, and you are satisfied with the autodetected direction, indicated by a cross, press the Space key (alternatively, the program continues tracing after the waiting period expires).
  If you are not satisfied with the direction suggested by the program, specify the right direction on the screen.
  If Autodetect direction mode is off, you must specify the next fragment of the raster curve on screen (fragment between two nodes or between node and end point of the raster curve).
• If you need to change the tracing direction, chose Change direction from the context menu.
• To cancel the last segment of the vector polyline, press Ctrl+Backspace.
• To cancel the last step, press Backspace.
• If needed, you can draw segments in Free Hand Drawing mode. Press Shift and specify the new nodes of the vector polyline on the screen.        
• When you have completed tracing the polyline, press Enter.

TIPS: You can use the Centralize View command from the context menu for convenience.

Tracing polylines with orthogonal segments

When tracing, you can obtain vector polylines with orthogonal segments. For example, this mode can be used to trace buildings on scanned maps.
The direction of the first segment can be estimated automatically or specified.

To obtain polylines with orthogonal segments:

Open the Trace tab of the R2VConversion options dialog. Select the Line Follow Orthogonalization checkbox. Select the Autoestimate Base Angle checkbox or specify the angle for orthogonalization in the Base Angle field or by the measure button.

TIPS: You can reduce the Accuracy value to avoid creating unnecessary segments.
See section Tuning geometry of traced objects for detailed information.

Tracing Outlines

You can trace raster outlines. Tracing results depend on the parameters and mode of tracing. Tracing parameters are set in the Trace tab of the R2V Conversion Options dialog.

Setting parameters of tracing outline
Auto Extend vectors: Off	Creates vector on two colors boundary.
Auto Extend vectors: On	Creates vector at the center of raster line. IMPORTANT: Raster line width is specified with the Options tab of the R2V Conversion Options dialog.
Export single contour: Off	Creates outer and nested outlines.
Export single contour: On	Creates the outer outline only.
Auto Extend vectors: On Export single contour: On Keep raster trace mode	Raster data inside the outline is kept.
Auto Extend vectors: On Export single contour: On Erase raster trace mode	Raster data inside the outline is erased.

How to trace outlines:

• Set the trace outline parameters.
• Specify the tracing mode (for example, Produce Vector and Erase Raster).
  See detailed information in section Tracing Modes and Commands.
• Run the Trace Outline command.
• Specify a point inside the outline.         

Tracing Raster Symbols

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