The VIEWOPT command lets you access the screen drawing view related options via a GUI dialogue window operation. These options, such as the fast linetype generation, smooth ellipse representation, quick text mode control and fast text curve stroking, are controlled by specific system variables. With VIEWOPT, you can easily access these options without knowing how to setup these related system variables.

VIEWOPT will pop up the dialogue window as shown below:
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The following describes these screen items in details.

Linetype Generation Group

There are two ways to generate a screen linetype.

  • Rough but fast     The pattern linetype will be generated in graphic driver level, which is fast but not very precise to the definition of the pattern linetype. The pattern linetype will not be adjusted for both end points of a line.
  • Precise calculation     The pattern linetype will be generated with precise calculation such that the screen view will be exactly as what is expected from the printer/plotter output.

Note that this option is effective to screen linetype only. It will not affect the printer/plotter output.

Ellipse Generation Group

There are two ways to generate an ellipse on the screen.

  • Smooth Arcs     The ellipse will be drawn with successive smooth arc segments that approximate the ellipse to a very high precision. For a whole ellipse, this approximation will take up 32 arcs.
  • Chord Lines     The ellipse will be drawn with successive chord line segments. It is faster but may have undesired polygon effect if the stepping chord angle is too large. You may control the fineness of the ellipse by specifying a proper chord angle.

Note that this option is effective to the ellipse drawn in the screen. It will not affect the printer/plotter output.

Text Font Generation Group

You may choose to display only the bounding boxes of texts in the screen without actually drawing the text stroke details, to faster up the drawing regeneration during your drawing editing session. Or, if you prefer, you may specify a threshold control value for TwinCAD to decide which texts will be drawn with stroke details and which will not. This threshold control value is defined as the ratio of the text size in height to the height of the drawing window, given in percentage. All texts that are smaller than this threshold value, will be drawn with bounding boxes only.

Text fonts from TrueType or PFB files may contain Bezier curve elements. TwinCAD will realize these elements with smooth arc segments when the text fonts are drawn, plotted or exploded. However, if you are using a lot of TrueType fonts or Adobe's PFB fonts in the drawing, you may like to speed up the drawing view regeneration by specifying to draw the Bezier curve elements using fixed line segments. Note that this option will not affect printer/plotter output, nor the result of text in explosion.

Miscellaneous Options Group

There are other interested options in this group.

Enable Solid Area Color Filling

If this option is enabled, all entities with solid color fill attribute (such as Circle, close Polyline, Region, Text) or with wide line property will be actually filled with specified solid color in the screen. Otherwise, only profiles of these solid areas are drawn. You may turn off this option to speed up the drawing regeneration.

Enable Solid Area Polygon clipping

If this option is enabled, a solid area of color fill will be clipped with the virtual drawing window before it is passed to the graphic driver for color rendering. If you turn off this option, TwinCAD will temporarily turn off the solid color filling if one should be not totally within the virtual drawing window, which will speed up drawing regeneration.

Background Drawing Regeneration

If this option is enabled, TwinCAD will regenerate the drawing in the background bitmap first and then show the bitmap to the foreground window at once. Doing so would be faster in drawing regeneration, yet without the real time feeling.

Automatic screen refresh

If this option is enabled, certain prime commands will issue screen refresh request to redraw the screen, so that these highlighted objects (on temporary basis) or pointer markers (blip mark) will be removed immediately from the display. This refreshing will cause TwinCAD to clear the graphic window and redraw the display list again. Usually, this is fast and latent to the operator.

However, if you turn this option off, these highlighted objects will be removed in another way, which may be faster but the blip marks will not be cleared.

This option is controlled by AUTOREDRAW variable.

Generate blip mark upon pick point

If this option is enabled, TwinCAD will generate a point marker (in small crossline) right at the snapped position when you pick up an object or designate a point. The marker thus generated is not part of the drawing, yet helps you to identify the pickup operation. It will be removed when the screen is refresh by the REDRAW command.

This option is controlled by BLIPMODE variable.

Enable object highlight in selection

If this option is enabled, all objects in selected state will be highlighted in the screen, so that they can be clearly identified by the operator. If this option is off, selected objects will not be highlighted.

This option is controlled by HIGHLIGHT variable and is intended for TCL application to fast up the command processing.

Show hidden boundaries/edges

If this option is enabled, the drawing regeneration will also draw out hidden boundaries (associated hatch regions) and edges (3DFACE).

Coordinate decimal position

This is a value entry, specifying the number of decimal position for the screen coordinate display. If it is zero, 3 decimal position will be used but the trailing zero will be removed.

Other Buttons

After completing your option setup, you have to press the [OK] button to confirm the change and terminate VIEWOPT. Or, you may press the [Cancel] to quit VIEWOPT operation. You may also press <ESC> key or the right mouse button to quit the operation.

Special Notes:

The VIEWOPT command is an external command provided by the TCL program file "VIEWOPT.TCL" or "VIEWOPT.TCA". Either file must be present in the COMMANDS sub-directory where the TwinCAD resides. If you can not issue VIEWOPT command, you may solve the problem by copying the "VIEWOPT.TCL" or "VIEWOPT.TCA" to the COMMANDS sub-directory.

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