Tablet: TABLET

Menu: Tools > Tablet

Keyboard: _TABLET

Alias: TA

Shortcut: F4

Controls tablet configuration for tool selection and calibration for digitizer input.

CADdirect supports digitizer tablets compatible with the Wintab driver and comes with its own tablet overlay. For instructions on installing the tablet driver and using the buttons on your pointing device, refer to your hardware documentation. For instructions on customizing the overlay menu choices and tablet buttons, see Customizing the tablet interface.

Three options are available with the Tablet command:

• Configure - Maps the tablet overlay to the tablet itself. Configure the tablet if you plan to select CADdirect tools from the tablet overlay.
• Calibrate - Maps points on the tablet, in absolute coordinates, to points on a drawing. Calibrate the tablet if you intend to digitize points. This is convenient for tracing paper drawings.
• Tablet ON/OFF - Turns tablet mode (digitizer mode) on and off. Use this to switch between tool selection and digitizer input.

Before you begin

Slip the tablet overlay underneath the tablet's plastic cover and align in accordance with the directions for your tablet.

Tablet: ON/OFF/CALibrate/ConFiGure/<On>:

To configure the tablet for menu input

Type CFG or choose Configure.

Do you want to align the tablet overlay? Yes/No/<No>:

If your tablet is 12" x 12", CADdirect provides a default configuration. To accept the default, choose No.

NOTE  If you choose the default configuration, make sure the commands in the grid are being correctly activated. If the default alignment does not work for your tablet, reconfigure the tablet and answer Yes to align the tablet overlay yourself.

Digitize upper left corner of the overlay: Click the tablet pointer on the upper left alignment point of the overlay ().

Digitize lower left corner of the overlay: Click the tablet pointer on the lower left alignment point of the overlay ().

Digitize lower right corner of the overlay: Click the tablet pointer on the lower right alignment point of the overlay ().

Digitize lower left corner of the Screen Pointing Area: Click the tablet pointer on the lower left alignment point of the WORKSPACE area of the overlay ().

Digitize upper right corner of the Screen Pointing Area: Click the tablet pointer on the upper right alignment of the WORKSPACE area of the overlay ().

Click points in the order shown to configure your tablet for menu input.

NOTE To use the tablet for tool selection, tablet mode must be turned off.

To turn tablet mode on or off

Type ON or OFF or choose On or Off. You can also press the F4 key to toggle tablet mode on or off or double-click TABLET on the status bar.

To calibrate your tablet for digitizing points

You must specify at least two points for tablet calibration. However, the more points you specify, the more accurate the transformation between the tablet and the screen points. Specifying additional points is particularly useful if you plan to trace a paper drawing that is not orthogonal, such as an aerial photograph.

You can specify a maximum of 10 points.

Type CAL or choose Calibrate.

Digitize point # 1: Click a point on the tablet to define as the first calibration point.

Enter coordinates for point # 1: Specify a point within the CADdirect drawing window to correspond to the point you digitized on the tablet, or enter coordinate values in the command bar.

Digitize point # 2: Click a point on the tablet to define as the second calibration point.

Enter coordinates for point # 2: Specify a point within the CADdirect drawing window to correspond to the point you digitized on the tablet, or enter coordinate values in the command bar.

Digitize point # [3-10] (or ENTER to end>: To specify more than the two points required, click a point on the tablet to define as the third calibration point. You can enter up to 10 points.

Enter coordinates for point # [3-10]: Specify a point within the CADdirect drawing window to correspond to the point you placed on the tablet, or enter coordinate values in the command bar.

Select Transformation type: Orthogonal/Affine/Projective:

Type O, A, or P, as appropriate.

Depending on the number of points specified, you have a choice of transformation types to use, along with the type recommended by CADdirect.

Transformation refers to the calculation of the points on the screen that correspond to points you digitize on the tablet.

• Orthogonal: Preserves all angles between lines, preserves all relative distances, and, in general, preserves shapes. If you specify only two points, an orthogonal transformation is automatically generated. The orthogonal transformation type yields the most precise mapping between the digitized points on the tablet and the corresponding points on the screen.
• Affine: Preserves parallel lines, but not necessarily the angles between intersecting lines. If you specified three points, CADdirect can no longer represent this mapping as an exact orthogonal transformation. Therefore, you have a choice of an exact affine transformation or a "best fit" orthogonal transformation.
• Projective: Does not preserve parallel lines or angles. If you specify exactly four points, you have a choice of an exact projective transformation or a "best fit" orthogonal or affine transformation.

Choose the recommended type unless you know it will not be appropriate for what you are digitizing. The most appropriate type is not always the one with the least error; for example, you might digitize three points and select the orthogonal transformation, even though the affine transformation would yield a closer representation of your calibration entries.

Example

Digitizing on tablet.

Corresponding coordinates:

1. Coordinate specification X0, Y0, Z0
2. Coordinate specification X0, Y5, Z0
3. Coordinate specification X5, Y5, Z0
4. Coordinate specification X5, Y0, Z0

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Customizing the tablet interface