Measuring Objects

You can measure objects directly on screen with a 1:1 scale (that is, real size display) or with a lower/greater scale according to your needs. The Scale Plane mode also lets you select objects.

Before you begin: You cannot use this capability when working with a multiview configuration.

For an optimized accuracy or when using projectors, you need to store your screen dimensions in the following two variables:

  • set CATWidthMMOfScreen=width_in_millimeters (on Windows)

  • set CATHeightMMOfScreen=height_in_millimeters (on Windows)

Do these measurements by yourself using a tape measure. The screen dimensions correspond to the horizontal measurement followed by the vertical measurement. If your computer does not use the full screen for display (for example if there is a strip on the left side and right side of your screen), measure only the part of the screen used for display.

  1. In the power input box, enter c:scale planes, and then press Enter.
  2. In the Scale Plane Properties dialog box, click Apply.
    A plane represented by a transparent grid that lets you visualize the object displayed behind appears:



    The grid is divided into squares. The space between these squares as well as the width and height (in millimeters) correspond to the values displayed in the Scale Plane Properties dialog box.

    In our example, the width is 200 mm and the height is 100 mm. In the picture above, you can see that:

    • The width is divided into 20 squares, each of them being equal to 10 mm (as indicated in the Vertical spacing box).
    • The height is divided into 10 squares of 10 mm each (as indicated in the Horizontal spacing box).

    If you define the space between vertical and horizontal lines to "20 mm", the grid looks like this:



    The width is now divided into 10 squares of 20 mm each and the height into 5 squares of 20 mm each.

  3. In the Scale Plane Properties dialog box, key in a Scale value.

    The default value ("1") provides a real size display whereas "0.5" corresponds to a halfsize display. You can thus measure small objects by entering a scale factor greater than 1 as well as big objects by entering a scale factor lower than 1.

  4. Specify the plane Width and Height in millimeters.
  5. Specify the space between vertical and horizontal by entering a value (in millimeters) in the Vertical spacing and Horizontal spacing boxes, respectively.
    Important:
    • If the value you enter is not a multiple of the value defined for Width or Height, the space between squares is approximated to give a round number (and this may make it more difficult to measure directly on screen).
    • The Show the grid check box lets you display or hide the grid. Display the grid when you are working in a conical projection.
  6. To validate your modifications, click Apply to keep the Scale Plane Properties dialog box open or click OK to validate and close the dialog box.
    Note: Closing the Scale Plane Properties dialog box lets you use the Select command in the Scale Planes mode.
  7. Adjust the viewpoint so that the object is correctly snapped on the grid.

    If you are working in a parallel view (that is, cylindrical projection), running the Scale Planes command moves the user viewpoint so that the object is automatically displayed in the selected scale. Translate the viewpoint horizontally or vertically to align the object on the grid:

    Important: The zoom mode is locked when the Scale Planes command is running ("locked" means that zooming has an impact on the grid position only and not on the display scale to let you translate the grid on the object along its depth and measure the object). Note also that if the grid is far from the object, then the grid disappears because measuring a dimension without the object does not make sense.

    If you are working in a perspective view (that is, conical projection), then zoom progressively until the object is displayed in front of the grid then translate the object as required to align it with the grid and facilitate the measurement:

    Let us view our object that has been correctly positioned. We are now able to measure the hole diameter and we see that the size is comprised between 60 and 100 mm:

    100 mm - 60 mm = 40 mm

    We can also count the number of squares:

    Four squares of 10mm each = 4 x 10 = 40 mm

    according to the values defined in steps 3 to 5.



    Important: Translating or zooming the object does not affect the grid size since its dimensions are defined in the Scale Plane Properties dialog box.