Main Graphics Frame

The main graphics frame is the primary graphics area in the VISRAD main window. It is used to view the target components while setting up the grid, as well as to display results from the VISRAD calculations.

To adjust the view in the main graphics window, use the graphics viewing controls.

Projection Options, Measurement Tools, and Graphics Decorators

The Main Graphics Window can display the view using either Perspective Projection or Orthographic Projection. To change the projection method, select the Show | Orthographic Projection menu item.

When Orthographic Projection is used:

• distance and angle measuring tools are available
• Graphics Decorators can be overlain on the display
• rulers and grid lines can be displayed.

To display rulers, select the Show | Rulers or Show | Rulers and Grid Lines menu items. To adjust the units for the rulers (i.e., the distance between major ticks and grid lines), select the Set | Ruler Units menu item.

Graphics Decorators can also be shown or hidden by selecting the Show | Graphics Decorators menu item.

Perspective Projection

By default, the Main Graphics Window displays the target using "perspective" projection (as opposed to "orthographic" projection). The viewing frustum - i.e., the region that is viewed - depends on the opening angle (q) and by the positions of the front and back clipping planes (see image below). Users can adjust the opening angle (q), as well as the front and back clipping plane positions by the use of multipliers on Z_near and Z_far. To adjust these, select Edit | Preferences, and select the Graphics tab. Adjusting the Z_near and Z_far can often fix"bleedthrough" problems associated with the OpenGL-driven graphics.

Note that a smaller value for the projection opening angle (q) provides a view that is more like orthographic projection (i.e., parallel rays with a view from infinity).

Orthographic Projection

In orthographic projection, the viewing volume is a rectangular parallelepiped (i.e., a box). The cross section of the viewing volume does not change with depth (unlike perspective projection), and therefore projected distances and angles are not affected by their depth in the viewing volume.

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