Positioning Visualizations in a View

Unlike IDL Direct Graphics, the IDL Object Graphics system does not automatically position and size the objects to be rendered. It is up to you, as a programmer, to properly define how your graphic elements will be positioned when rendered.

There are three aspects to this transformation from a generic depiction of your data to a representation that can be rendered to an output device (a graphics destination object, such as a window or printer) with the perspective, size, and location you want.

Viewport

The first aspect is the view of the graphics objects to be rendered: the size of the viewing area (the viewport), the type of projection used, the position of the viewer's eye as it looks at the graphics objects, and the particular view volume in three-dimensional space that will be rendered to the viewing area. These elements of the view of your graphics objects are, appropriately, controlled by properties of the IDLgrView object being rendered. See Viewport.

Location

The second aspect of the transformation is the location and position of your graphics objects with respect to the viewing area. Graphics objects can be translated, rotated, or scaled by setting the appropriate properties of the IDLgrModel object that contains them. See Translating, Rotating and Scaling Objects.

Note
The viewport and location of an object are independent: It is possible, for example, to translate a graphic object so that it is no longer within the viewing area that is rendered in a window or on a printer.

Coordinate Systems and Scaling

The third aspect of the transformation is the conversion between data, device, and normalized coordinates. The IDL Object Graphics system gives you full control over which data values are used, which are displayed, and which coordinate systems are used. This means that you must explicitly ensure that the objects to be rendered and the view object to which they belong use the same coordinate system and are scaled appropriately. This section discusses the properties and methods used to size and position both your viewing area and the graphics objects you wish to render. See Converting Data to Normal Coordinates.