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# View Manipulation and Behaviour

There are several different ways to manipulate the view of you data in ParaView. In the upper left corner of the application is the view toolbar. The first button on this toolbar resets the view to all the visible data sets.
If you would like to reset the view to show a single data set, you should press the "Set View To Data" button on the data's display page.

The remaining buttons activate different interactors states. The current interactor state is indicated by the highlighted button, and special cursors when the mouse is over the render window.

The "Fly" interactor causes the view to move toward where the cursor is pointing. When the cursor is in the middle of the view, the interactor zooms. When the cursor is near the edge of the view, the fly interactor pans the view. This interactor is most useful when trying to position the view internal to several elements. The left mouse button flys forward, and the right mouse button flys backward. None of the interactors use the middle mouse button.

The "Rotate" interactor is the default interactor. Its behavior also depends on where the cursor is position over the view. The left mouse button rotates around the center of rotation. The center of rotation is indicated by the cross hairs in the view. You can change the center of rotation using the center of rotation toolbar. Reset puts the center of rotation in the current view. You can also select the center of rotation by selecting the pick-center-of-rotation icon. There is also an entry available to manually select the center of roation point. There are two options for rotation that depend on when you first click in the view. When you mouse near the center of rotation, you get the standard rotation around the view's X and Y axes. When you start rotation by clicking far from the center of rotation, the you get a roll behavior which is rotation around the views Z axis. For convenience, in the rotation interactor state, the right mouse button behaves like the translation interactor.

The translate interactor allows you to pan the view. Once again, its behavior depends on where you first click on the view. When you click in upper or lower thirds of the view, you get a zooming behavor which moves the view along it's Z axis. Clicking in the middle third of the view gives a paning interaction which translates the view along its X and Y axes.

# Levels of Detail

ParaView has two mode for rendering: still and interactive. The interactive mode is set when the user is interactively manipulating the view. The still mode is used for the final render after interaction has stopped.

Level of details (LOD) may be used to increase the frame rate for interactive renders. ParaView uses two LOD techniques. A decimated model can replace the full resolution model to keep the polygon count low. Also, when ParaView is rendering in parallel, pixel replication is used to reduce the cost of compositing. The application of these two techniques can be controlled fro the user interface. In the upper right toolbar contains a reduction check box and a frame rate slider.

Pixel replication is only used when the reduction box is checked. The frame rate slider determines the amount of time that is allocated for each interactive render. When the slider is all the way to the left, an unlimited amount of time is allocated, so no LOD techniques are used. When the slider is moved to the right, less time is allocated and ParaView will start using decimate models and rendering lower resolution images.

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Last modified: Mon Dec 3 13:20:36 EST 2001