FIGURE 21 Display of volume rendering in VIDA.

object can be scaled and rotated about the x y, and z axes to make animated 3D displays. Such movies can be saved as disk files for more rapid viewing via the Movie Viewer module. Volume Render uses various mathematical methods in conjunction with a ray casting algorithm to produce different visual effects. Currently included are methods to map the brightest voxel along a ray, the darkest voxel, the average of all the voxels along a ray, or gradient shading.

Surface Render is designed to create 3D shaded surface displays of structures that can be segmented by simple thresholding. 2D segmentation can be used to preprocess images to ensure that various structures within a data set can be separated by specifying simple threshold ranges. Surface Render also allows setting multiple threshold ranges to identify multiple objects within a volume so that when two or more objects are to be displayed together, each can be assigned unique colors. A movie scripting panel is available to define a sequence of frames (i.e., rotating multiple objects, turning one or another on and off, separating the objects, etc.).

The Movie Viewer uses unique techniques to rapidly display images, including movies made using modules such as Volume Render and Surface Render. Geometric relationships and/or motion (such as myocardial wall motion through a heartbeat) are perceived by viewing many frames rapidly. This module also has the capability to flip image data sets about the major axes.

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