Volume Rendering

VQ offers fully 3D volume rendering, a powerful visualization tool, for all data sets. Just click on the appropriate tab (Reference, Input 1, Input 2) to edit the volume rendering for that particular data set.

Getting There

The Volume Rendering panel is available in the Tools Menu.

Another method for reaching the Volume Rendering panel is to use the keyboard shortcut "Ctrl+V". For more on keyboard shortcuts in VQ, please see Keyboard Shortcuts.

Function

Volume Rendering achieves 3D visualization by weighting voxels in a reconstruction depending on their gradient, density, and location.

The Volume Rendering panel is divided into several subregions, including Parameters, Control, and the actual Volume Rendering itself.

Volume Rendering Parameters

Option Description
Image Quality Slider bar that determines the image quality of the volume rendering. There is a tradeoff between quality of the rendering and the speed with which the rendering is accomplished.
Fog - Checkbox Enabling fog dims areas of the rendering further from the "front" as perceived by the viewer.
Fog - Base The fog base determines the overall brightness of the object. A lower base value produces a dimmer image.
Fog - Density The fog density determines the weighting of the fog as a function of the density of the object. A lower density value produces a brighter image.
Density Opacity Ramp The density opacity ramp assigns color weights to voxels depending on their density. The origin, in the bottom left of the window, represents zero opacity and the lowest density. The upper right corner of the window represents complete opacity and the highest density. The gray dots may be manipulated to assign opacity levels to different object densities. The solid lines connecting the dots indicate the density opacity function for that object. NOTE: Double-clicking on the opacity function will create another gray dot.
Gradient Opacity Ramp The gradient opacity ramp assigns color weights to regions of the object based upon the gradient of the voxel values in that region. The origin, in the bottom left of the window, represents zero opacity and the low gradients. The upper right corner of the window represents complete opacity and the highest gradients. The gray dots may be manipulated to assign opacity levels to different object gradients. The solid lines connecting the dots indicate the gradient opacity function for that object. NOTE: Double-clicking on the opacity function will create another gray dot.
Intensity The intensity of the selected data set in the volume rendering may be adjusted using this slider bar. To completely turn off the data set, select Invisible in the Image Type pulldown menu.
Image Type Three image types are available -- Luminance (default), Alpha or Opacity, and Invisible. The Luminance image is generated using a virtual light source for shading, brightness, and fog control. The Opacity image eliminates the light source, assigning voxel values based only on the density and gradient opacity ramps.
Palette The full range of color palettes is available for use in the volume rendering tool.

Volume Rendering Controls

Several controls are available for manipulating the current volume rendered image.

Option Description
Image Size Allows resizing of the image as it appears in the Volume Rendering panel. Aspect ratio is maintained.
Rotate and Axis Selection The Rotate button stops/starts rotation of the volume rendered image around the selected axis. Axis selection is possible via the drop-down menu to the right of the Rotate button.
Reset Resets the volume rendered image to its original orientation in the Volume Rendering panel.
Update Volume Rendering is a computationally-intensive process. The Update button causes the volume rendered image to be refreshed, reflecting the most recent settings in the Parameters panel. The field to the left of the Update button indicates the amount of time (in milliseconds) necessary to produce the volume rendered image.

Volume Rendered Image

The Volume Rendering tool, when properly used, can produce some striking results!

File Menu

Options are provided for saving images, saving movies, or exiting.