SAS/SPECTRAVIEW Software User's Guide

Rendering a Volume and Saving as a Two-Dimensional Image

Direct-volume rendering creates a two-dimensional image of the entire volume of data points with transparency displayed in the Volume window, which you can then save to a file.

You can render an image using either the [Splat] option or the [Scanline] option:

[Splat] renders each response value using a technique that is much like splatting a snowball against the cutting plane as it moves through the volume grid.

[Scanline] renders the image or images displayed in the Volume window as a high-quality, three-dimensional image.

Note that before rendering, consider changing the size of the Volume window so that the resulting image is larger or smaller. For example, for many data points, reducing the window size improves rendering time, whereas increasing the window size can provide a better view of dense data. For instructions, see Resizing the Display Windows.

Requesting Splat Rendering

Specifying the Splat option renders each response value using a technique that is much like splatting snowballs against the cutting plane as it moves through the volume grid...each data point is a snowball. You have the option of setting an opacity degree and a splat width.

To create a splat rendered image:

Select [Tools], then [Render].
In the Opacity window, which is located at the bottom of the interface, adjust the opacity line to specify a degree of opacity or transparency for response values with the various color ranges. That is, visibility of data points in the rendered image is determined by the location of the opacity line corresponding to the colors of the data points.
To adjust the opacity degree, use the cursor to drag portions of the opacity line to the top or bottom of the window:
- Colors represented on the line at the top of the window are rendered with a high opacity, making the colored data points more opaque (clearly visible in the rendered image). To make a specific range of responses more visible in the rendered image, drag those colors to the top of the window.
- Colors represented on the line at the bottom of the window are rendered with a low opacity, making the colored data points more transparent (invisible in the rendered image). To exclude responses from the rendered image, drag those colors to the bottom of the window.
Note that you can reset the opacity line to its default degrees by selecting the Reset global button, then the All button. However, the All button resets the entire software to its defaults, so use it cautiously.
To set the size of the rendered data points, which determines how solid the rendered image is to be, adjust the splat width by dragging the slider to the right for a larger width or to the left for a smaller width. The larger the splat width, the more solid the resulting image.
Select [Splat] to initiate the rendering process.
Once the image is rendered, you are prompted to enter a filename in the text window. The file type depends on the specification from the Save global button. The default is a TIFF file.
To bypass the filename prompt or to clear the rendered image, press Enter.

Splat Rendered Image

[IMAGE]

Note that when you request splat rendering, the software renders all response values even if you have a subset of response values displayed in a point cloud.

Requesting Scanline Rendering

Specifying the scanline option renders the image displayed in the Volume window as a shaded, solid object, showing the effects of a light source. An isosurface and cutting planes are rendered as solid, Gouraud-shaded images.

For example, if you request an isosurface, rendering it using scanline produces a solid image from the wireframe one, which will show more clearly how the surface changes. In addition, a scanline rendering of a cutting plane is smoother.

To create a scanline rendered image:

Use a visualization technique to display an image or images in the Volume window, for example a point cloud.
Select [Tools], then [Render].
Select [Scanline] to initiate the rendering process.
Once the image is rendered, you are prompted to enter a filename in the text window. The file type depends on the specification from the Save global button, with the default being a TIFF file.
To bypass the filename prompt or to clear the rendered image, press Enter.

Scanline Rendered Image

[IMAGE]

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[Splat]	renders each response value using a technique that is much like splatting a snowball against the cutting plane as it moves through the volume grid.
[Scanline]	renders the image or images displayed in the Volume window as a high-quality, three-dimensional image.