Shading
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Dialog Box: Shading [ Input1 Menu]

Single crystals can be shaded in color or black and white. Shading is not likely to be successful in intergrowths if one crystal hides the faces of another. Except for the illumination vector, this dialog does not apply to the 3D mode - the separate settings for that mode are in the 3D Parameters dialog in the Input2 menu.

Illumination vector . Shading is based on the cosine of the angle between the normal to the face in question and the illumination vector. This vector points toward the light source. Any units can be used when entering the vector, but it will always be normalized to length one.

Darkest shade (fraction). This option "softens" the shading by allowing the presumed illumination of the darkest zone to be other than zero. Small values of this fraction, such as 0.1 or 0.2, are usually appropriate. It is 0.0 by default.

Darkness angle (degrees). For an isolated object in a vacuum, the intensity of illumination should vary from maximum to minimum as the angle varies from 0 to 90 degrees. However, this would be a very "hard" illumination, and SHAPE allows for a "softening" or diffusing of the illumination in two alternative ways, by darkness angle or by darkest shade. The darkness angle, or the angle at which the illumination becomes zero or minimal, can vary from 90 to 180 degrees.

Color. If shading is to be shown on a 24-bit or other unrestricted device, you can select any RGB color. However, for compatibility with a range of devices it is best to use simple colors, starting with the first 8 colors (excepting black) in the standard Palette. If the face color is the same as the back edge color (Line Colors), and if back edges are enabled (Line Attributes), there may be an illusion of transparency.

Palette settings for 256-color display. SHAPE can set up the palette for 8-bit or 256-color displays in either of two ways. The primary palette (see the Palette dialog in the Settings menu) has 16 colors, which are always available for lines. Each of these, except black, can be used as the basis for 16 color zones, shading towards black; or colors 1-7 can each be used as the basis of 32 zones. If you select 16 zones, you can select any of the 15-non-black colors in the Palette with the Select Color button. If you select 32 zones, which generally gives better results for crystals with many faces, the only colors which can be shown are 0-7. If you select any of colors 8-15, they will be forced to one of the colors 0-7. Black, number 0, will not be shaded.

Multiple crystals . In many cases shading is incorrect for multiple crystals, especially for interpenetration intergrowths - the standard method of drawing is designed mainly to draw edges, not surfaces. There are liable to be problems with shading whenever the Remove Hidden Lines option (Display menu) is used. The 3D display mode avoids all problem of this sort.