Disk

Syntax:

	(disk
           (radius: number)
           (scale:  coord)
           (material: material)
           (material2: material)
           (bump-map: symbol)
           (bump-scale: number)
           (bump-frequency: number)
           (texture-frequency: number)
           (texture: symbol)
           (thickness: number)
           (center: coord)
           (name: string)
           (color: number)
           (index-of-refraction: number)
           (reflectivity: number)
           (emissivitiy: number)
           (transparency: number))

radius:

A number denoting the radius of the disk. Radii are in meters. The default radius is 1.

scale:

A set of coordinates giving the scale of each dimension (x, y, z) of the disk. The default scale is (1, 1, 1).

material:

The material of the object. See Primitive Procedures - Material for details.

material2:

The secondary material of the object. See Primitive Procedures - Material for details. This secondary material is used for texturing the plane (i.e. CHECKER or STRIPE).

bump-map:

A symbol which describes the bump-map to use on the object. Plain, wave, and ripple are available. The variables PLAIN, WAVE, and RIPPLE are bound to the symbols plain, wave and ripple. Plain is the default bump-map.

bump-scale:

A number designating how bumpy the bump-map should be. The default bump-scale is 1.

bump-frequency:

A number designating the frequency of the bump-map. The default bump-frequency is 1 wave per meter.

texture-frequency:

A number indicating the frequency of the alternation between the two surfaces. Texture-frequency is measured in squares per meter. The default texture-frequency is 1.

thickness:

A number denoting the thickness of the plane in meters. The default thickness is .1.

Note: Thickness applies only to the effect that the plane has on light rays, and does not apply to the appearance of the plane. Planes will appear infinitely thin no matter what value of thickness is specified.

texture:

A symbol designating the texture map to use on the object. Plain, checker, and stripe are available. The variables PLAIN, CHECKER and STRIPE are bound to the symbols plain, checker and stripe. The default texture is PLAIN.

thickness:

A number denoting the thickness of the disk in meters. Note: Thickness applies only to the effect that the disk has on light rays, and does not apply to the appearance of the disk. Disks will appear infinitely thin no matter what value of thickness is specified.

center:

A set of coordinates giving the position of the center of the disk in meters. The default center is at the origin, (0, 0, 0).

name:

A tag which can be added to the object for identification purposes. The default name is "Disk".

color:

A coordinate indicating the (r, g, b) value of the base color of the object. Each element is on the range {0, 1}. The default color is grey, (.5, .5, .5}.

transparency:

A number on the range {0, 1} indicating the percent loss in intensity of light per meter of material traveled through. A value of 1 results in a perfectly transparent surface, a value of 0 results in a perfectly opaque surface. The default transparency is 0, or opaque.

Note: In determining the appearance of the object, transparency is multiplied by the color. For example, an object with color (0, 0, 0) cannot be at all transparent, regardless of the transparency of the material.

emissivity:

A number on the range {0,1} indicating the emissivity of the material. A value of 1 results in a material with maximum glow; a value of 0 results in a material that does not glow. The default emissivity is 0.

index-of-refraction:

A number on the range {1,2} indicating the index of refraction of the material. The index of refraction of air is 1.0; for water it is 1.33. The default index-of-refraction is 1.2.

shininess

A number on the range {0,1} indicating the sharpness of the specular highlight. Shiny materials have a small, sharp highlight; matte materials have a large, dull highlight. A value of 1 indicates the highest shininess; 0 indicates the least shininess.

reflectivity:

A number on the range {0,1} indicating the reflectivity of the material. A value of 1 is a perfectly reflective material, i.e. a perfect mirror; a value of 0 is a completely dull material.

Example:

(disk (radius: .8) (center: (: 3 0 0))

This code creates a disk of radius .8 located 3 meters from the origin along the positive x-axis.