/*
 * SET: SE_Colour_Mapping
 *
 *   This data type specifies how the given <Colour> instance is applied
 *   to the objects that reference it.
 *
 *   1. "Front" and "back" refer to which side of the object (usually a
 *      <Polygon> instance) is being coloured.
 *
 *   2. A "primary colour" is the main colour of the object, when the
 *      appearance of the object is not affected by texture maps or viewing
 *      distance (that is, distance from the observer to the object).
 *
 *      Note that the alpha of an <Image> instance (if any), and/or the
 *      alpha of a <Colour> instance (a.k.a. the <Translucency> component
 *      of the <Colour> instance) are not affected by anything other
 *      than the primary colour, even when an image blend colour is present.
 *
 *   3. A "distance blend colour" is used to model the distortion of colour
 *      due to distance from the viewer. (For instance, mountains in the
 *      distance appear to be tinted blue, an effect that increases with
 *      increasing distance as long as the mountains are still visible.)
 *
 *      This is applicable mainly to objects organized by distance from
 *      the viewer - that is, by <Distance LOD Data> link objects -
 *      in level-of-detail aggregations, since the distance that the object
 *      is visible shall be finite. The equation to determine the desired
 *      component of the final displayed colour is
 *            C = PCC*((x-y)/y) + DBCC*(x/y)
 *      where
 *          x    is the distance to the object
 *          y    is the total distance that the object is visible
 *          PCC  is the colour of the PRIMARY_COLOUR <Colour> component
 *          DBCC is the colour of the DISTANCE_BLEND_COLOUR <Colour> component
 *
 *      Distance blend colour dominates more as viewing distance increases,
 *      while primary colour dominates more as viewing distance decreases.
 *
 *   4. An "image blend colour" helps determine the appearance of an object
 *      that has both 1) a <Colour> component and 2) an <Image Mapping Function>
 *      component, the image_mapping_method of which is set to blending.
 *      a) If the <Image> instance is an intensity <Image> instance (that is,
 *         LUMINANCE is part of its signature),  the intensity map is used to
 *         modulate between the PRIMARY_COLOUR and IMAGE_BLEND_COLOUR, based
 *         on the values of the texels in the <Image> instance. That is, for
 *         an <Image> instance with a LUMINANCE or LUMINANCE_AND_ALPHA
 *         image_signature, the image blend and primary colours are linearly
 *         combined with the <Image> instance's luminance and its inverse to
 *         determine the displayed luminance. Where the <Image> instance is
 *         bright, its colour combined with that of the DRM object's
 *         Image Blend Colour will dominate. Where the <Image> instance is
 *         dark, the object's Primary Colour will dominate.
 *      b) If the <Image> instance is a 123COLOUR <Image> instance or some
 *         variation thereof, the first, second, and third colour components
 *         of each texel are linearly interpolated between the PRIMARY_COLOUR
 *         and the IMAGE_BLEND_COLOUR. That is, for an <Image> instance with
 *         image_signature = 123COLOUR or 123COLOUR_ALPHA, the image blend
 *         and primary colours are linearly combined with the <Image>
 *         instance's colour and its inverse to determine the displayed
 *         colour. Where the <Image> instance is bright, its colour combined
 *         with that of the DRM object's image blend colour will dominate.
 *         Where the <Image> instance is dark, the object's primary colour
 *         will dominate.
 *
 *      See also SE_Image_Mapping_Method for further discussion of blending.
 */

Field Notes

¹ The primary colour of the <Light Rendering Behaviour> component(s) of the <Light Rendering Properties> component of a DRM object. It cannot be combined with any other colour mapping.

² The secondary colour of the <Light Rendering Behaviour> component(s) of the <Light Rendering Properties> component of a DRM object. It cannot be combined with any other colour mapping.