The SEDRIS Data Representation Model
APPENDIX C - Types
SE_Colour_Mapping
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/*
* ENUM: 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>) is being coloured.
*
* 2. A Primary Colour is the main colour of the object, when the object's
* appearance is not affected by texture maps or viewing distance
* (that is, distance from the observer to the object).
*
* Note that an <Image>'s alpha (if any), and/or a colour's alpha
* (a.k.a. <Translucency>) 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 Level Of
* Detail Data> (i.e., distance from the viewer) in <Level Of Detail
* Related> 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> and 2) an <Image Mapping Function>, the
* image_mapping_method of which is set to blending.
* a) If the <Image> is an intensity <Image> (i.e., LUMINANCE is part of
* its signature), then 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>. That is, for an <Image> with a LUMINANCE or
* LUMINANCE_AND_ALPHA image_signature, the image blend
* and primary colours are linearly combined with the <Image>'s
* luminance and its inverse to determine the displayed luminance.
* Where the <Image> is bright, its colour combined with that of the
* object's Image Blend Colour will dominate. Where the <Image> is dark,
* the object's Primary Colour will dominate.
* b) If the <Image> is a 123COLOUR <Image> or some variation thereof, the
* 1st, 2nd, and 3rd colour components of each texel (e.g. R, G, B) are
* linearly interpolated between the PRIMARY_COLOUR and the
* IMAGE_BLEND_COLOUR. That is, for an <Image> with image_signature =
* 123COLOUR or 123COLOUR_ALPHA, the image blend and primary colours
* are linearly combined with the <Image>'s colour and its inverse to
* determine the displayed colour. Where the <Image> is bright, its
* colour combined with that of the object's image blend colour will
* dominate. Where the <Image> is dark, the object's primary colour
* will dominate.
*
* See also SE_Image_Mapping_Method for further discussion of blending.
*/
} SE_Colour_Mapping;
Enumerant Notes
The Primary Colour of an object's <Light Rendering Behaviour>.
It cannot be combined with any other colour mapping.
The Secondary Colour of an object's <Light Rendering Behaviour>.
It cannot be combined with any other colour mapping.
Prev: SE_Colour_Data.
Next: SE_Colour_Model.
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Last updated: May 15, 2003
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Copyright © 2003 SEDRIS
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