Table 6

Table 6.204—DRM_Primitive_Color

Property

Description

Superclass

Class

· <DRM Primitive Colour>

Subclass

· none

Definition

This is a DRM class that specifies a single colour definition, containing the individual emissive, diffuse, ambient and specular components.

The colour of an object illuminated by a light source X may be determined by combining the following:

· the <DRM Ambient Colour> with the ambient component of X,

· the <DRM Diffuse Colour> with the diffuse component of X,

· the <DRM Specular Colour> with the specular component of X,

and add any intensity due to the <DRM Emissive Colour> (not affected by X.)

Example(s)

· Consider a <DRM Geometry Model Instance> of a computer monitor, placed on top of a <DRM Geometry Model Instance> of a desk. A <DRM Positional Light> affecting the two objects is located so that the illumination is directed from above. (Assume that these instances are present within an environment simulating an ordinary room.) Each of the <DRM Polygon>s within the desk <DRM Model> have an <DRM Inline Colour> whose <DRM Primitive Colour> has both an <DRM Ambient Colour> and a <DRM Diffuse Colour> component. Due to the <DRM Diffuse Colour> component, the area of the desk under the monitor that is visible to the observer appears to be in shadow. However, the shadowy area is not totally blacked out, because the <DRM Ambient Colour> simulates the effect due to light reflected from the walls, ceiling, etc. that would reach that area.

· Consider a <DRM Line> used to simulate a line of runway lights. The <DRM Colour> of the <DRM Line> would resolve to a <DRM Primitive Colour> consisting primarily (possibly completely) of an <DRM Emissive Colour>, since the <DRM Line> is pretending to emit light.

· Consider a collection of <DRM Polygon>s used to represent the surface of a sunlit lake. The <DRM Colour>s of these <DRM Polygon>s resolve to <DRM Primitive Colour>s consisting of <DRM Ambient Colour>, <DRM Diffuse Colour>, and <DRM Specular Colour> components. The <DRM Ambient Colour> prevents any <DRM Polygon>s in shadow from appearing black, while the <DRM Diffuse Colour> provides most of the normal appearance of a lit object. However, since water is a reflective substance, its colour requires a <DRM Specular Colour> component to simulate light reflected from the water.