Class

• <DRM Primitive Colour>

Superclass

• <DRM SEDRIS Abstract Base>

Subclass

• None.

Definition

An instance of this DRM class specifies a single colour, consisting of individual ambient, diffuse, emissive, and specular components.

The following steps determine the colour of an object illuminated by a light source X:

1. the <DRM Ambient Colour> with the ambient component of X,
2. the <DRM Diffuse Colour> with the diffuse component of X,
3. the <DRM Specular Colour> with the specular component of X, and
4. add any intensity due to the <DRM Emissive Colour> (which is not affected by X.)

Class diagram

Figure 6.212 — DRM_Primitive_Colour

Constraints

• Publishable Object

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 <DRM Polygon> within the desk <DRM Model> has an <DRM Inline Colour> component, which in turn has a <DRM Primitive Colour> with 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’s 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, and so on that would reach that area.

• Consider a <DRM Line> used to simulate a line of runway lights. The <DRM Line>’s <DRM Colour> 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> instances used to represent the surface of a sunlit lake. These <DRM Polygon> instances’ <DRM Colour> components resolve to <DRM Primitive Colour> instances consisting of <DRM Ambient Colour>, <DRM Diffuse Colour>, and <DRM Specular Colour> components.

  The <DRM Ambient Colour> prevents any <DRM Polygon> instances 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.