Colouring

The use of colours in CAD/CAM has two main objectives : facilitate creating geometry and display images. Colours can be used in geometric construction. In this case, various wireframe, surface, or solid entities can be assigned different colours to distinguish them. Colour is one of the two main ingredients (the second being texture) of shaded images produced by shading algorithms. In some engineering applications such as finite element analysis, colours can be used effectively to display contour images such as stress or heat-flux contours. 

Black and white raster displays provide achromatic colours while colour displays (or television sets) provide chromatic colour. Achromatic colors are described as black, various levels of gray (dark or light gray), and white. The only attribute of achromatic light is its intensity, or amount. A scalar value between 0 (as black) and 1 (as white) is usually associated with the intensity. Thus, a medium gray is assigned a value of 0.5. For multiple-plane displays, different levels (scale) of gray can be produced. F