Image bm829.GIF Contours
By the contours element the object surface display versus alpha component can be controlled in an active object. As the element's parameter a numeric parameter ranging between 0 and 1 is specified. Only those object surface portions are displayed the alpha component of which has a higher value than that of the parameter specified. The default setting of the contours is 0, displaying the whole object. After setting to 1 no object portion is displayed. Usualy the contours element is set to approximately 0.5. The contours are especially significant in connection with textures. Most frequently they are utilized with 2D objects as well as with static 2D objects. When drawing a texture, the object's surroundings are filled out with transparent color. This transparent color is black, its alpha component being 0. The alpha component of the other colors is 1. Thus it is secured that the texture portion having a transparent color will be suppressed (its alpha component being lower than the threshold level specified by the contours element). Only that picture portion having normal colors will be displayed. A texture can be smoothed by the smoothing of textures element. Such a texture contains also other alpha component values than 0 and 1. (This takes place on the contour transitions or on localities where color points and transparency points alternate).

Full Html Context Help of The Peter - Gemtree Software & Children Programming