Solid Area Scan Conversion in computer graphics

The main reason for the rapid increase in popularity of raster scan displays is their ability to display “solid” images. They are useful in representative, thickness, depth, or objects line up one behind another. Needless to say, the ability to display the third dimension is of prime importance in realistic display of objects, especially in video games and animation.

Generating a display of a solid object means one should be able to

  • Find out pixels that lie within the solid area and find out those that lie outside the solid area. This concept is called the mask of the area. One simple way of representative such pixels is to use a 1 to indicate pixels that lie inside the area and use a 0 to indicate pixels outside. The bit is called the “mask”
  • To determine the shading rule. The shading rule deals with the pixel intensity of each pixel within the solid area. To give a realistic image for the depth, it is essential that the “shade” of each pixel be indicated separately, so as to give a coherent idea of the concept of depth. Such a mechanism would give the effect of shadows to pictures so that pixels that lie nearer to the observer would caste a shadow on those that are far away. A variable shading technique is of prime importance in presenting realistic 3- dimensional pictures
  • To determine the priority. When one speaks of 3-dimensions and a number of objects, the understanding is that some of the objects that are nearer are likely to cover the objects that are far away. Since each pixel can represent only one object, the pixel should become a part of the object that is nearest to the observer i.e. a priority is assigned to each object and if a pixel forms part of more than one object, then it will represent the object with the highest priority amongst them

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