![]() The Edge Table − It contains coordinate endpoints of each line in the scene, the inverse slope of each line, and pointers into the polygon table to connect edges to surfaces. Two important tables, edge table and polygon table, are maintained for this. In order to require one scan-line of depth values, we must group and process all polygons intersecting a given scan-line at the same time before processing the next scan-line. This method has a depth information for only single scan-line. It is an image-space method to identify visible surface. It reduces the speed problem if implemented in hardware.Step-2 − Process each polygon (One at a time)įor each projected (x, y) pixel position of a polygon, calculate depth z.įramebuffer (x, y) = surfacecolor (x, y) Advantages The 0 value for z-coordinate indicates back clipping pane and 1 value for z-coordinates indicates front clipping pane. The z-coordinates are usually normalized to the range. The frame buffer is used to store the intensity value of color value at each position (x, y). To override the closer polygons from the far ones, two buffers named frame buffer and depth buffer, are used.ĭepth buffer is used to store depth values for (x, y) position, as surfaces are processed (0 ≤ depth ≤ 1). It is applied very efficiently on surfaces of polygon. ![]() The depth values for a pixel are compared and the closest (smallest z) surface determines the color to be displayed in the frame buffer. In this method each surface is processed separately one pixel position at a time across the surface. The basic idea is to test the Z-depth of each surface to determine the closest (visible) surface. When we want to display a 3D object on a 2D screen, we need to identify those parts of a screen that are visible from a chosen viewing position. The Object-space method is implemented in physical coordinate system and image-space method is implemented in screen coordinate system. There are two approaches for removing hidden surface problems − Object-Space method and Image-space method. The identification and removal of these surfaces is called Hidden-surface problem. We must remove these hidden surfaces to get a realistic screen image. When we view a picture containing non-transparent objects and surfaces, then we cannot see those objects from view which are behind from objects closer to eye.
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