Z- buffer algorithm, Computer Graphics

Q. Describe the z- Buffer algorithm for hidden surface removal.

Ans. Z- buffer method: This method compares surface depths at each pixel position on the projection plane. The surface depth is measured from the view plane along the z- axis of a viewing system. When object description is converted to projection coordinates (x, y, z) each pixel position on the view plane is specified by x & y coordinate, and z value gives the depth information. Thus object depth can by comparing the z- values. The z- buffer algorithm is usually implemented in the normalized coordinates, so that z- values range from 0 at the back clipping plane to 1 at the front clipping plane. Z- Buffer Algorithm  1. Initialize the depth buffer and refresh buffer so that for all buffer position (x, y), depth (x, y) =0 refresh (x, y) = 1 background. 2. For each position on each polygon surface, compare depth values to previously started values in the depth buffer to determine visibility. (a) Calculate the depth z for each (x,y) position on the polygon. (b) If z> depth (x, y) then set depth (x, y) =z refresh (x, y) = Isuff (x, y) Where I background intensity and Isuff (x, y) is the projection intensity value for the surface at pixel position (x, y). After all surface have been processed, the depth buffer contains depth values for the visible surface and the refresh buffer contains the corresponding intensity values for those surface. In the figure, among three surface, surface S1 has the smallest depth at view position (x, y) and hence highest z value. So it is visible at that position. To calculate the z- value, the plane equation Ax + By + Cz + D = 0 is used where (x, y, z) is any point on the plane, and the coefficient A, B, C and D are contents describing the spatial properties of the plane.                                                     Only one subtraction is needed to calculate z (x + 1, y) given z (x, y), since the quotient A/C is constant and ^x = 1. A similar incremental calculation cam be performed to determine the first value of z on the next scan line, decrementing by B/C for each ^y. Drawback of z- buffer (i) It requires an additional buffer and hence the large memory. (ii) It is a time consuming process as it requires comparison for each pixel instead for the entire polygon. 



Posted Date: 7/12/2012 6:43:15 AM | Location : United States

Related Discussions:- Z- buffer algorithm, Assignment Help, Ask Question on Z- buffer algorithm, Get Answer, Expert's Help, Z- buffer algorithm Discussions

Write discussion on Z- buffer algorithm
Your posts are moderated
Related Questions

Assumption regarding to the Digital Differential Analyzer Algorithm The line generation by DDA is discussed merely for the first Quadrant, whether the line lies in the other q

1. What is the purpose behind the Staircase effect? Ans. The approximation concerned in the calculation for finding of pixel position concerned in the display of lines and th

Normal 0 false false false EN-US X-NONE X-NONE

Explain depth buffer method

Architecture: One of the purposes for the development of virtual reality (that is in fact a form of computer animation) was which it was going to be very helpful to architects. He

Q: For the following polygon, prepare an initial sorted edge list and then make the active edge list for scan lines y = 5,20,30,35 Coordinates of the vertices are as shown in Figur

Stochastic Animation - Computer Animation This utilizes stochastic processes that are a stochastic process can be identified as a random function. Such randomness could be in

What you mean by parallel projection?  Parallel projection is one in which z coordinates is discarded and parallel lines from every vertex on the object are extended unless the

Arguments made in favour of Analog Sound Shape of the waveforms: from digital signals sound reconstructed which is claimed to be harsher and unnatural compared to analog si