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
Main Objectives of this connector is to allow full duplex communication between peripherals that uses such connector such PIC Demo board, ICD2 Debugger etc. The RS32 connector pin

i need help in my Engineering graphic assignment

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

If the spacing between the knot sequence is uniformly doubled, will the shape of the resulting B-spline curve change?  Justify your answer.


What is scaling and shearing? The scaling transformations alters the shape of an object and can be carried out  by multiplying every vertex (x,y) by scaling factor Sx, Sy where

How many key frames does one minute animation film order along with no duplications need if there are five in among for each pair of key frames?   Solution : One minute = 60 sec

Image Processing Process Images are the last product of most processes in computer graphics. The ISO that is International Standards Organization explains computer graphics as

Containment Test -  visible surface detection Test: That is Containment test: it can be either comprised (contained) or surrounding polygon, if intersection test fails. The

Main Objectives: Interfacing LCD to the Micro-controller (PIC18F4520) Programming LCD by using C- language via MPLAB Sending data or command to the LCD Component