ISRO2011-7

Question

Which of the following is true about $z$-buffer algorithm?

• A. It is a depth sort algorithm
• B. No limitation on total number of objects
• C. Comparisons of objects is done
• D. $z$-buffer is initialized to background colour at start of algorithm

Answer 1

A is definitely  not true  Z-buffer is not depth sort it is depth buffer . Painters algorithm is called depth sort or priority algorithm

B is true in Z-buffer algo total number of objects can be arbitrary large . it is only limited by computer memory

C is not true objects are not compared only depth value is comapred

D is not true z-buffer is initialize to zero the depth of back clipping plane 

screen(frame buffer is initialized to background color)

hence ans is B refer 

https://books.google.co.in/books?id=-4ngT05gmAQC&pg=PA671&lpg=PA671&dq=comparisons+of+objects+is+done+in+z-buffer+algorithm&source=bl&ots=QXMndZkxra&sig=HcfsOws81klvkm2oBVbv7hMXzrg&hl=en&sa=X&ved=0ahUKEwiDk7Kdh4bRAhUGSY8KHf-gAjUQ6AEIRTAH#v=onepage&q=comparisons%20of%20objects%20is%20done%20in%20z-buffer%20algorithm&f=false

Comments

z buffer is initilized to infinity i guess? then the depths of each pixel of the polygon are compared with the values.

Answer 2

Answer : It is a depth Sort algorithm .I don't know much about it .So i can't tell you the details .You can refer it if you want to learn more about it.

Reference :: http://www.tutorialspoint.com/computer_graphics/visible_surface_detection.htm

Answer 3

Answer is D).

z buffer is a depth buffer algorithm in which it is initialized to background colour at the start .

It is used for hidden surface elimination.

Answer 4

It should be A , not D. Primary purpose is to determine visual surface first and then remove background hidden surface.

http://whatis.techtarget.com/definition/z-buffering