Page 123 - DCAP313_LAB_ON_COMPUTER_GRAPHICS

Unit 7: Implementation of Hidden Surface in 2D

11. A conjunction of the near polygon and the reverse polygon, called ……………. Notes
12. The line scanning algorithm reduces memory demands of storage as here it is necessary
to store only a field equal to one ……………………….. of the screen
13. The painter algorithm is suitable for more simple scenes with limited conjunctions of
objects, due to its low calculation and ……………..
14. Ray tracing is, in many ways, a standardized technique. Almost all ray tracing programs
use the same basic algorithm in one way or the other.
(a) True (b) False
15. The z-buffer serves also to accept the situation where more distant objects are drawn last
and in this way overlap objects standing closer to the observer.
(a) True (b) False

7.3 Summary

• The process of hidden surface determination is sometimes called hiding, and such an
algorithm is sometimes called a hider. The analogue for line rendering is hidden line
removal. Hidden surface determination is necessary to render an image correctly.
• The Z-buffer serves also to avoid the situation where more distant objects are drawn last
and in this way overlap objects standing closer to the observer.
• A disadvantage of the Z-buffer is its memory demand. The line scanning algorithm
reduces memory demands of storage as here it is necessary to store only a field equal to
one horizontal line of the screen.
• The painter algorithm is suitable for more simple scenes with limited conjunctions of
objects, due to its low calculation and memory demands.
• Ray tracing programs use the same basic algorithm in one way or the other.

7.4 Keywords

Pixel: It is a physical point in a raster image, or the smallest, addressable element in a display
device.

Polygons: A polygon is traditionally a plane figure that is bounded by a closed path, composed
of a finite sequence of straight line segments.
Projection: A projection is the transformation of points and lines in one plane onto another plane
by connecting corresponding points on the two planes with parallel lines.
Raster: A scan pattern in which an area is scanned from side to side in lines from top to bottom;
also a pattern of closely spaced rows of dots that form an image.
Rendering: Rendering is the process of generating an image from a model by means of computer
programs.

7.5 Review Questions

1. What is the object space algorithm?

2. How many type visibility algorithm categorizations?
3. Write a short note on hidden surface removal algorithms.

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