Embed Size (px)
Citation preview
1
Image Buffersand
Scan Conversion
CS-184: Computer Graphics
Prof. James O’Brien
Overview
� The frame buffer� Continuous versus discrete representations� Straight lines� Curves� Filled Polygons� Filling Algorithms
Image Buffers
� Chunk of memory to hold an image� Image made of pixels (finite area!)� Pixels have variable semantics
– RGB, gray-scale, depth, others...
� May be mapped to special hardware
Frame Buffer
Efficiency Issues
� Nice OO code helps avoid bugs� Indexing can be expensive� Out of order access may cause excess paging� Hardware often requires odd mappings
Continuous versus Discrete
2
Continuous versus Discrete Continuous versus Discrete
� Pixels have finite size� Approximate desired locations
Straight Lines Straight Lines
Straight Lines
Note: Simplified version of algorithm... see text.
3
4
5
Straight Lines
� Bresenham method much faster than DDE� Does not suffer from float problems
� Can do similar for other primitives
Curves
Approximate curves with line segments
Filled Polygons Filled Polygons
Filled Polygons Filled Polygons
6
Filled Polygons Filled Polygons
Filled Polygons Filled Polygons
Filled Polygons
� Implement with
– Test in scanning code
– Tagging edges
– Adjusting vertex locations ( why a good option? )
– Others...
Filled Polygons
7
Filled Polygons Filled Polygons
Filled Polygons
Self-intersecting polygons
A polygon
Result from non-zero winding number test
Result from parity test
Flood Fill (paint bucket)
� Fill in pixels inside some boundary
8
Neighbors and Spans
