Lecture 4 Graphic Primitives, Circle. Drawing Circles.
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Transcript of Lecture 4 Graphic Primitives, Circle. Drawing Circles.
Lecture 4Graphic Primitives, Circle
Drawing Circles
Brute Force Method
Cheating with 8 arcs
Cheating with 8 arcs Implementation
Cheating with 8 arcs Implementation
Digital Differential Analysis - An incremental algorithm
• Does not require sine or cosine table. • based upon calculating the gradient of a circle at a point
and using that to approximate the position of the next point.
Digital Differential Analysis - An incremental algorithm
Digital Differential Analysis - Implementation
Bresenham’s algorithm for circles• Based on limiting the choice of the next pixel to be plotted
to two alternatives, then creating and testing a decision variable to determine which alternative is actually plotted.
• D(Si) and D(Ti) represent the differences between the squared distance between the center of the circle and the middle of pixels S and T . Whichever is smallest corresponds to the pixel that should be plotted.
• To combine the two calculations into one “decision variable” is simply a matter of subtracting the two expressions:
Bresenham’s algorithm for circles
Implementation for Bresenham’s algorithm
Implementation for circles
Implementation for circles
Implementation for circles