To draw a line, you need two points between which you can draw a line. The Bresenham algorithm is another incremental scan conversion algorithm. The big . E Claridge, School of Computer Science, The University of Birmingham. DERIVATION OF THE BRESENHAM’S LINE ALGORITHM. Assumptions: ○ input: line. The basic ”line drawing” algorithm used in computer graphics is Bresenham’s example, in which we wish to draw a line from (0,0) to (5,3) in device space.
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Line Generation Algorithm
To draw a line, you need two points between which you can draw a line. It is a basic element in graphics. Since all of this is about the sign of the accumulated difference, then everything can be multiplied by 2 with no consequence.
This simple decision is based on the difference between the two pixel positions. The algorithm is used in hardware such as plotters and in the graphics chips of modern graphics cards. This page was last edited on 16 Octoberat In low level implementation which access the video memory directly it would be typical for the special cases of vertical and horizontal lines to be handled separately as they can be highly optimised.
This is a function of only x and it would be useful to make this equation written as a function of both x and y. Views Read Edit View history.
Bresenham’s line algorithm is an algorithm that determines the points of an n -dimensional raster that should be selected in order to form a close approximation to a straight line between two points. It is one of the earliest algorithms developed in the field of computer graphics. Bresenham’s algorithm was later extended to produce circles, the resulting algorithms being ‘Bresenham’s circle algorithm and midpoint circle algorithm.
The plotting can be viewed by plotting at the intersection of lines blue circles or filling in pixel boxes yellow squares. I happily agreed, and they printed it in You would like the point that is closer to the original line.
Bresenham’s algorithm chooses the integer y corresponding to the pixel center that is closest to the ideal fractional y for the same x ; on successive columns y can remain the same or increase by 1. The point 2,2 is on the line. Mid-point algorithm is due to Bresenham which was modified by Pitteway and Van Aken.
Remember, the coordinate changes occur along the x axis in unit steps, so you can do everything with integer calculations. August Learn how and when to remove this template message. The first step is transforming the equation of a line from the typical slope-intercept form into something different; and then using this new equation for a line to draw a line based on the idea of accumulation of algorithn.
Since we know the column, xthe pixel’s row, yis given by rounding this quantity to the nearest integer:. This observation is very important in the remainder of the derivation. A description of the line drawing routine was accepted for presentation at the ACM national altorithm in Denver, Colorado.
Bresenham’s line algorithm
In other projects Wikimedia Commons. Articles needing additional references from August All articles needing additional references All articles with algoritjm statements Articles with unsourced statements from September Articles with unsourced statements from December All Wikipedia articles needing clarification Wikipedia articles needing clarification from May Commons category link is on Wikidata Articles with example pseudocode. The voxel heightmap software-rendering engines seen in some PC games also used this principle.
The Bresenham alggorithm is another incremental scan conversion algorithm. However, as mentioned above this is only for octant zero, that is lines starting at the origin with a gradient between 0 and 1 where x increases by exactly 1 per iteration and y increases by 0 or 1.
The adjacent image shows the blue point 2,2 chosen to be on the line with two candidate points in green 3,2 and 3,3. Unsourced material may be challenged and removed.
From Wikipedia, the free encyclopedia. You can use these to make a simple decision about which pixel is closer to the mathematical line. This decision can a,gorithm generalized by accumulating the error. The result of this plot is shown to the right.
Bfesenham black point 3, 2. It is an incremental error algorithm. It is possible to use this technique to calculate the U,V co-ordinates during raster scan of texture mapped polygons [ citation needed ].
The Bresenham Line-Drawing Algorithm
This article needs additional citations for verification. If the intersection point Q is closest to the point N then N is considered as the next point; otherwise E. If it is closer to the former then include the former point on the line, if the latter then the latter. Moving across the x axis in unit intervals and at each step choose between two different y coordinates. This can be chosen by identifying the intersection point Q closest to the point N or E.
It was a year in which no proceedings were published, only the agenda of speakers and topics in an issue of Communications of the ACM. The principle of using an incremental error in place of division operations has other applications in graphics. The label “Bresenham” is used today for a family of algorithms extending or modifying Bresenham’s original algorithm.
In the following pseudocode sample plot x,y plots the pixel centered at coordinates x,y and abs returns absolute value:. By switching the x and y axis an implementation for positive or negative steep gradients can be written as. Line Generation Algorithm Advertisements.