1 / 17

Scan Conversion, Lines, Circles and Ellipse

Scan Conversion, Lines, Circles and Ellipse. Dr. Aree Ali Mohammed Assistant Professor 2014-2015 3 rd Stage aree.ali@univsul.edu.iq. Constructing 2D Objects in Computer Graphics. Points. Polygone. Line. Rectangle. Square. Triangle. r. Ellipse. (0, 0). C ircle. Curve.

alden-greene
Download Presentation

Scan Conversion, Lines, Circles and Ellipse

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Scan Conversion,Lines, Circles and Ellipse Dr. Aree Ali Mohammed Assistant Professor 2014-2015 3rdStage aree.ali@univsul.edu.iq University of Sulaimani – Computer Science Dept.

  2. Constructing 2D Objects in Computer Graphics Points Polygone Line Rectangle Square Triangle r Ellipse (0, 0) Circle Curve

  3. Constructing 3D Objects in Computer Graphics

  4. Scan Conversion or Rasterization • Drawing lines, circles, and etc. on a grid implicitly involves approximation. • The general process: Scan Conversion or Rasterization • Ideally, the following properties should be considered • smooth • continuous • pass through specified points • uniform brightness • efficient

  5. Line Drawing Algorithms

  6. Line Drawing Algorithms

  7. Line Drawing Algorithms

  8. Line Drawing Algorithms

  9. DDA - Line Drawing Algorithms

  10. DDA - Line Drawing Algorithms

  11. DDA - Line Drawing Example

  12. Bresenham’s Line Algorithm

  13. Bresenham’s Line – Example

  14. Review Questions and Homework • Explain the steps in the incremental line drawing algorithm. • Explain the steps in DDA line drawing algorithm. • Explain the steps in Bresenham’s line drawing algorithm. • HW/ • Draw the following lines using DDA and Bresenham: •  (from left to right): •  (-1, 2) and (7, 8) •  (1, -3) and (6, 5) •  (from right to left) •  (6, 2) and (-4, -3) •  (9, 4) and (2, -5)

  15. Scan Converting CirclesExampl Midpoint Circle Algorithm 1. Input radius r and circle center (xc,yc) and obtain the first point on the circumference of the circle centered on the origin as (x0, y0) = (0, r) 2. Calculate the initial value of the decision parameter as Po=5/4-r or [po=1-r for r an integer] 3. At each xk position starting at k = 0 , perform the following test. If pk < 0 , the next point along the circle centered on (0, 0) is (xk+1, yk) and pk+1 = pk + (2xk+1) + 1 Otherwise the next point along the circle is (xk+1, yk-1) and pk+1 = pk + (2xk+1) + 1 – (2yk+1) Where 2xk+1 = 2xk+2 and 2yk+1 = 2yk – 2 4. Determine symmetry points in the other seven octants 5. Move each calculated pixel position (x,y) onto the circular path centered on (xc, yc) and plot the coordinate values x = x+ xc , y= y+ yc 6. Repeat steps 3 through 5 until x >= y

  16. Scan Converting CirclesExampl Scan Converting Circle - Example

  17. Reading List • “Computer Graphics with OpenGL” , chapter 3. • Raster versus Vector http://www.sketchpad.net/basics1.htm

More Related