Revision: | 1.1 |
Committed: | Sat Feb 22 02:07:21 2003 UTC (21 years, 7 months ago) by greg |
Branch: | MAIN |
CVS Tags: | rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R5, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1 |
Log Message: | Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release |
# | Content |
---|---|
1 | { |
2 | Calculate center and radius of circle based on three |
3 | points in the plane. |
4 | |
5 | Beware colinear points and points parallel to y-axis. |
6 | |
7 | 6/4/2002 Greg Ward |
8 | solution due to Paul Bourke |
9 | |
10 | Inputs: |
11 | |
12 | x1,y1,x2,y2,x3,y3 - points on circle |
13 | |
14 | Outputs: |
15 | |
16 | xc, yc, r - center and radius |
17 | } |
18 | sq(x) : x*x; |
19 | |
20 | ma = (y2-y1)/(x2-x1); |
21 | mb = (y3-y2)/(x3-x2); |
22 | |
23 | xc = (ma*mb*(y1-y3) + mb*(x1+x2) - ma*(x2+x3)) / (2*(mb-ma)); |
24 | |
25 | yc = ((x1+x2)/2 - xc)/ma + (y1+y2)/2; |
26 | |
27 | r = sqrt(sq(x2-xc) + sq(y2-yc)); |