Find if a point is within a triangle: Difference between revisions
Find if a point is within a triangle (view source)
Revision as of 08:36, 6 November 2021
, 2 years agoadd gwbasic
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Triangle is [[0.1 0.1111111111111111] [12.5 33.333333333333336] [-12.5 16.666666666666668]]
Point [5.414285714285714 14.349206349206348] is within triangle ? true
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=={{header|GW-BASIC}}==
<lang gwbasic>10 PIT1X! = 3 : PIT1Y! = 1.3 : REM arbitrary triangle for demonstration
20 PIT2X! = 17.222 : PIT2Y! = 10
30 PIT3X! = 5.5 : PIT3Y! = 18.212
40 FOR PITPY! = 0 TO 19 STEP 1
50 FOR PITPX! = 0 TO 20 STEP .5
60 GOSUB 1000
70 IF PITRES% = 0 THEN PRINT "."; ELSE PRINT "#";
80 NEXT PITPX!
90 PRINT
100 NEXT PITPY!
110 END
1000 REM Detect if point is in triangle. Takes 8 double-precision
1010 REM values: (PIT1X!, PIT1Y!), (PIT2X!, PIT2Y!), (PIT3X!, PIT3Y!)
1020 REM for the coordinates of the corners of the triangle
1030 REM and (PITPX!, PITPY!) for the coordinates of the test point
1040 REM Returns PITRES%: 1=in triangle, 0=not in it
1050 PITDAR! = -PIT2Y!*PIT3X! + PIT1Y!*(-PIT2X! + PIT3X!) + PIT1X!*(PIT2Y - PIT3Y!) + PIT2X!*PIT3Y!
1060 PITXXS = (PIT1Y!*PIT3X! - PIT1X!*PIT3Y! + (PIT3Y! - PIT1Y!)*PITPX! + (PIT1X! - PIT3X!)*PITPY!)/PITDAR!
1070 PITXXT = (PIT1X!*PIT2Y! - PIT1Y!*PIT2X! + (PIT1Y! - PIT2Y!)*PITPX! + (PIT2X! - PIT1X!)*PITPY!)/PITDAR!
1080 PITRES% = 0
1090 IF PITXXS!<=0 THEN RETURN
1100 IF PITXXT!<=0 THEN RETURN
1110 IF PITXXS!+PITXXT!>=1 THEN RETURN
1120 PITRES% = 1
1130 RETURN</lang>
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