Find if a point is within a triangle: Difference between revisions
Find if a point is within a triangle (view source)
Revision as of 08:57, 1 November 2021
, 2 years agoadd FreeBASIC
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=={{header|FreeBASIC}}==
<lang freebasic>
type p2d
x as double 'define a two-dimensional point
y as double
end type
function in_tri( A as p2d, B as p2d, C as p2d, P as p2d ) as boolean
'uses barycentric coordinates to determine if point P is inside
'the triangle defined by points A, B, C
dim as double AreaD = (-B.y*C.x + A.y*(-B.x + C.x) + A.x*(B.y - C.y) + B.x*C.y)
dim as double s = (A.y*C.x - A.x*C.y + (C.y - A.y)*P.x + (A.x - C.x)*P.y)/AreaD
dim as double t = (A.x*B.y - A.y*B.x + (A.y - B.y)*P.x + (B.x - A.x)*P.y)/AreaD
if s<=0 then return false
if t<=0 then return false
if s+t>=1 then return false
return true
end function
dim as p2d A,B,C,P 'generate some arbitrary triangle
A.x = 4.14 : A.y = -1.12
B.x = 8.1 : B.y =-4.9
C.x = 1.5: C.y = -9.3
for y as double = -0.25 to -9.75 step -0.5 'display a 10x10 square
for x as double = 0.125 to 9.875 step 0.25
P.x = x : P.y = y
if in_tri(A,B,C,P) then print "@"; else print "."; 'with all the points inside the triangle indicated
next x
print
next y
</lang>
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