Ray-casting algorithm: Difference between revisions

Line 3,624:

<lang rexx>/*REXX program verifies if a horizontal ray from point P intersects a polygon. */

call points 5 5, 5 8, -10 5, 0 5, 10 5, 8 5, 10 10

A=2.5; B=7.5 /* ◄───── used for shorter arguments (below).*/

A= 2.5; B= 7.5 /* ◄───── used for shorter arguments (below).*/

call poly 0 0, 10 0, 10 10, 0 10 ; call test 'square'

call poly 0 0, 10 0, 10 10, 0 10, A A, B A, B B, A B ; call test 'square hole'

call poly 0 0, A A, 0 10, A B, B B, 10 10, 10 0 ; call test 'irregular'

call poly 3 0, 7 0, 10 5, 7 10, 3 10, 0 5 ; call test 'hexagon'

exit /*stick a fork in it, we're all done. */

exit 0 /*stick a fork in it, we're all done. */

/*──────────────────────────────────────────────────────────────────────────────────────*/

in$out: procedure expose point. poly.; parse arg p; #=0

in$out: procedure expose point. poly.; parse arg p; #= 0

do side=1 to poly.0 by 2; #=# +intersect(p, side); end /*side*/

do side=1 to poly.0 by 2; #= # +intersect(p, side); end /*side*/

return # // 2 /*ODD is inside. EVEN is outside.*/

/*──────────────────────────────────────────────────────────────────────────────────────*/

intersect: procedure expose point. poly.; parse arg ?,s; sp=s + 1

intersect: procedure expose point. poly.; parse arg ?,s; sp= s + 1

epsilon= '1e' || (-digits() %~~2); infinity= "1e" || (digits()~~ *2)

epsilon= '1e' || (-digits() % 2)

Px=point.?.x; Ax=poly.s.x; Bx=poly.sp.x

Px= point.?.x; Ax= poly.s.x; Bx= poly.sp.x

Py=point.?.y; Ay=poly.s.y; By=poly.sp.y /* [↓] do a vertex swap*/

Py= point.?.y; Ay= poly.s.y; By= poly.sp.y /* [↓] do vertex swap.*/

if Ay>By then parse value Ax Ay Bx By with Bx By Ax Ay

if Py=Ay | Py=By then Py=Py + epsilon

if Py=Ay | Py=By then Py= Py + epsilon

if Py<Ay | Py>By | Px>max(Ax, Bx) then return 0

if Px<min(Ax, Bx) then return 1

if Ax\=Bx then red = (By-Ay) / (Bx-Ax)

else red = infinity

else red = i"1e" || (digits() *2) /* ◄─── infinity.*/

if Ax\=Px then return (Py-Ay) / (Px-Ax) >= red

return 1

else return 1

/*──────────────────────────────────────────────────────────────────────────────────────*/

points: wx=0; wy=0; do j=1 for arg(); parse value arg(j) with xx yy

points: wx= 0; wy= 0; do j=1 for arg(); parse value arg(j) with xx yy

wx=max(wx, length(xx) ); call value 'POINT.'j".X", xx

wx= max(wx, length(xx) ); call value 'POINT.'j".X", xx

wy=max(wy, length(yy) ); call value 'POINT.'j".Y", yy

wy= max(wy, length(yy) ); call value 'POINT.'j".Y", yy

end /*j*/

call value point.0, j-1 /*define the number of points. */

Line 3,656:

/*──────────────────────────────────────────────────────────────────────────────────────*/

poly: @= 'POLY.'; parse arg Fx Fy /* [↓] process the X,Y points.*/

n=0

n= 0

do j=1 for arg(); n=n + 1; parse value arg(j) with xx yy

do j=1 for arg(); n= n + 1; parse value arg(j) with xx yy

call value @ || n'.X', xx ; call value @ || n".Y", yy

if n//2 then iterate; n=n + 1 /*Inside? Then skip this point.*/

if n//2 then iterate; n= n + 1 /*Inside? Then skip this point.*/

call value @ || n'.X', xx ; call value @ || n".Y", yy

end /*j*/

n=n + 1 /*POLY.0 is # segments(sides).*/

n= n + 1 /*POLY.0 is # segments(sides).*/

call value @ || n'.X', Fx; call value @ || n".Y", Fy; call value @'0', n

return

/*──────────────────────────────────────────────────────────────────────────────────────*/

test: say; do k=1 for point.0; w=wx + wy + 2 /*W, WX, WY ≡are various widths*/

test: say; do k=1 for point.0; w= wx + wy + 2 /*W, WX, WY ≡are various widths*/

say right(' ['arg(1)"] point:", 30),

right( right(point.k.x, wx)', 'right(point.k.y, wy), w) " is ",