Ray-casting algorithm: Difference between revisions
→{{header|Phix}}
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(8.0,5.0) IN
(10.0,10.0) OUT</pre>
=={{header|Phix}}==
<lang Phix>constant true = (1=1), false = not true
constant inf = 1e300*1e300
function rayIntersectsSegment(sequence point, sequence segment)
atom {pX,pY} = point
atom {{aX,aY},{bX,bY}} = segment
atom m_red,m_blue
-- ensure {aX,aY} is the segment end-point with the smallest y coordinate
if aY>bY then
{{bX,bY},{aX,aY}} = segment
end if
if pY=aY or pY=bY then
--
-- Consider a ray passing through the top or left corner of a diamond:
-- /
-- --- or -
-- ^ \
-- In both cases it touches both corners, but ends up outside in the
-- top case, whereas it ends up inside in the left case. Just move
-- the y co-ordinate down a smidge and it'll work properly, by
-- missing one line in the left/right cases and hitting both/none
-- in the top/bottom cases.
--
pY += 0.000001
end if
if pY<aY or pY>bY then return false end if
if pX>max(aX,bX) then return false end if
if pX<min(aX,bX) then return true end if
if aX!=bX then
m_red = (bY-aY)/(bX-aX)
else
m_red = inf
end if
if aX!=pX then
m_blue = (pY-aY)/(pX-aX)
else
m_blue = inf
end if
return m_blue >= m_red
end function
function inside(sequence point, sequence poly)
integer in = 0
for i=1 to length(poly) do
if rayIntersectsSegment(point,poly[i]) then
in = not in
end if
end for
return in
end function
constant INOUT = {"in", "out"}
function in(integer flag, integer expected)
if flag=expected then
return INOUT[2-flag]
end if
return INOUT[2-flag] & "*** ERROR ***"
end function
constant INSTAR = "* "
function instar(integer flag)
return INSTAR[2-flag]
end function
constant test_points = {{5,5},{5,8},{-10,5},{0,5},{10,5},{8,5},{10,10}}
--constant NAME = 1, POLY = 2, EXPECTED = 3
constant test_polygons = {
{"square", {{{0,0},{10,0}},{{10,0},{10,10}},{{10,10},{0,10}},{{0,10},{0,0}}},
{true,true,false,false,true,true,false}},
{"square hole", {{{0,0},{10,0}},{{10,0},{10,10}},{{10,10},{0,10}},{{0,10},{0,0}},
{{2.5,2.5},{7.5,2.5}},{{7.5,2.5},{7.5,7.5}},{{7.5,7.5},{2.5,7.5}},{{2.5,7.5},{2.5,2.5}}},
{false,true,false,false,true,true,false}},
{"strange", {{{0,5},{2.5,2.5}},{{2.5,2.5},{0,10}},{{0,10},{2.5,7.5}},{{2.5,7.5},{7.5,7.5}},
{{7.5,7.5},{10,10}},{{10,10},{10,0}},{{10,0},{2.5,2.5}}},
{true,false,false,false,true,true,false}},
{"exagon", {{{3,0},{7,0}},{{7,0},{10,5}},{{10,5},{7,10}},{{7,10},{3,10}},{{3,10},{0,5}},{{0,5},{3,0}}},
{true,true,false,false,true,true,false}}
}
sequence name, poly, expected, tp
for i=1 to length(test_polygons) do
{name,poly,expected} = test_polygons[i]
printf(1,"\n%12s:",{name})
for j=1 to length(test_points) do
tp = test_points[j]
printf(1," %s, %-4s",{sprint(tp),in(inside(tp,poly),expected[j])})
end for
end for
puts(1,"\n\n\n")
for i=0 to 10 do
for j=1 to length(test_polygons) do
puts(1," ")
poly = test_polygons[j][2]
for k=0 to 10 do
puts(1,instar(inside({k+0.5,10.5-i},poly)))
end for
end for
puts(1,"\n")
end for</lang>
{{out}}
<pre>
square: {5,5}, in {5,8}, in {-10,5}, out {0,5}, out {10,5}, in {8,5}, in {10,10}, out
square hole: {5,5}, out {5,8}, in {-10,5}, out {0,5}, out {10,5}, in {8,5}, in {10,10}, out
strange: {5,5}, in {5,8}, out {-10,5}, out {0,5}, out {10,5}, in {8,5}, in {10,10}, out
exagon: {5,5}, in {5,8}, in {-10,5}, out {0,5}, out {10,5}, in {8,5}, in {10,10}, out
********** ********** * ****
********** ********** * * ******
********** ********** * ** *******
********** *** ** * ******* ********
********** *** ** ******* **********
********** *** ** * ******** **********
********** *** ** ********** ********
********** *** ** ********** *******
********** ********** **** ******
********** ********** * ****
</pre>
=={{header|PicoLisp}}==
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