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Rename intersectionsRay. Less redundancy.

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* intersectionsRay() -> intersectionsWithRay()
* intersectsRay() uses results from intersectionsWithRay()
  (Exception: PointShape does it the other way around)
This commit is contained in:
Matthias Richter 2014-01-24 09:47:13 +01:00
parent afc917253c
commit 6bb4ba0e24
2 changed files with 32 additions and 81 deletions
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63
polygon.lua
View File

@ -419,56 +419,11 @@ function Polygon:contains(x,y)
return in_polygon
end
function Polygon:intersectsRay(x,y, dx,dy)
--local p = vector(x,y)
--local v = vector(dx,dy)
function Polygon:intersectionsWithRay(x,y, dx,dy)
local nx,ny = vector.perpendicular(dx,dy)
local wx,xy,det
local tmin = math.huge
local q1,q2 = nil, self.vertices[#self.vertices]
for i = 1, #self.vertices do
q1,q2 = q2,self.vertices[i]
wx,wy = q2.x - q1.x, q2.y - q1.y
det = vector.det(dx,dy, wx,wy)
if det ~= 0 then
-- there is an intersection point. check if it lies on both
-- the ray and the segment.
local rx,ry = q2.x - x, q2.y - y
local l = vector.det(rx,ry, wx,wy) / det
local m = vector.det(dx,dy, rx,ry) / det
if l >= 0 and m >= 0 and m <= 1 then
-- we cannot jump out early here (i.e. when l > tmin) because
-- the polygon might be concave
tmin = math.min(tmin, l)
end
else
-- lines parralel or incident. get distance of line to
-- anchor point. if they are incident, check if an endpoint
-- lies on the ray
local dist = vector.dot(q1.x-x,q1.y-y, nx,ny)
if dist == 0 then
local l = vector.dot(dx,dy, q1.x-x,q1.y-y)
local m = vector.dot(dx,dy, q2.x-x,q2.y-y)
if l >= 0 and l >= m then
tmin = math.min(tmin, l)
elseif m >= 0 then
tmin = math.min(tmin, m)
end
end
end
end
return tmin ~= math.huge, tmin
end
function Polygon:intersectionsRay(x,y, dx,dy)
--local p = vector(x,y)
--local v = vector(dx,dy)
local nx,ny = vector.perpendicular(dx,dy)
local wx,xy,det
local ts = {}
local ts = {} -- ray parameters of each intersection
local q1,q2 = nil, self.vertices[#self.vertices]
for i = 1, #self.vertices do
q1,q2 = q2,self.vertices[i]
@ -484,7 +439,7 @@ function Polygon:intersectionsRay(x,y, dx,dy)
if m >= 0 and m <= 1 then
-- we cannot jump out early here (i.e. when l > tmin) because
-- the polygon might be concave
table.insert(ts, l)
ts[#ts+1] = l
end
else
-- lines parralel or incident. get distance of line to
@ -495,9 +450,9 @@ function Polygon:intersectionsRay(x,y, dx,dy)
local l = vector.dot(dx,dy, q1.x-x,q1.y-y)
local m = vector.dot(dx,dy, q2.x-x,q2.y-y)
if l >= m then
table.insert(ts, l)
ts[#ts+1] = l
else
table.insert(ts, m)
ts[#ts+1] = m
end
end
end
@ -506,6 +461,14 @@ function Polygon:intersectionsRay(x,y, dx,dy)
return ts
end
function Polygon:intersectsRay(x,y, dx,dy)
local tmin = math.huge
for _, t in ipairs(self:intersectionsWithRay(x,y,dx,dy)) do
tmin = math.min(tmin, t)
end
return tmin ~= math.huge, tmin
end
Polygon = common_local.class('Polygon', Polygon)
newPolygon = function(...) return common_local.instance(Polygon, ...) end
return Polygon

50
shapes.lua
View File

@ -213,12 +213,12 @@ function ConvexPolygonShape:intersectsRay(x,y, dx,dy)
return self._polygon:intersectsRay(x,y, dx,dy)
end
function ConcavePolygonShape:intersectionsRay(x,y, dx,dy)
return self._polygon:intersectionsRay(x,y, dx,dy)
function ConcavePolygonShape:intersectionsWithRay(x,y, dx,dy)
return self._polygon:intersectionsWithRay(x,y, dx,dy)
end
function ConvexPolygonShape:intersectionsRay(x,y, dx,dy)
return self._polygon:intersectionsRay(x,y, dx,dy)
function ConvexPolygonShape:intersectionsWithRay(x,y, dx,dy)
return self._polygon:intersectionsWithRay(x,y, dx,dy)
end
-- circle intersection if distance of ray/center is smaller
@ -228,27 +228,7 @@ end
-- solving [with c = (cx,cy)]:
--
-- d*d s^2 + 2 d*(p-c) s + (p-c)*(p-c)-r^2 = 0
function CircleShape:intersectsRay(x,y, dx,dy)
local pcx,pcy = x-self._center.x, y-self._center.y
local a = vector.len2(dx,dy)
local b = 2 * vector.dot(dx,dy, pcx,pcy)
local c = vector.len2(pcx,pcy) - self._radius * self._radius
local discr = b*b - 4*a*c
if discr < 0 then return false end
discr = math_sqrt(discr)
local s1,s2 = discr-b, -discr-b
if s1 < 0 then -- first solution is off the ray
return s2 >= 0, s2/(2*a)
elseif s2 < 0 then -- second solution is off the ray
return s1 >= 0, s1/(2*a)
end
-- both solutions on the ray
return true, math_min(s1,s2)/(2*a)
end
function CircleShape:intersectionsRay(x,y, dx,dy)
function CircleShape:intersectionsWithRay(x,y, dx,dy)
local pcx,pcy = x-self._center.x, y-self._center.y
local a = vector.len2(dx,dy)
@ -259,9 +239,18 @@ function CircleShape:intersectionsRay(x,y, dx,dy)
if discr < 0 then return {} end
discr = math_sqrt(discr)
local s1, s2 = (discr-b)/(2*a), (-discr-b)/(2*a)
local ts, t1, t2 = {}, discr-b, -discr-b
if t1 >= 0 then ts[#ts+1] = t1/(2*a) end
if t2 >= 0 then ts[#ts+1] = t2/(2*a) end
return ts
end
return {math.min(s1, s2), math.max(s1, s2)}
function CircleShape:intersectsRay(x,y, dx,dy)
local tmin = math_huge
for _, t in ipaits(self:intersectionsWithRay(x,y,dx,dy)) do
tmin = math_min(t, tmin)
end
return tmin ~= math_huge, tmin
end
-- point shape intersects ray if it lies on the ray
@ -271,10 +260,9 @@ function PointShape:intersectsRay(x,y, dx,dy)
return t >= 0, t
end
function PointShape:intersectionsRay(x,y, dx,dy)
local px,py = self._pos.x-x, self._pos.y-y
local t = vector.dot(px,py, dx,dy) / vector.len2(dx,dy)
return {t}
function PointShape:intersectionsWithRay(x,y, dx,dy)
local intersects, t = self:intersectsRay(x,y, dx,dy)
return intersects and {t} or {}
end
--