Ray intersection returns ray parameter of intersection point

polygon.lua

@@ -354,7 +354,7 @@ end
 
 function Polygon:intersectsRay(x,y, dx,dy)
 	local p = vector(x,y)
-	local v = vector(dx,dy):normalize_inplace()
+	local v = vector(dx,dy)
 	local n = v:perpendicular()
 
 	local vertices = self.vertices
@@ -369,16 +369,16 @@ function Polygon:intersectsRay(x,y, dx,dy)
 			local r = q2 - p
 			local l = r:cross(w)
 			local m = v:cross(r)
-			if l >= 0 and m >= 0 and m <= det then return true end
+			if l >= 0 and m >= 0 and m <= det then return true, 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 = (q1 - p) * n
 			if dist == 0 then
-				if n:cross(q1) > 0 or n:cross(q2) > 0 then
-					return true
-				end
+				local l,m = v * (q1 - p), v * (q2 - p)
+				if l >= 0 and l >= m then return true, l end
+				if m >= 0 then return true, m end
 			end
 		end
 	end

shapes.lua

@@ -228,9 +228,17 @@ end
 -- circle intersection if distance of ray/center is smaller
 -- than radius
 function CircleShape:intersectsRay(x,y, dx,dy)
-	local n = vector(-dy,dx):normalize_inplace() -- normal vector
-	local d = vector(x,y) - self._center
-	return d * vector(dx,dy) >= 0 and (d * n) < self._radius
+	local pc = vector(x,y) - self._center
+	local d = vector(dx,dy)
+
+	local a = d*d
+	local b = 4 * d * pc
+	local c = pc * pc - self._radius * self._radius
+	local discriminant = b*b - 4*a*c
+	if discriminant < 0 then return false end
+
+	discriminant = math.sqrt(discriminant)
+	return true, math.min(-b + discriminant, -b - discriminant) / (2*a)
 end
 
 --