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|
local geom = {}
local function class(tbl)
setmetatable(tbl, tbl)
return tbl
end
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- point
--
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
geom.point = class{
__call = function(this, x, y)
local pt = {}
pt.x = x
pt.y = y
setmetatable(pt, {__index=this})
return pt
end,
distance_to = function(self, pt)
local d_x = self.x - pt.x
local d_y = self.y - pt.y
return math.sqrt(d_x*d_x + d_y*d_y)
end,
}
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- square
--
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
geom.square = class{
__call = function(this, center, span)
local square = {}
square.center = center
square.span = span
square.x = this.axis_range(center.x, span/2)
square.y = this.axis_range(center.y, span/2)
setmetatable(square, {__index=this})
return square
end,
axis_range = function(c, r) return {min=c-r, max=c+r} end,
-- returns true if a point is inside of the square
-- and false otherwise
-- (x/y mininum exclusive, maximum inclusive)
contains = function(self, point)
local x_overlap =
(point.x > self.x.min) and (point.x <= self.x.max)
local y_overlap =
(point.y > self.y.min) and (point.y <= self.y.max)
if x_overlap and y_overlap then
return true
end
return false
end,
-- return an array of four squares covering the same
-- area as their parent
divide = function(self)
local this = getmetatable(self).__index
local x = self.center.x
local y = self.center.y
local d = self.span / 4
return {
this(geom.point(x-d, y-d), d*2),
this(geom.point(x+d, y-d), d*2),
this(geom.point(x-d, y+d), d*2),
this(geom.point(x+d, y+d), d*2),
}
end
}
return geom
|
