collision.lua

local collision = {}

collision.minDistPointToSegment = function(x,y, x0,y0,x1,y1)
	-- http://www.exaflop.org/docs/cgafaq/cga1.html
	local l = vector.lenFromTo(x0,y0,x1,y1)
	local r = ((y0-y)*(y0-y1)-(x0-x)*(x1-x0)) / (l*l)
	
	--~ print(x,y, x0,y0,x1,y1,"r",r)
	
	-- clamp to end points
	if r < 0 then r = 0 end
	if r > 1 then r = 1 end
	
	local px = x0 + r * (x1 - x0)
	local py = y0 + r * (y1 - y0)
    
    return vector.lenFromTo(x,y,px,py)
end


-- x,y cone start, dx,dy cone direction, cx,cy destination to hit
collision.isUnlimitedConeHittingXY = function(x,y,dx,dy,cx,cy,coneDeltaRadians)
    local dcx,dcy = vector.fromTo(x,y, cx,cy)
    -- early out if same point
    if (vector.len(dcx,dcy) < 0.001) then return true end
    local angle = vector.angleFromTo(dcx,dcy, dx,dy)
    return angle <= coneDeltaRadians
end

-- x,y cone start, dx,dy is cone direction, range is cone range, f (x,y,width,height) is aabb
collision.isConeHittingAABB = function(x,y,dx,dy,range,f,coneDeltaRadians)
    local minDist = collision.minDistPointToAABB (x,y, f.x, f.y, f.x+f.width, f.y+f.height)
    if minDist > range then return false end

    -- corners
    if collision.isUnlimitedConeHittingXY(x,y, dx,dy, f.x,f.y, coneDeltaRadians) then return true end
    if collision.isUnlimitedConeHittingXY(x,y, dx,dy, f.x+f.width,f.y, coneDeltaRadians) then return true end
    if collision.isUnlimitedConeHittingXY(x,y, dx,dy, f.x+f.width,f.y+f.height, coneDeltaRadians) then return true end
    if collision.isUnlimitedConeHittingXY(x,y, dx,dy, f.x,f.y+f.height, coneDeltaRadians) then return true end
    -- center
    if collision.isUnlimitedConeHittingXY(x,y, dx,dy, f.x+f.width/2,f.y+f.height/2, coneDeltaRadians) then return true end

    return false
end

-- returns dist
collision.minDistPointToAABB = function(x,y, x0,y0,x1,y1)
	-- inside?
	if x0 < x and x < x1 and y0 < y and y < y1 then return 0 end
	
	local l = math.min(
		vector.lenFromTo(x,y,x0,y0),
		vector.lenFromTo(x,y,x1,y0),
		vector.lenFromTo(x,y,x0,y1),
		vector.lenFromTo(x,y,x1,y1),
		collision.minDistPointToSegment(x,y,x0,y0,x1,y0),
		collision.minDistPointToSegment(x,y,x0,y1,x1,y1),
		collision.minDistPointToSegment(x,y,x0,y0,x0,y1),
		collision.minDistPointToSegment(x,y,x1,y0,x1,y1)
	)
	
	--~ print(x,y, x0,y0,x1,y1,"->",l)
	
	return l
end

return collision