local width = 7
local height = 7
local distance = 5
local amplitude = 2
local x = 0

function getHeadsetMatrix()
    local fx, fy, fz, fangle, fax, fay, faz = lovr.headset.getPose("head")
    return lovr.math.newMat4(lovr.math.vec3(fx, fy, fz), lovr.math.vec3(1, 1, 1), lovr.math.quat(fangle, fax, fay, faz))
end

function drawGrid(pass, headMatrix)
	local offset = math.sin(x)*amplitude

	for i=-0.5,0.5,0.05 do
		local startVect = headMatrix*lovr.math.newVec3(width*-1+offset, height*i, -distance)
		local endVect = headMatrix*lovr.math.newVec3(width*1+offset, height*i, -distance)
		pass:line(startVect, endVect)
	end

	for i=-0.5,0.5,0.05 do
		local startVect = headMatrix*lovr.math.newVec3(width*i+offset, height*-1, -distance)
		local endVect = headMatrix*lovr.math.newVec3(width*i+offset, height*1, -distance)
		pass:line(startVect, endVect)
	end
end

function lovr.draw(pass)
	local headMatrix = getHeadsetMatrix()

	x = x + 0.05

	pass:setColor(0, 1, 0)
	drawGrid(pass, headMatrix)

	local center = headMatrix * lovr.math.newVec3(math.sin(x)*amplitude, 0.0, -distance)
	pass:circle(center, 0.05, 0, 0, 0, 1, 'fill')

end