draw_lines_starfield.lua

-- Starfield 3D

hg = require("harfang")

hg.InputInit()
hg.WindowSystemInit()

width, height = 1280, 720
window = hg.RenderInit('Harfang - Starfield', width, height, hg.RF_VSync | hg.RF_MSAA4X)

-- vertex layout
vtx_layout = hg.VertexLayout()
vtx_layout:Begin()
vtx_layout:Add(hg.A_Position, 3, hg.AT_Float)
vtx_layout:Add(hg.A_Color0, 3, hg.AT_Float)
vtx_layout:End()

-- simple shader program
shader = hg.LoadProgramFromFile('resources_compiled/shaders/pos_rgb')

-- initialize stars
starfield_size = 10

max_stars = 1000
vtx = hg.Vertices(vtx_layout, max_stars * 2)

stars = {}
for i = 1, max_stars do
	table.insert(stars, hg.RandomVec3(-starfield_size, starfield_size))
end

-- main loop
while not hg.ReadKeyboard():Key(hg.K_Escape) and hg.IsWindowOpen(window) do
	hg.SetViewClear(0, hg.CF_Color | hg.CF_Depth, hg.Color.Black, 1, 0)
	hg.SetViewRect(0, 0, 0, width, height)

	dt = hg.TickClock()
	dt_f = hg.time_to_sec_f(dt)

	-- update stars
	vtx:Clear()
	for i, star in ipairs(stars) do
		star.z = star.z - 2 * dt_f
		if star.z < starfield_size then
			star.z = star.z + starfield_size
		end
		vtx:Begin(2 * (i-1)):SetPos(star * hg.Vec3(1 / star.z, 1 / star.z, 0)):SetColor0(hg.Color.Black):End()
		vtx:Begin(2 * (i - 1) + 1):SetPos(star * hg.Vec3(1.04 / star.z, 1.04 / star.z, 0)):SetColor0(hg.Color.White):End()
	end

	-- draw stars as lines
	hg.DrawLines(0, vtx, shader)

	hg.Frame()
	hg.UpdateWindow(window)

	-- prevent GC bottleneck 
	collectgarbage()
end

hg.RenderShutdown()
hg.DestroyWindow(window)