# smooth.ludic — a synthetic 2 km test ground for the terrain renderer.
#
# The valley scene stands on a real survey (Copernicus GLO-30 resampled to a 4 m grid),
# which carries its own resampling lattice and quantisation. This scene carries none:
# the height field is an analytic function (see SMOOTH in heightgen.frag), so anything
# that still looks like a grid here belongs to the renderer, not the data.
#
#   bin/ludic build examples/rendering/smooth.ludic && ./build/smooth
program Smooth {
  import "ludic.render3d/r3d.ludic"

  property Marker { on: int = 1 }
  model Anchor { Marker }

  var frame: int = 0
  var shot_at: int = 40
  var walk: bool = false
  var spin: bool = false
  var l_blades: Layer = null
  var l_grass_a: Layer = null
  var l_grass_b: Layer = null
  var s_blades: Stream = null
  var s_cards_a: Stream = null
  var s_cards_b: Stream = null
  var l_trees: Layer = null

  function rnd() -> int { return fr(rng_range(0, 9999), 10000) }
  function rnd_range(a: int, b: int) -> int { return f_lerp(a, b, rnd()) }
  function smooth(a: int, b: int, x: int) -> int {
    let t = f_clamp(f_div(f_sub(x, a), f_sub(b, a)), F_ZERO, F_ONE)
    return f_mul(f_mul(t, t), f_sub(fi(3), f_mul(F_TWO, t)))
  }
  function slope_at(x: int, z: int) -> int {
    let e = F_TWO
    let dx = f_sub(terrain_height(f_add(x, e), z), terrain_height(f_sub(x, e), z))
    let dz = f_sub(terrain_height(x, f_add(z, e)), terrain_height(x, f_sub(z, e)))
    let ny = f_div(fi(4), f_sqrt(f_add(f_add(f_mul(dx, dx), f_mul(dz, dz)), fi(16))))
    return f_sub(F_ONE, ny)
  }
  function noise01(x: int, z: int, scale: fixed) -> int {
    let n = Noise.fbm2(f_fx(x) * scale, f_fx(z) * scale, 4)
    return fl(n * 0.5 + 0.5)
  }

  # grass only where the ground is grassy: gentle, above the water, below the mountain
  function stream_fill(s: Stream, cx: int, cz: int, band: int) -> void {
    seed((cx * 73856093) ^ (cz * 19349663) ^ (band * 83492791) ^ (s.kind * 2654435761))
    let size = s.size
    let x0 = f_mul(fi(cx), size);  let z0 = f_mul(fi(cz), size)
    # Candidate spacing. These are metres between attempts, so halving one quadruples the
    # work and the instance count: the first pass here was dense enough to bury the scene
    # and cost most of the frame. Blades are only placed close to the eye, where they read
    # as individual grass; past that the cards carry the cover.
    var step = fl(1.0)
    if s.kind == 0 { if band == 0 { step = fl(0.22) } else if band == 1 { step = fl(0.45) } else { step = fl(1.1) } }
    else { if band == 0 { step = fl(0.9) } else if band == 1 { step = fl(1.8) } else { step = fl(4.0) } }
    var z = z0
    while f_ls(z, f_add(z0, size)) {
      var x = x0
      while f_ls(x, f_add(x0, size)) {
        let px = f_add(x, f_mul(rnd(), step))
        let pz = f_add(z, f_mul(rnd(), step))
        let h = terrain_height(px, pz)
        # Grassy ground only: above the water, off the steep parts, below the rim. Every
        # test is a smooth ramp — a hard height cut carves the cover into contour rings,
        # because the cut lands on a line of constant elevation.
        var keep = smooth(fl(0.2), fl(1.6), h)                       # out of the water
        keep = f_mul(keep, smooth(fi(90), fi(45), h))                # below the mountain
        keep = f_mul(keep, smooth(fl(0.42), fl(0.16), slope_at(px, pz)))
        keep = f_mul(keep, f_add(fl(0.25), f_mul(fl(0.9), noise01(px, pz, 0.02))))
        keep = f_mul(keep, fl(0.75))
        var sc = rnd_range(fl(0.16), fl(0.4))
        if s.kind != 0 { sc = f_mul(rnd_range(fl(1.5), fl(2.5)), f_add(F_ONE, f_mul(fl(0.5), fi(band)))) }
        if f_ls(rnd(), keep) {
          stream_emit(s, px, f_sub(h, fl(0.03)), pz, sc, f_mul(rnd(), f_mul(F_TWO, F_PI)), rnd(), rnd_range(fl(0.6), F_ONE))
        }
        x = f_add(x, step)
      }
      z = f_add(z, step)
    }
  }

  function scene_draw() -> void { scatter_draw() }
  function scene_draw_casters() -> void { scatter_draw_casters(shadow_cascade_vp(sh_cascade)) }

  handler Boot phase Start {
    spawn Anchor {}
    # 2 km square, generated analytically
    TERRAIN_HALF = 1000
    ter_smooth = true
    if not r3d_init(1920, 1080, "Smooth") { quit() }
    walk = Os.has_env("R3D_WALK")
    spin = Os.has_env("R3D_SPIN")
    if Os.has_env("R3D_SHOT") { shot_at = Text.to_int(Os.env("R3D_SHOT")) }

    var cx = fi(0);  var cz = fi(260)
    if Os.has_env("R3D_CAM_X") { cx = fi(Text.to_int(Os.env("R3D_CAM_X"))) }
    if Os.has_env("R3D_CAM_Z") { cz = fi(Text.to_int(Os.env("R3D_CAM_Z"))) }
    var ch = fl(1.8);  var cp = f_neg(fi(3));  var cy = fi(180)
    if Os.has_env("R3D_CAM_H") { ch = fi(Text.to_int(Os.env("R3D_CAM_H"))) }
    if Os.has_env("R3D_CAM_PITCH") { cp = fi(Text.to_int(Os.env("R3D_CAM_PITCH"))) }
    if Os.has_env("R3D_CAM_YAW") { cy = fi(Text.to_int(Os.env("R3D_CAM_YAW"))) }
    cam_set(cx, f_add(terrain_height(cx, cz), ch), cz, cy, cp)

    # a small pond in the middle of the meadow — the plane self-clips to the basin, so
    # its extent only has to cover the hollow, not the map
    water_init(fl(4.0), F_ZERO, F_ZERO, fi(200), fi(200))
    sky_set_yaw(f_rad(fi(120)))

    # grass: blades underfoot, cards beyond
    let dir = r3d_assets + "/models/grass_medium_01"
    let ga = gltf_load(dir, "grass_medium_01_1k.gltf", "grass_medium_01_tall_a_LOD0")
    let gb = gltf_load(dir, "grass_medium_01_1k.gltf", "grass_medium_01_mid_a_LOD0")
    if ga == null or gb == null { print("smooth: no grass models");  return }
    # blades are the expensive layer: keep them near, and cap them low
    l_blades = layer_new(model_blade(), 400000, true, fl(3.0), F_ZERO, fi(70))
    l_blades.blade = true
    l_grass_a = layer_cards(ga, 200000, fl(0.3), fi(260))
    l_grass_b = layer_cards(gb, 200000, fl(0.3), fi(260))
    v3_set(l_grass_a.tint, fl(0.95), F_ONE, fl(0.85))
    v3_set(l_grass_b.tint, fl(0.9), fl(0.98), fl(0.8))
    l_grass_a.rough = fl(1.6);  l_grass_b.rough = fl(1.6)
    s_blades = stream_new(l_blades, fi(8), fi(60), fi(12), fi(28), fi(60), fi(60))
    s_cards_a = stream_new(l_grass_a, fi(32), fi(240), fi(45), fi(110), fi(240), fi(240))
    s_cards_b = stream_new(l_grass_b, fi(32), fi(240), fi(45), fi(110), fi(240), fi(240))
    s_blades.kind = 0;  s_cards_a.kind = 1;  s_cards_b.kind = 2
    place_trees()
  }

  # scattered firs on the gentle ground, thinning toward the pond and the rim
  function place_trees() -> void {
    let model = gltf_load(r3d_assets + "/models/fir_tree_01", "fir_tree_01_1k.gltf", "fir_tree_01_c_LOD0")
    if model == null { print("smooth: no fir model");  return }
    l_trees = layer_new(model, 20000, false, F_ZERO, fi(90), F_ZERO)
    layer_set_impostor(l_trees, impostor_bake(model, 12, 512, 1024))
    v3_set(l_trees.tint, fl(0.9), F_ONE, fl(0.85))
    seed(4242)
    var z = f_neg(fi(900))
    while f_ls(z, fi(900)) {
      var x = f_neg(fi(900))
      while f_ls(x, fi(900)) {
        let px = f_add(x, f_mul(rnd(), fi(14)));  let pz = f_add(z, f_mul(rnd(), fi(14)))
        let h = terrain_height(px, pz)
        var keep = smooth(fi(7), fi(14), h)                 # above the pond shore
        keep = f_mul(keep, smooth(fi(120), fi(60), h))      # below the rim
        keep = f_mul(keep, smooth(fl(0.45), fl(0.2), slope_at(px, pz)))
        keep = f_mul(keep, smooth(fl(0.45), fl(0.75), noise01(px, pz, 0.004)))
        if f_ls(rnd(), f_mul(keep, fl(0.5))) {
          let sc = rnd_range(fl(0.7), fl(1.35))
          layer_add(l_trees, px, f_sub(h, fl(0.2)), pz, sc, f_mul(rnd(), f_mul(F_TWO, F_PI)), rnd(), F_ZERO)
        }
        x = f_add(x, fi(14))
      }
      z = f_add(z, fi(14))
    }
  }

  handler Fly phase Input {
    if walk { cam_move(fl(1.0), F_ZERO, F_ZERO, fl(0.003), F_ZERO);  return }
    if spin { cam_move(F_ZERO, F_ZERO, F_ZERO, fl(0.02), F_ZERO);  return }
    if not is_windowed() { return }
    Input.poll()
    var fwd = F_ZERO;  var side = F_ZERO;  var up = F_ZERO
    let speed = fl(0.6)
    if Input.key_down(key: 'w') { fwd = speed }
    if Input.key_down(key: 's') { fwd = f_neg(speed) }
    if Input.key_down(key: 'd') { side = speed }
    if Input.key_down(key: 'a') { side = f_neg(speed) }
    if Input.key_down(key: 'e') { up = speed }
    if Input.key_down(key: 'q') { up = f_neg(speed) }
    var dyaw = F_ZERO;  var dpitch = F_ZERO
    if Input.mouse_down(button: 0) {
      dyaw = f_mul(fi(Input.mouse_dx()), fl(-0.004))
      dpitch = f_mul(fi(Input.mouse_dy()), fl(-0.004))
    }
    if fwd != 0 or side != 0 or up != 0 or dyaw != 0 or dpitch != 0 { cam_move(fwd, side, up, dyaw, dpitch) }
    if Input.key_pressed(key: 'p') {
      let gy = terrain_height(cam_pos[0], cam_pos[2])
      print(`R3D_CAM_X={string(f_to_int(cam_pos[0]))} R3D_CAM_Z={string(f_to_int(cam_pos[2]))} R3D_CAM_H={string(f_to_int(f_sub(cam_pos[1], gy)))} R3D_CAM_YAW={string(f_to_int(f_mul(cam_yaw, f_div(fi(180), F_PI))))} R3D_CAM_PITCH={string(f_to_int(f_mul(cam_pitch, f_div(fi(180), F_PI))))}`)
    }
  }

  handler Draw phase Render {
    r3d_frame(fl(Time.elapsed()))
    frame += 1
    if frame == shot_at { Gl.screenshot(path: "build/smooth.ppm") }
    Gl.swap()
  }
}