# ============================================================================
# render.ludic — the frame. Shadow cascades, the HDR scene pass (terrain, the
# scene's objects, the sky), bloom, and the tonemapped composite to the screen.
# The scene (what the game places in the world) hooks in through scene_draw /
# scene_draw_casters, which the demo defines.
# ============================================================================

var r3d_sky_prog: int = 0
var r3d_fog_density: float = 0.0
var r3d_fog_scale: float = 1.0   # float bits: a setting's multiplier over the density the day sets
var r3d_fog_falloff: float = 0.0
var r3d_fog_base: float = 0.0            # the height fog is measured from (float bits); 0 = y = 0
# Both of these are the DAY's, set by daylight_set from the sun's own elevation. The inscatter
# is how hard the air scatters the sun forward - nearly nothing at noon, and the glow a ridge
# is silhouetted against at dusk. The desaturation is how fast distance takes a surface's own
# colour away, which is the term that was missing entirely and is most of why a midday frame
# had no depth in it at all.
var r3d_fog_inscatter: float = 0.02   # 0.02, what the shader used to hard-code
var r3d_fog_desat: float = 1.35       # 1.35
# How much of the visible sky's colour comes from the analytic model rather than from the
# photograph (sky.frag). The day fades it in: at night the sky has its own tint, a star field
# and a moon, and relighting on top of those would only wash them out.
var r3d_sky_relight: float = 0.0
# What the ground reflects back up, low and high, and the height they cross at. The defaults
# are Maroon Lake's - a green basin under a grey-rock treeline at about 480 m over the datum.
var r3d_ground_alb_r: float = 0.3;  var r3d_ground_alb_g: float = 0.34;  var r3d_ground_alb_b: float = 0.14
var r3d_ground_hi_r: float = 0.289;  var r3d_ground_hi_g: float = 0.28;  var r3d_ground_hi_b: float = 0.26
var r3d_ground_hi_y: float = 480.0    # 480
var r3d_ground_hi_w: float = 150.0    # 150
var r3d_time: float = 0.0
var r3d_ready: bool = false
# set before r3d_init to build the landscape from a real height map
var r3d_dem_path: string = null
var r3d_dem_min: float = 0.0
var r3d_dem_max: float = 0.0
var r3d_dem_base: float = 0.0
var r3d_dem_ox: float = 0.0
var r3d_dem_oz: float = 0.0
var r3d_ortho_path: string = null
# A plate: no terrain, no grass, no water - the sky, the sun, the shadows and whatever the scene
# draws (a lab's stage, ludic.lab). Set before the load; nothing of the landscape is made, so
# its hundreds of megabytes of height field, materials and grass never exist.
var r3d_plate: bool = false
function r3d_plate_mode(on: bool) -> void { r3d_plate = on }
# the sky's HDR image, when it is not the default photograph under r3d_assets
var r3d_sky_path: string = null
var r3d_debug: bool = false
var r3d_debug_shadow: bool = false
var r3d_debug_max: bool = false

var r3d_cloud_shadow: float = 0.5     # 0.5

var r3d_clip_y: float = -2147483600.0            # -2^31: no clipping
# R3D_NOPREPASS=1: light the foliage the old way, every card behind the front one included
var r3d_prepass_env: int = -1
function r3d_prepass_off() -> bool {
  if r3d_prepass_env < 0 { r3d_prepass_env = 0;  if r3d_env_has("R3D_NOPREPASS") { r3d_prepass_env = 1 } }
  return r3d_prepass_env == 1
}
function fog_bind(prog: int) -> void {
  u_f(gpu_uniform(prog, "u_clip_y"), r3d_clip_y)
  u_f(gpu_uniform(prog, "u_spec_scale"), 1.0)
  u_f(gpu_uniform(prog, "u_fog_density"), r3d_fog_density)
  u_f(gpu_uniform(prog, "u_fog_height_falloff"), r3d_fog_falloff)
  u_f(gpu_uniform(prog, "u_fog_base"), r3d_fog_base)
  u_f(gpu_uniform(prog, "u_fog_inscatter"), r3d_fog_inscatter)
  u_f(gpu_uniform(prog, "u_fog_desat"), r3d_fog_desat)
  u_f3(gpu_uniform(prog, "u_ground_alb"), r3d_ground_alb_r, r3d_ground_alb_g, r3d_ground_alb_b)
  u_f3(gpu_uniform(prog, "u_ground_alb_hi"), r3d_ground_hi_r, r3d_ground_hi_g, r3d_ground_hi_b)
  u_f(gpu_uniform(prog, "u_ground_hi_y"), r3d_ground_hi_y)
  u_f(gpu_uniform(prog, "u_ground_hi_w"), r3d_ground_hi_w)
  var cs = r3d_cloud_shadow
  if r3d_env_has("R3D_NOCLOUD") { cs = 0.0 }
  u_f(gpu_uniform(prog, "u_cloud_shadow"), cs)
  u_f(gpu_uniform(prog, "u_time"), r3d_time)
}

# profiling switches (environment): R3D_NOSHADOW R3D_NOGI R3D_MSAA=n R3D_NOBLADES R3D_NOCARDS R3D_NOTREES R3D_NEAR=m
var r3d_test_frame: int = 0
var r3d_test_resize: int = 0
var r3d_no_shadow: bool = false
var r3d_no_trees: bool = false
var r3d_no_refl: bool = false
function r3d_env_flags() -> void {
  r3d_no_shadow = r3d_env_has("R3D_NOSHADOW")
  r3d_no_trees = r3d_env_has("R3D_NOTREES")
  r3d_no_refl = r3d_env_has("R3D_NOREFL")
  if r3d_env_has("R3D_DEBUG") { r3d_debug = true }
  if r3d_env_has("R3D_DBGSHADOW") { r3d_debug_shadow = true }
  if r3d_env_has("R3D_NOGI") { post_gi_strength = 0.0;  post_ao_strength = 0.0;  post_no_gi = true }
  if r3d_env_has("R3D_MSAA") { post_ms_samples = Text.to_int(r3d_env("R3D_MSAA")) }
  sc_skip_blade = r3d_env_has("R3D_NOBLADES")
  sc_skip_card = r3d_env_has("R3D_NOCARDS")
  sc_dbg_lod = r3d_env_has("R3D_LODDBG")
  if r3d_env_has("R3D_ANISO") {
    let a = Text.to_int(r3d_env("R3D_ANISO"))
    tex_anisotropy = 1.0
    if a >= 2 { tex_anisotropy = 2.0 }
    if a >= 4 { tex_anisotropy = 4.0 }
    if a >= 8 { tex_anisotropy = 8.0 }
    if a >= 16 { tex_anisotropy = 16.0 }
  }
}
# Start the renderer in one call: the window, then every load step in order. A game that shows
# a loading screen calls r3d_open, draws its screen, and runs r3d_load_step itself between frames.
function r3d_init(w: int, h: int, title: string) -> bool {
  if not r3d_open(w, h, title) { return false }
  for i in 0 .. r3d_load_count() { if not r3d_load_step(i) { return false } }
  return true
}

# the window and the graphics backend; nothing is baked yet, but a frame can be presented
function r3d_open(w: int, h: int, title: string) -> bool {
  r3d_env_flags()
  gpu_select()
  if not gpu_open(w, h, title) { print("r3d: no OpenGL context");  return false }
  if r3d_env_has("R3D_NOVSYNC") { gpu_vsync(0) }
  var renderer: string = gpu_renderer_name()
  print(`r3d: {gl_w}x{gl_h} on {renderer}`)
  prof_init()
  cam_init(float(gl_w) / float(gl_h))
  return true
}

# The load, as steps a loading screen can show between: 0 the sky and its image-based light,
# 1 - 4 the terrain (the height field and normals, its sun shadow, its materials, its patches and
# programs), 5 the shadow maps and the screen targets, 6 the scattered cover and the actors, 7 the
# grass and the sky pass. The order is r3d_init's.
function r3d_load_count() -> int { return 4 + TERRAIN_INIT_STEPS }
function r3d_load_step(i: int) -> bool {
  let t = i - 1
  if i == 0 {
    var sky = r3d_assets + "/hdri/kloofendal_48d_partly_cloudy_puresky_4k.hdr"
    if r3d_sky_path != null { sky = r3d_sky_path }
    if not sky_load(sky) { return false }
    daylight_init()
  } else if t >= 0 and t < TERRAIN_INIT_STEPS {
    if r3d_plate { return true }
    if t == 0 {
      if r3d_dem_path != null { terrain_use_dem(r3d_dem_path, r3d_dem_min, r3d_dem_max, r3d_dem_base, r3d_dem_ox, r3d_dem_oz) }
      if r3d_ortho_path != null { terrain_use_ortho(r3d_ortho_path) }
    }
    terrain_init_step(t)
  } else if i == 1 + TERRAIN_INIT_STEPS {
    shadow_init()
    post_init(gl_w, gl_h)
  } else if i == 2 + TERRAIN_INIT_STEPS {
    scatter_init()
    actor_init()
  } else if i == 3 + TERRAIN_INIT_STEPS {
    if not r3d_plate { grass_init() }
    r3d_sky_prog = r3d_program("fullscreen.vert", "sky.frag", "")
    # The base is NOON's air, and it was tuned when nothing desaturated with distance - so it
    # was doing its whole job through colour and could not be raised without the valley going
    # blue. With the desaturation term carrying the depth, the air can be as thick as real air
    # at 2900 m and the far ridge recedes instead of tinting.
    r3d_fog_density = 0.00024
    r3d_fog_falloff = 0.002
    r3d_ready = true
    gpu_check("r3d init")
  }
  return true
}

function r3d_draw_sky() -> void {
  gpu_depth_func(GL_LEQUAL)
  gpu_depth_write(false)
  gpu_cull(false)
  let p = r3d_sky_prog
  gpu_use_program(p)
  r3d_bind_2d(p, "u_sky", 0, sky_tex)
  sky_bind_rot(p)
  sky_bind_lighting(p)
  u_mat4(gpu_uniform(p, "u_inv_vp"), cam_inv_vp)
  u_f(gpu_uniform(p, "u_sky_gain"), 0.95)
  u_f(gpu_uniform(p, "u_sky_relight"), r3d_sky_relight)
  u_f(gpu_uniform(p, "u_sky_sat"), 1.35)
  u_f(gpu_uniform(p, "u_time"), r3d_time)
  mesh_draw(sky_fullscreen)
  gpu_depth_write(true)
  gpu_depth_func(GL_LESS)
}

# The end of the game's frame, whichever backend draws it: a screenshot first if one is wanted,
# then the present. A game calls these rather than Gl.swap / Gl.screenshot.
function r3d_screenshot(path: string) -> bool { return gpu_screenshot(path) }
function r3d_present() -> void { gpu_present() }

# the drawable changed size: the camera's aspect and every screen-sized target follow
function r3d_resize() -> void {
  cam_aspect = float(gl_w) / float(gl_h)
  cam_update()
  post_free()
  post_init(gl_w, gl_h)
  if water_refl != null { target_free(water_refl);  water_refl = null }
  print(`r3d: resized to {gl_w}x{gl_h}`)
}
var r3d_cam_log: int = -1
function r3d_frame(time: float) -> void {
  gpu_glcheck_after("the time between frames")
  outline_frame()
  if not r3d_ready { return }
  if gpu_resize_check() { r3d_resize() }
  # R3D_RESIZE_AT=<frame>: rebuild every screen-sized buffer mid-run, as a window resize
  # or a fullscreen change does. Headless has no window to resize, and this path is where
  # a stale attachment or a texture freed twice shows up.
  r3d_test_frame += 1
  if r3d_test_resize == 0 and r3d_env_has("R3D_RESIZE_AT") { r3d_test_resize = Text.to_int(r3d_env("R3D_RESIZE_AT")) }
  # R3D_RESIZE_AT=<n>: from frame n on, rebuild every screen-sized buffer every few
  # frames at a different size, as dragging a window edge or entering fullscreen does.
  if r3d_test_resize > 0 and r3d_test_frame >= r3d_test_resize and r3d_test_frame % 4 == 0 {
    let step = (r3d_test_frame / 4) % 4
    var w = 1920;  var h = 1080
    if step == 1 { w = 1440;  h = 810 }
    if step == 2 { w = 2560;  h = 1440 }
    if step == 3 { w = 1281;  h = 721 }
    gl_w = w;  gl_h = h
    r3d_resize()
  }
  r3d_time = time
  gsl_frame_start()
  # the frame's counters close here, before any of its own work: the window each of them
  # covers is exactly one frame, from this point to the same point next time
  prof_gen_frame()
  prof_mark_start()
  cam_begin_frame(post_frame, gl_w, gl_h)
  # R3D_CAM_LOG=1: the camera each frame, in millimetres and thousandths of a radian - to tell a
  # camera that moves while the hiker stands still from a picture that shakes on its own
  if r3d_cam_log < 0 { r3d_cam_log = 0;  if r3d_env_has("R3D_CAM_LOG") { r3d_cam_log = 1 } }
  if r3d_cam_log == 1 {
    print(`cam {r3d_test_frame} pos {int(cam_pos[0] * 1000.0)} {int(cam_pos[1] * 1000.0)} {int(cam_pos[2] * 1000.0)} yaw {int(cam_yaw * 1000.0)} pitch {int(cam_pitch * 1000.0)} jitter {int(gsl_jitter_x * 1000000.0)} {int(gsl_jitter_y * 1000000.0)} render {post_w}x{post_h} reset {gsl_reset} evalok {gsl_eval_ok} fresh {gsl_fresh}`)
  }
  # the height-field shadow rebakes as the light moves in steps (daylight), or with the sky yaw when there is no clock
  if not r3d_plate and ((not day_on and ter_shadow_yaw != sky_yaw) or ter_shadow_gen != day_gen) {
    ter_shadow_gen = day_gen
    let t_bk = gl_now_us()
    terrain_bake_shadow()
    prof_bake_add(gl_now_us() - t_bk)
  }
  scatter_begin_frame()
  prof_cpu_mark("shadow rebake")
  stream_update_all()
  prof_cpu_mark("streaming")
  if not r3d_no_shadow { prof_begin("shadow");  shadow_pass();  prof_end() }
  prof_cpu_mark("shadow pass")
  if water_on and not r3d_no_refl and water_reflect_visible() { prof_begin("water reflection");  water_reflection_pass();  prof_end() }
  prof_cpu_mark("reflection")
  post_begin_scene()
  # the near tree foliage lays its depth down before anything is shaded, so the terrain
  # under the stands and the cards behind the front ones are rejected before lighting.
  # It has to come straight after post_begin_scene: terrain_sun_prepare binds its own
  # target, and depth drawn after it lands in the sun buffer, not the scene's.
  if not r3d_prepass_off() {
    prof_begin("foliage prepass")
    gpu_color_write(false)
    scatter_draw_depth()
    gpu_color_write(true)
    prof_end()
    sc_prepass = true
  }
  prof_cpu_mark("foliage prepass")
  if not r3d_plate {
    prof_begin("terrain sun")
    terrain_sun_prepare()
    prof_end()
    prof_begin("terrain")
    terrain_draw()
    prof_end()
  }
  prof_cpu_mark("terrain")
  prof_begin("scene (vegetation)")
  r3d_scene_draw()
  prof_end()
  sc_prepass = false
  prof_cpu_mark("vegetation")
  prof_begin("grass")
  grass_draw()
  prof_end()
  prof_cpu_mark("grass")
  prof_begin("sky")
  r3d_draw_sky()
  prof_end()
  prof_begin("resolve MSAA")
  post_resolve()
  prof_end()
  # transparent water over the resolved frame: it tests against the frame's own
  # depth and reads a copy of it for the depth tint and soft shores
  if water_on {
    prof_begin("water surface")
    post_capture_scene()
    target_bind(post_hdr)
    gpu_depth_test(true)
    gpu_depth_func(GL_LESS)
    water_draw(post_depth_copy.depth)
    prof_end()
  }
  post_color = post_hdr.color;  post_color_w = post_w;  post_color_h = post_h
  # DLSS super resolution: the lit frame up to the display's size, before anything reads it
  if gsl_dlss_live() { prof_begin("DLSS");  post_color = gsl_dlss_eval();  prof_end() }
  # Before bloom and before the tonemap: a shaft of light is a bright thing in the air and
  # should bloom like one.
  prof_begin("volumetric");  post_volumetric_pass();  prof_end()
  prof_begin("dof");  post_dof_pass();  prof_end()
  if not post_no_gi { prof_begin("SSAO/GI");  post_ssao_pass();  prof_end() }
  if r3d_debug_max { tex_max(post_hdr.color, post_hdr.w, post_hdr.h, "hdr") }
  prof_begin("bloom")
  post_bloom_pass()
  prof_end()
  prof_begin("tonemap+exposure")
  post_tonemap(post_color)
  prof_end()
  prof_cpu_mark("post")
  prof_begin("prev-colour copy")
  post_capture_prev()
  prof_end()
  prof_collect()
  gpu_check("frame")
}