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ludic/packages/ludic.render3d/shadow.ludic
Orkuncakilkaya 54eeef5f8d feat(render3d): gpu.ludic - the seam for a second graphics API, and what the GPU can do 
Render state (depth, blending, culling, colour writes, alpha-to-coverage, depth bias,
scissor) and uniforms go through gpu_* / u_* and nowhere else; OpenGL state is cached and
only changes reach the driver. Frames are bit-identical to before at the fixed viewpoints.
R3D_GFX=gl|vk or gpu_request chooses a backend, falling back to OpenGL with a reason.

gpu_caps_probe() asks Vulkan, on Windows, for the 1.3 floor, ray tracing, mesh shaders, the
NVIDIA RTX generation, Reflex and HDR colour spaces, for a game's settings to grey out what
a machine cannot use; R3D_CAPS pretends to be a given card for tests.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-15 09:52:12 +03:00

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# ============================================================================
# shadow.ludic — cascaded shadow maps for the sun: four 2048^2 depth layers,
# each an orthographic light frustum fitted to the bounding sphere of a slice
# of the camera frustum and snapped to its own texel grid (no swimming).
# ============================================================================
const SHADOW_RES: int = 2048
const SHADOW_CASCADES: int = 5
var sh_tex: int = 0
var sh_fbo: int = 0
var sh_vp: words = null # 4 x 16 float bits
var sh_split: words = null # view-space far distance of each cascade
var sh_range: words = null # 4 light-frustum depth extents (metres)
var sh_texel: words = null # 4 shadow texel sizes (metres)
var sh_tmp_proj: words = null
var sh_tmp_vp: words = null
var sh_tmp_inv: words = null
var sh_tmp_view: words = null
var sh_corner: words = null
var sh_cascade: int = 0 # the cascade being rendered (for casters that skip far ones)
function shadow_init() -> void {
sh_tex = gl_texture()
gl_bind_texture(GL_TEXTURE_2D_ARRAY, sh_tex)
gl_tex_image3d(GL_TEXTURE_2D_ARRAY, 0, GL_DEPTH_COMPONENT32F, SHADOW_RES, SHADOW_RES, SHADOW_CASCADES, 0, GL_DEPTH_COMPONENT, GL_FLOAT, null)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL)
let border = gl_floats(4)
gl_put(border, 0, 1.0); gl_put(border, 1, 1.0); gl_put(border, 2, 1.0); gl_put(border, 3, 1.0)
gl_tex_parameterfv(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_BORDER_COLOR, border)
free(border)
sh_fbo = gl_framebuffer()
gl_bind_framebuffer(GL_FRAMEBUFFER, sh_fbo)
gl_draw_buffer(GL_NONE)
gl_read_buffer(GL_NONE)
gl_bind_framebuffer(GL_FRAMEBUFFER, 0)
sh_vp = words(16 * SHADOW_CASCADES)
sh_split = words(SHADOW_CASCADES)
sh_range = words(SHADOW_CASCADES)
sh_texel = words(SHADOW_CASCADES)
# the fourth slice keeps a tree-sized texel out to a kilometre; only the massif uses the last
sh_split[0] = fi(16); sh_split[1] = fi(60); sh_split[2] = fi(250); sh_split[3] = fi(1100); sh_split[4] = fi(6000)
sh_tmp_proj = m4_new(); sh_tmp_vp = m4_new(); sh_tmp_inv = m4_new(); sh_tmp_view = m4_new()
sh_corner = words(3)
}
# light view-projection for the camera-frustum slice [near, far]
function shadow_fit(c: int, near: int, far: int) -> void {
# Fit the slice in VIEW space, not world space. The bounding sphere of a frustum
# slice depends only on near/far/fov/aspect — never on where the camera is pointing —
# so computing it here makes the radius a constant per cascade. Doing it in world
# space (as this did) let the radius wobble as the camera turned, which changed the
# texel size, which moved the grid the projection is snapped to, so the whole shadow
# map resampled every frame: that is the crawl and flicker seen while moving.
m4_perspective(sh_tmp_proj, cam_fov, cam_aspect, near, far)
m4_inverse(sh_tmp_inv, sh_tmp_proj) # NDC -> view space
let cview = v3_new(F_ZERO, F_ZERO, F_ZERO)
let corners = words(24)
for i in 0 .. 8 {
var x = f_neg1(); var y = f_neg1(); var z = f_neg1()
if (i & 1) != 0 { x = F_ONE }
if (i & 2) != 0 { y = F_ONE }
if (i & 4) != 0 { z = F_ONE }
let w = m4_xform_point(sh_corner, sh_tmp_inv, x, y, z)
let iw = f_div(F_ONE, w)
corners[i * 3] = f_mul(sh_corner[0], iw); corners[i * 3 + 1] = f_mul(sh_corner[1], iw); corners[i * 3 + 2] = f_mul(sh_corner[2], iw)
cview[0] = f_add(cview[0], corners[i * 3]); cview[1] = f_add(cview[1], corners[i * 3 + 1]); cview[2] = f_add(cview[2], corners[i * 3 + 2])
}
v3_scale(cview, cview, fr(1, 8))
var radius = F_ZERO
for i in 0 .. 8 {
v3_set(sh_corner, corners[i * 3], corners[i * 3 + 1], corners[i * 3 + 2])
let d = v3_dist(sh_corner, cview)
if f_gt(d, radius) { radius = d }
}
radius = f_mul(radius, fl(1.05))
# the slice centre back into world space
m4_inverse(sh_tmp_vp, cam_view)
let center = words(3)
m4_xform_point(center, sh_tmp_vp, cview[0], cview[1], cview[2])
free(cview)
# light view: from far along the sun direction, looking at the centre
let eye = words(3)
# casters up to ~900 m toward the sun (a mountain across the valley), and the
# slice itself behind the centre: a tight depth range keeps the bias small
let back = f_add(radius, fi(900))
v3_madd(eye, center, sun_dir, back)
let up = v3_new(F_ZERO, F_ONE, F_ZERO)
m4_look_at(sh_tmp_view, eye, center, up)
# snap the ortho window to the shadow texel grid
let texel = f_div(f_mul(radius, F_TWO), fi(SHADOW_RES))
m4_xform_point(sh_corner, sh_tmp_view, center[0], center[1], center[2])
let ox = f_sub(f_mul(f_floor(f_div(sh_corner[0], texel)), texel), sh_corner[0])
let oy = f_sub(f_mul(f_floor(f_div(sh_corner[1], texel)), texel), sh_corner[1])
let nr = f_neg(radius)
let zfar = f_add(f_add(back, radius), fi(100))
m4_ortho(sh_tmp_proj, f_add(nr, ox), f_add(radius, ox), f_add(nr, oy), f_add(radius, oy), F_ONE, zfar)
sh_range[c] = f_sub(zfar, F_ONE)
sh_texel[c] = texel
let out = words(16)
m4_mul(out, sh_tmp_proj, sh_tmp_view)
for i in 0 .. 16 { sh_vp[c * 16 + i] = out[i] }
free(out); free(eye); free(up); free(center); free(corners)
}
function shadow_cascade_vp(c: int) -> words { return mem_off(sh_vp, c * 64) }
# render every cascade; `draw` happens through terrain_draw_shadow + the scene's casters
function shadow_pass() -> void {
var near = cam_near
gl_bind_framebuffer(GL_FRAMEBUFFER, sh_fbo)
gl_viewport(0, 0, SHADOW_RES, SHADOW_RES)
gpu_depth_test(true)
gpu_depth_func(GL_LESS)
gpu_depth_bias(2.0, 4.0)
gpu_cull(false)
for c in 0 .. SHADOW_CASCADES {
sh_cascade = c
shadow_fit(c, near, sh_split[c])
near = sh_split[c]
gl_framebuffer_texture_layer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, sh_tex, 0, c)
if r3d_debug and c == 0 { let st = gl_check_framebuffer_status(GL_FRAMEBUFFER); print(`shadow fbo status {st}`) }
gl_clear(GL_DEPTH_BUFFER_BIT)
let vp = shadow_cascade_vp(c)
# shadows off (a video setting): the cascades stay cleared, so everything reads lit
if sh_enabled {
if not sh_skip_terrain { terrain_draw_shadow(vp) }
scene_draw_casters(vp)
}
}
gpu_depth_bias(0.0, 0.0)
gl_bind_framebuffer(GL_FRAMEBUFFER, 0)
if r3d_debug_shadow { shadow_dump() }
if r3d_debug_shadow and not sh_printed2 {
sh_printed2 = true
let q = words(3)
if sh_probe_x != 0 {
let vp = shadow_cascade_vp(2)
m4_xform_point(q, vp, sh_probe_x, sh_probe_y, sh_probe_z)
print(`probe base ndc {f_fx(q[0])} {f_fx(q[1])} {f_fx(q[2])}`)
m4_xform_point(q, vp, sh_probe_x, f_add(sh_probe_y, fi(15)), sh_probe_z)
print(`probe top ndc {f_fx(q[0])} {f_fx(q[1])} {f_fx(q[2])} -> map texel {f_to_int(f_mul(f_add(f_mul(q[0], F_HALF), F_HALF), fi(SHADOW_RES)))} {f_to_int(f_mul(f_add(f_mul(q[1], F_HALF), F_HALF), fi(SHADOW_RES)))}`)
# where the top's shadow lands on the ground: walk down the sun ray
let gx = f_sub(f_add(sh_probe_x, F_ZERO), f_mul(sun_dir[0], f_div(fi(15), sun_dir[1])))
let gz = f_sub(sh_probe_z, f_mul(sun_dir[2], f_div(fi(15), sun_dir[1])))
m4_xform_point(q, vp, gx, terrain_height(gx, gz), gz)
print(`shadow-of-top ground ndc {f_fx(q[0])} {f_fx(q[1])} {f_fx(q[2])} at {f_fx(gx)} {f_fx(gz)}`)
}
for c in 0 .. SHADOW_CASCADES {
let vp = shadow_cascade_vp(c)
# a point 5 m ahead of the camera on the ground
let px = f_add(cam_pos[0], f_mul(cam_fwd[0], fi(5))); let pz = f_add(cam_pos[2], f_mul(cam_fwd[2], fi(5)))
let w = m4_xform_point(q, vp, px, terrain_height(px, pz), pz)
print(`cascade {c}: ndc {f_fx(q[0])} {f_fx(q[1])} {f_fx(q[2])} w {f_fx(w)} m0 {f_fx(vp[0])} m5 {f_fx(vp[5])} m14 {f_fx(vp[14])}`)
}
free(q)
}
}
var sh_printed2: bool = false
var sh_printed3: bool = false
var sh_enabled: bool = true
var sh_force: int = -1 # R3D_FORCE=<c> pins every pixel to cascade c (debug)
var sh_skip_terrain: bool = false
var sh_probe_x: int = 0
var sh_probe_y: int = 0
var sh_probe_z: int = 0
# Debug: cascade depths as grey PPMs (build/dbg_shadow_<c>.ppm)
function shadow_dump() -> void {
let n = SHADOW_RES * SHADOW_RES
let buf = words(n * SHADOW_CASCADES)
gl_bind_texture(GL_TEXTURE_2D_ARRAY, sh_tex)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_MODE, GL_NONE)
gl_get_tex_image(GL_TEXTURE_2D_ARRAY, 0, GL_DEPTH_COMPONENT, GL_FLOAT, buf)
gl_tex_parameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE)
if sh_probe_x != 0 {
let vp = shadow_cascade_vp(2)
let q = words(3)
m4_xform_point(q, vp, sh_probe_x, f_add(sh_probe_y, fi(12)), sh_probe_z)
let tx = f_to_int(f_mul(f_add(f_mul(q[0], F_HALF), F_HALF), fi(SHADOW_RES)))
let ty = f_to_int(f_mul(f_add(f_mul(q[1], F_HALF), F_HALF), fi(SHADOW_RES)))
let want = f_add(f_mul(q[2], F_HALF), F_HALF)
print(`probe (12 m up) texel {tx} {ty} card depth {f_fx(f_mul(want, fi(1000)))}/1000`)
for dy in 0 .. 5 {
let yy = ty - 40 + dy * 20
print(` row {yy}: {f_fx(f_mul(buf[2 * n + yy * SHADOW_RES + tx - 20], fi(1000)))} {f_fx(f_mul(buf[2 * n + yy * SHADOW_RES + tx], fi(1000)))} {f_fx(f_mul(buf[2 * n + yy * SHADOW_RES + tx + 20], fi(1000)))} /1000`)
}
free(q)
}
let sm = 512
let row = bytes(sm * 3)
for c in 0 .. SHADOW_CASCADES {
# stretch between the map's own min and max (ignoring the far plane)
var lo = F_ONE; var hi = F_ZERO
var i = 0
while i < n { let d = buf[c * n + i]; if f_ls(d, fl(0.999)) { if f_ls(d, lo) { lo = d }; if f_gt(d, hi) { hi = d } }; i += 97 }
print(`cascade {c} depth range {f_fx(lo)} .. {f_fx(hi)}`)
let f = file_open(`build/dbg_shadow_{c}.ppm`, "wb")
let hdr = `P6\n{sm} {sm}\n255\n`
file_write(f, hdr, len(hdr))
let st = SHADOW_RES / sm
for y in 0 .. sm {
for x in 0 .. sm {
let d = buf[c * n + (y * st) * SHADOW_RES + x * st]
let g = f_to_int(f_mul(f_clamp(f_div(f_sub(d, lo), f_max(f_sub(hi, lo), fl(0.0001))), F_ZERO, F_ONE), fi(255)))
row[x * 3] = g; row[x * 3 + 1] = g; row[x * 3 + 2] = g
}
file_write(f, row, sm * 3)
}
file_close(f)
}
free(buf); free(row)
}
var sh_printed: bool = false
# a uniform array's location: some drivers only answer to the "[0]" spelling
function sh_loc(prog: int, name: string) -> int {
var loc = gpu_uniform(prog, name + "[0]")
if loc < 0 { loc = gpu_uniform(prog, name) }
return loc
}
function shadow_bind(prog: int) -> void {
r3d_bind_tex(prog, "u_shadow", 15, GL_TEXTURE_2D_ARRAY, sh_tex)
# the height-field shadow (terrain.ludic); a stand-in texture keeps the unit valid before the bake
var ts = ter_shadow_tex
var ts_on = F_ONE
if ts == 0 { ts = ter_height_tex; ts_on = F_ZERO }
r3d_bind_2d(prog, "u_tershadow", 6, ts)
terrain_bind_height(prog)
u_f(gpu_uniform(prog, "u_ts_on"), ts_on)
u_f(gpu_uniform(prog, "u_ts_half"), fi(TERRAIN_HALF))
u_f2(gpu_uniform(prog, "u_ts_origin"), ter_ox, ter_oz)
var loc = gpu_uniform(prog, "u_cascade_vp[0]")
if loc < 0 { loc = gpu_uniform(prog, "u_cascade_vp") }
if r3d_debug_shadow and not sh_printed { sh_printed = true; print(`cascade vp loc {loc} / {gpu_uniform(prog, "u_cascade_vp")} split loc {gpu_uniform(prog, "u_cascade_split")} shadow loc {gpu_uniform(prog, "u_shadow")}`) }
u_mat4n(loc, SHADOW_CASCADES, sh_vp)
u_fv(sh_loc(prog, "u_cascade_split"), SHADOW_CASCADES, sh_split)
if r3d_debug_shadow and not sh_printed3 { sh_printed3 = true; print(`range {f_fx(sh_range[0])} {f_fx(sh_range[1])} {f_fx(sh_range[2])} {f_fx(sh_range[3])} texel*1000 {f_fx(f_mul(sh_texel[0], fi(1000)))} {f_fx(f_mul(sh_texel[1], fi(1000)))} {f_fx(f_mul(sh_texel[2], fi(1000)))} {f_fx(f_mul(sh_texel[3], fi(1000)))} locs {gpu_uniform(prog, "u_cascade_range")} {gpu_uniform(prog, "u_cascade_texel")}`) }
u_fv(sh_loc(prog, "u_cascade_range"), SHADOW_CASCADES, sh_range)
if Os.has_env("R3D_FORCE") { sh_force = Text.to_int(Os.env("R3D_FORCE")) }
u_i(gpu_uniform(prog, "u_force_cascade"), sh_force)
u_fv(sh_loc(prog, "u_cascade_texel"), SHADOW_CASCADES, sh_texel)
}
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