shaders/ice_plasma.html

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<title>Сквозь лёд</title>
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html,body{margin:0;width:100%;height:100%;overflow:hidden;background:#03111d}
canvas{display:block;width:100%;height:100%;touch-action:none}
#info{position:fixed;bottom:20px;left:24px;color:#d8f4ff;font:13px/1.6 system-ui,sans-serif;text-shadow:0 1px 5px #001;pointer-events:none}
#info strong{font-weight:500} #info span{opacity:.75}
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<body>
<canvas id="view" aria-label="Плазма под прозрачным льдом. Двигайте указатель для параллакса."></canvas>
<div id="info" role="status"><strong>Сквозь лёд</strong><br><span id="help">Двигайте мышь · скорость − / =</span></div>
<script>
'use strict';
const sceneSource = "// Pass 1: eight plasma sheets, one atlas tile each. Alpha stores linear depth.\n// Density field lit as a height surface: billowing volumes with a real terminator.\nprecision highp float;\nuniform vec2 u_res; // size of one tile\nuniform float u_time;\n\nfloat hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }\nfloat noise(vec2 p) {\n  vec2 i = floor(p), f = fract(p);\n  f = f*f*(3.0-2.0*f);\n  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),\n             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);\n}\nfloat fbm(vec2 p) {\n  float sum = 0.0, amp = 0.5;\n  for (int i = 0; i < 4; i++) {\n    sum += amp * noise(p);\n    p = mat2(1.62, 1.17, -1.17, 1.62) * p;\n    amp *= 0.5;\n  }\n  return sum;\n}\nfloat fbm2(vec2 p) {\n  return 0.5 * noise(p) + 0.25 * noise(mat2(1.62, 1.17, -1.17, 1.62) * p);\n}\nconst float EXTENT = 3.8; // half-width of a sheet in world units; must match the ice pass\n\nvoid main() {\n  vec2 tile = floor(gl_FragCoord.xy / u_res);\n  float layer = tile.x + tile.y * 4.0;\n  vec2 uv = fract(gl_FragCoord.xy / u_res);\n  vec2 p = (uv - 0.5) * 2.0 * vec2(EXTENT * u_res.x / u_res.y, EXTENT);\n  p *= 0.85 + 0.10 * layer; // far sheets carry finer detail, which reads as distance\n  float angle = hash(vec2(layer, 3.1)) * 6.2831853;\n  p = mat2(cos(angle), sin(angle), -sin(angle), cos(angle)) * p;\n\n  // Periodic time: every field returns exactly after 30 seconds.\n  float phase = u_time * 6.2831853 / 30.0;\n  vec2 o = vec2(cos(phase), sin(phase));\n  vec2 seed = vec2(layer * 17.3, layer * 9.1);\n\n  // Two nested warp stages, the marbled-plasma motion.\n  vec2 q = vec2(fbm(p * 0.50 + seed + o * 0.55),\n                fbm(p * 0.50 + seed + 23.1 - o * 0.55));\n  vec2 r = vec2(fbm(p * 0.85 + 2.0 * q + seed + vec2(o.y, -o.x) * 0.40),\n                fbm(p * 0.85 + 2.0 * q + seed + 31.7 - vec2(o.y, -o.x) * 0.40));\n  vec2 w = p * 1.10 + 2.6 * r + seed;   // warped coords of the density field\n\n  // The silhouette is shared by all sheets (slid a little per depth), so the gaps\n  // stay open right through the stack instead of filling in with overlap.\n  float mass = smoothstep(0.520, 0.548, fbm((p + o * 0.30 + vec2(0.10, -0.07) * layer) * 0.62 + r * 1.1 + 13.7));\n\n  // Light the density as a height surface: $cheap 2-octave gradient, strong terminator.\n  float h = 0.05;\n  vec2 slope = vec2(fbm2(w + vec2(h, 0.0)) - fbm2(w - vec2(h, 0.0)),\n                    fbm2(w + vec2(0.0, h)) - fbm2(w - vec2(0.0, h))) * (10.0 / (2.0 * h));\n  vec3 nrm = normalize(vec3(-slope, 1.0));\n  float lit = clamp(dot(nrm, normalize(vec3(-0.38, 0.52, 0.76))), 0.0, 1.0);\n\n  // Folded planes across the volume, feathered so they never read as a grid.\n  vec2 g = (p + r * 2.0) * 1.4;\n  vec2 cell = floor(g), f = fract(g);\n  float feather = smoothstep(0.0, 0.10, min(min(f.x, 1.0 - f.x), min(f.y, 1.0 - f.y)));\n  float facet = mix(1.0, mix(0.70, 1.25, hash(cell + seed + step(1.0, f.x + f.y) * 37.0)), feather);\n\n  float shade = 0.05 + 1.10 * lit * lit;                // lit tops, near-black undersides\n  float e = mass * facet * shade * 0.085\n          + mass * (1.0 - mass) * 4.0 * 0.040           // thin torn silhouette\n          + mass * pow(lit, 14.0) * 0.110;              // glint where a fold faces the light\n  vec3 col = e * mix(vec3(0.02, 0.42, 0.60), vec3(0.08, 0.64, 0.88), facet * 0.5);\n  // Faint dye in the open gaps so darkness reads as depth, not as a hole.\n  col += smoothstep(0.40, 0.85, fbm(p * 0.30 + seed * 0.4 + o * 0.3)) * vec3(0.0003, 0.0011, 0.0015);\n\n  gl_FragColor = vec4(col, (0.42 + layer * 0.26) / 2.6);\n}\n";
const iceSource = "// Pass 2: clean ice. Refraction, chromatic shear, absorption by true path length.\n// Nothing is added to empty space, so the gaps between sheets stay black.\nprecision highp float;\nuniform vec2 u_res;\nuniform float u_time;\nuniform vec2 u_mouse; // normalized, bottom-left origin\nuniform sampler2D u_scene;\nuniform vec2 u_tile_res;\n\nconst float EXTENT = 3.8;                 // must match the plasma pass\nconst float FRONT  = -2.0;                // ice surface, camera at the origin looking down -z\nconst vec3  SIGMA  = vec3(0.66, 0.26, 0.11); // absorption per unit: red dies first, so depth turns blue\nconst float IOR    = 1.31;\n\nfloat hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }\nfloat noise(vec2 p) {\n  vec2 i = floor(p), f = fract(p);\n  f = f*f*(3.0-2.0*f);\n  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),\n             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);\n}\nfloat fbm(vec2 p) {\n  float sum = 0.0, amp = 0.5;\n  for (int i = 0; i < 3; i++) { sum += amp * noise(p); p = mat2(1.62, 1.17, -1.17, 1.62) * p; amp *= 0.5; }\n  return sum;\n}\nfloat fbm2(vec2 p) {\n  return 0.5 * noise(p) + 0.25 * noise(mat2(1.62, 1.17, -1.17, 1.62) * p);\n}\nvec2 atlasUV(vec2 world, float layer) {\n  vec2 uv = world / (2.0 * EXTENT) + 0.5;\n  uv = clamp(uv, 0.5 / u_tile_res, 1.0 - 0.5 / u_tile_res); // keep bilinear taps inside the tile\n  return (vec2(mod(layer, 4.0), floor(layer / 4.0)) + uv) / vec2(4.0, 2.0);\n}\n// The slab's fracture lines: two families of long, slightly wandering cracks. Shared\n// by the height field and the sheen, so each crack is both a bright seam and a step.\nvec2 fracture(vec2 x) {\n  float d = fbm(x * 0.62 + 3.0) - 0.5;                 // zero set: long winding cracks\n  float e = fbm(x * 1.35 - 7.0) - 0.5;                 // a sparser second family\n  return vec2(d, e);\n}\n// Frozen surface: fine ridged grain over the plates the cracks have lifted apart.\n// Static in world space; only the plasma behind it moves.\nfloat height(vec2 x) {\n  vec2 fr = fracture(x);\n  return 0.090 * (1.0 - abs(2.0 * fbm2(x * 2.2 + 2.0) - 1.0))\n       + 0.055 * (1.0 - abs(2.0 * fbm2(x * 6.4 - 5.0) - 1.0))\n       + 0.014 * clamp(fr.x * 110.0, -1.0, 1.0)  // the slab sits at a different level\n       + 0.009 * clamp(fr.y * 110.0, -1.0, 1.0); // on each side of a crack\n}\nvoid main() {\n  vec2 screen = gl_FragCoord.xy / u_res;\n  vec2 p = (gl_FragCoord.xy - 0.5 * u_res) / u_res.y;\n  vec2 look = clamp(u_mouse - 0.5, -0.35, 0.35); // orbiting the slab centre\n  vec3 ray = normalize(vec3(p - look * 2.2, -1.6));\n\n  // Front surface along the view ray; two fixed-point steps settle on the swell.\n  float t = FRONT / ray.z;\n  for (int i = 0; i < 2; i++) t = (FRONT + height(ray.xy * t)) / ray.z;\n  vec3 hit = ray * t;\n\n  float e = 0.008;\n  vec2 slope = vec2(height(hit.xy + vec2(e, 0.0)) - height(hit.xy - vec2(e, 0.0)),\n                    height(hit.xy + vec2(0.0, e)) - height(hit.xy - vec2(0.0, e))) / (2.0 * e);\n  float bevel = smoothstep(0.14, 0.0, min(min(screen.x, 1.0 - screen.x), min(screen.y, 1.0 - screen.y)));\n  slope += bevel * (screen - 0.5) * 0.55; // the slab turns away at the frame edge\n  vec3 normal = normalize(vec3(-slope, 1.0));\n  float facing = max(dot(-ray, normal), 0.0);\n\n  // Refracted ray; red and blue bend a little differently, which is what makes ice ring.\n  vec3 inside = refract(ray, normal, 1.0 / IOR);\n  vec2 shearR = (refract(ray, normal, 1.0 / (IOR - 0.012)) - inside).xy;\n  vec2 shearB = (refract(ray, normal, 1.0 / (IOR + 0.019)) - inside).xy;\n  inside = normalize(inside);\n  inside.z = min(inside.z, -0.40); // bound grazing rays at the crack steps\n\n  // Recentre the parallax on the middle of the sheet stack: near and far sheets\n  // then slide past each other at different rates as the pointer moves.\n  vec2 par = look * 4.54;\n\n  vec3 acc = vec3(0.0);\n  float trans = 1.0;\n  for (int i = 0; i < 8; i++) {\n    float layer = float(i);\n    float depth = texture2D(u_scene, atlasUV(hit.xy + par, layer)).a * 2.6; // depth buffer from pass 1\n    float path = (hit.z - (FRONT - depth)) / -inside.z;                     // ice crossed to reach this sheet\n    vec2 at = (hit + inside * path).xy + par;\n    vec3 plasma;\n    plasma.r = texture2D(u_scene, atlasUV(at + shearR * path, layer)).r;\n    plasma.g = texture2D(u_scene, atlasUV(at, layer)).g;\n    plasma.b = texture2D(u_scene, atlasUV(at + shearB * path, layer)).b;\n    vec3 c = plasma * exp(-SIGMA * path);\n    // Near plumes are nearly opaque, so the sheets behind them show through the gaps\n    // instead of averaging into a wash. That is what makes the stack read as depth.\n    float alpha = clamp(max(max(c.r, c.g), c.b) * 1.8, 0.0, 0.80);\n    acc += trans * c;\n    trans *= 1.0 - alpha;\n  }\n\n  // Gentle shoulder: overlapping glow stays coloured instead of clipping to white.\n  vec3 col = vec3(1.0) - exp(-acc * 1.5);\n\n  // Glass: reflection and a rim only where the surface turns away. Empty space stays dark.\n  float fresnel = pow(1.0 - facing, 5.0);\n  vec3 sky = mix(vec3(0.004, 0.016, 0.030), vec3(0.075, 0.220, 0.320), normal.y * 0.5 + 0.5);\n  col += sky * (fresnel * 1.2 + bevel * 0.03);\n  // Steep faces of the crests catch a thin sheen: the edge of the frozen surface,\n  // painted only where the ice actually tilts, so the open water stays black.\n  // Only the crack walls are this steep, so this sheen outlines the seams alone\n  // instead of washing the whole grain.\n  float tilt = smoothstep(1.00, 2.60, length(slope));\n  col += vec3(0.022, 0.062, 0.078) * tilt;\n  vec2 fr = fracture(hit.xy);\n  float crack = (1.0 - smoothstep(0.0, 0.004, abs(fr.x)))\n              + (1.0 - smoothstep(0.0, 0.004, abs(fr.y)));\n  col += vec3(0.020, 0.055, 0.068) * crack * smoothstep(0.58, 0.80, fbm2(hit.xy * 0.30 + 21.0));\n\n  gl_FragColor = vec4(pow(clamp(col, 0.0, 1.0), vec3(0.4545)), 1.0);\n}\n";
const vertexSource = 'attribute vec2 p; void main(){gl_Position=vec4(p,0.0,1.0);}';
const canvas = document.getElementById('view'), help = document.getElementById('help');
const gl = canvas.getContext('webgl', {antialias:false, alpha:false, preserveDrawingBuffer:true});
function fail(message) { help.textContent = message; throw new Error(message); }
if (!gl) fail('WebGL недоступен в этом браузере.');
function program(source) {
  function shader(type, code) {
    const s = gl.createShader(type);
    gl.shaderSource(s, code); gl.compileShader(s);
    if (!gl.getShaderParameter(s, gl.COMPILE_STATUS)) fail('Ошибка шейдера: ' + gl.getShaderInfoLog(s));
    return s;
  }
  const p = gl.createProgram(), vs = shader(gl.VERTEX_SHADER, vertexSource), fs = shader(gl.FRAGMENT_SHADER, source);
  gl.attachShader(p, vs); gl.attachShader(p, fs); gl.linkProgram(p);
  gl.deleteShader(vs); gl.deleteShader(fs);
  if (!gl.getProgramParameter(p, gl.LINK_STATUS)) fail('Ошибка программы: ' + gl.getProgramInfoLog(p));
  return p;
}
const scene = program(sceneSource), ice = program(iceSource);
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,-1,1,-1,-1,1,1,1]), gl.STATIC_DRAW);
let texture, framebuffer, tileWidth, tileHeight;
function resize() {
  const max = gl.getParameter(gl.MAX_TEXTURE_SIZE);
  const dpr = Math.min(devicePixelRatio || 1, 1.25, max / (innerWidth * 3), max / (innerHeight * 1.5));
  canvas.width = Math.max(4, Math.floor(innerWidth * dpr / 4) * 4);
  canvas.height = Math.max(4, Math.floor(innerHeight * dpr / 4) * 4);
  tileWidth = canvas.width * 3 / 4; tileHeight = canvas.height * 3 / 4;
  if (texture) gl.deleteTexture(texture);
  if (framebuffer) gl.deleteFramebuffer(framebuffer);
  texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, texture);
  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, tileWidth * 4, tileHeight * 2, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
  framebuffer = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
  if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) !== gl.FRAMEBUFFER_COMPLETE) fail('Не удалось создать текстуру сцены.');
  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
}
addEventListener('resize', resize); resize();
const shot = location.hash.startsWith('#shot');
const shotParams = new URLSearchParams(location.hash.slice(1));
let mouseX = Number(shotParams.get('mx') ?? 0.5), mouseY = Number(shotParams.get('my') ?? 0.5);
let speed = 1, time = Number(shotParams.get('t') ?? 0), previous;
addEventListener('pointermove', e => { mouseX = e.clientX / innerWidth; mouseY = 1 - e.clientY / innerHeight; });
addEventListener('keydown', e => {
  if (e.key === '-' || e.key === '_') speed = Math.max(0.125, speed / 2);
  else if (e.key === '=' || e.key === '+') speed = Math.min(4, speed * 2);
  else return;
  help.textContent = 'Двигайте мышь · скорость ' + speed + '×  (− / =)';
});
function draw(p, width, height) {
  gl.useProgram(p);
  const position = gl.getAttribLocation(p, 'p');
  gl.bindBuffer(gl.ARRAY_BUFFER, buffer); gl.enableVertexAttribArray(position);
  gl.vertexAttribPointer(position, 2, gl.FLOAT, false, 0, 0);
  gl.uniform2f(gl.getUniformLocation(p, 'u_res'), width, height);
  gl.uniform1f(gl.getUniformLocation(p, 'u_time'), time);
  gl.uniform2f(gl.getUniformLocation(p, 'u_mouse'), mouseX, mouseY);
  gl.uniform2f(gl.getUniformLocation(p, 'u_tile_res'), tileWidth, tileHeight);
  gl.uniform1i(gl.getUniformLocation(p, 'u_scene'), 0);
  gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
}
function frame(now) {
  if (previous !== undefined) time += (now - previous) * 0.001 * speed;
  previous = now;
  gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
  gl.viewport(0, 0, tileWidth * 4, tileHeight * 2);
  draw(scene, tileWidth, tileHeight);
  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
  gl.viewport(0, 0, canvas.width, canvas.height);
  gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, texture);
  draw(ice, canvas.width, canvas.height);
  if (shot) {
    // Headless Firefox does not composite WebGL; expose the actual rendered pixels.
    const pixels = new Uint8Array(canvas.width * canvas.height * 4);
    gl.readPixels(0, 0, canvas.width, canvas.height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
    const output = document.createElement('canvas');
    output.width = canvas.width; output.height = canvas.height;
    const ctx = output.getContext('2d'), image = ctx.createImageData(output.width, output.height);
    for (let y = 0; y < output.height; y++)
      image.data.set(pixels.subarray((output.height - y - 1) * output.width * 4, (output.height - y) * output.width * 4), y * output.width * 4);
    ctx.putImageData(image, 0, 0); canvas.replaceWith(output);
  } else requestAnimationFrame(frame);
}
if (shot) frame(0); else requestAnimationFrame(frame);
</script>
</body>
</html>