mapwright/module/lib/render-cave.mjs

/**
 * Organic cave renderer: smoothed contour loops -> SVG.
 *
 * The look: rocky floor inside flowing walls, thick rock walls with a cast
 * shadow + inner highlight, scattered floor debris, optional grid clipped to
 * floor. Pure + deterministic.
 */

import { Rng } from "./rng.mjs";

const THEMES = {
  cave: {
    outside: "#0f0d0b", floorBase: "#7d7164", floorSpeck: "#8d8173",
    floorEdge: "#5e5349", wall: "#1d1813", wallHi: "#5a5042",
    grid: "#3a342e", label: "#f3e9d4", speckLight: "#9a8e80"
  },
  crypt: {
    outside: "#0c0e12", floorBase: "#6a6f7c", floorSpeck: "#7a8090",
    floorEdge: "#50545f", wall: "#171a20", wallHi: "#566173",
    grid: "#33363d", label: "#eef3fb", speckLight: "#8990a0"
  },
  sewer: {
    outside: "#0c100e", floorBase: "#61705f", floorSpeck: "#6e7e69",
    floorEdge: "#4a564a", wall: "#161d18", wallHi: "#566355",
    grid: "#2f3733", label: "#e7f5ec", speckLight: "#7e8e78"
  }
};

const PX = (v, gs) => +(v * gs).toFixed(1);

export function renderCaveSVG(args) {
  const model = args.model;
  const gs = args.gridSize ?? 70;
  const theme = THEMES[args.theme] ?? THEMES.cave;
  const showGrid = args.showGrid !== false;
  const showLabels = args.showLabels !== false;
  const rng = new Rng(`${args.seed ?? "cave"}::caverender`);

  const W = model.cols * gs;
  const H = model.rows * gs;
  const out = [];

  const pathFor = (pts) => {
    let d = `M${PX(pts[0].x, gs)},${PX(pts[0].y, gs)}`;
    for (let i = 1; i < pts.length; i += 1) d += `L${PX(pts[i].x, gs)},${PX(pts[i].y, gs)}`;
    return d + "Z";
  };
  const floorPath = model.loops.map((lp) => pathFor(lp.smooth)).join(" ");

  out.push(`<svg xmlns="http://www.w3.org/2000/svg" width="${W}" height="${H}" viewBox="0 0 ${W} ${H}">`);

  out.push(`<defs>`);
  out.push(
    `<filter id="mw-rockshadow" x="-20%" y="-20%" width="140%" height="140%">` +
    `<feDropShadow dx="0" dy="0" stdDeviation="${(gs * 0.09).toFixed(1)}" flood-color="#000" flood-opacity="0.55"/></filter>`
  );
  out.push(`<clipPath id="mw-cavefloor" clip-rule="evenodd"><path d="${floorPath}" clip-rule="evenodd"/></clipPath>`);
  out.push(`</defs>`);

  // Rock surround.
  out.push(`<rect x="0" y="0" width="${W}" height="${H}" fill="${theme.outside}"/>`);
  out.push(rockTexture(W, H, theme, gs, rng));

  // Floor fill (evenodd handles pillars/holes).
  out.push(`<path d="${floorPath}" fill="${theme.floorBase}" fill-rule="evenodd"/>`);

  // Floor detail clipped to floor.
  out.push(`<g clip-path="url(#mw-cavefloor)">`);
  out.push(floorDebris(model, gs, theme, rng));
  if (showGrid) out.push(caveGrid(model, gs, theme.grid));
  // inner shading ring just inside the walls
  out.push(`<path d="${floorPath}" fill="none" fill-rule="evenodd" stroke="${theme.floorEdge}" stroke-width="${(gs * 0.34).toFixed(1)}" opacity="0.5"/>`);
  out.push(`</g>`);

  // Walls: cast shadow, body, inner highlight.
  const wallW = (gs * 0.26).toFixed(1);
  out.push(`<g filter="url(#mw-rockshadow)" fill="none" stroke-linejoin="round">`);
  out.push(`<path d="${floorPath}" fill-rule="evenodd" stroke="${theme.wall}" stroke-width="${wallW}"/>`);
  out.push(`</g>`);
  out.push(`<path d="${floorPath}" fill="none" fill-rule="evenodd" stroke="${theme.wallHi}" stroke-width="${(gs * 0.05).toFixed(1)}" opacity="0.5"/>`);

  // Feature labels.
  if (showLabels && model.features?.length) {
    out.push(`<g font-family="'Segoe UI', sans-serif" text-anchor="middle" fill="${theme.label}">`);
    for (const f of model.features) {
      const fs = Math.max(10, gs * 0.22);
      out.push(`<circle cx="${PX(f.x, gs)}" cy="${PX(f.y, gs)}" r="${(gs * 0.08).toFixed(1)}" fill="${theme.label}" opacity="0.5"/>`);
      out.push(`<text x="${PX(f.x, gs)}" y="${(PX(f.y, gs) - gs * 0.18).toFixed(1)}" font-size="${fs.toFixed(1)}" font-weight="600" opacity="0.85">${escapeXml(f.label)}</text>`);
    }
    out.push(`</g>`);
  }

  out.push(`</svg>`);
  return out.join("");
}

function rockTexture(W, H, theme, gs, rng) {
  // Sparse rock cracks/blotches outside, very subtle.
  const out = [`<g stroke="${theme.wallHi}" stroke-width="${(gs * 0.02).toFixed(1)}" opacity="0.12" fill="none">`];
  const n = Math.round((W * H) / (gs * gs) / 6);
  for (let i = 0; i < n; i += 1) {
    const x = rng.float() * W, y = rng.float() * H;
    const len = gs * (0.3 + rng.float() * 0.5);
    const ang = rng.float() * Math.PI;
    out.push(`<line x1="${x.toFixed(1)}" y1="${y.toFixed(1)}" x2="${(x + Math.cos(ang) * len).toFixed(1)}" y2="${(y + Math.sin(ang) * len).toFixed(1)}"/>`);
  }
  out.push(`</g>`);
  return out.join("");
}

function floorDebris(model, gs, theme, rng) {
  const out = [`<g>`];
  const n = Math.round(model.cols * model.rows * 0.6);
  for (let i = 0; i < n; i += 1) {
    const x = rng.float() * model.cols, y = rng.float() * model.rows;
    const r = gs * (0.02 + rng.float() * 0.06);
    const col = rng.float() < 0.5 ? theme.floorSpeck : theme.speckLight;
    out.push(`<circle cx="${PX(x, gs)}" cy="${PX(y, gs)}" r="${r.toFixed(1)}" fill="${col}" opacity="${(0.25 + rng.float() * 0.3).toFixed(2)}"/>`);
  }
  out.push(`</g>`);
  return out.join("");
}

function caveGrid(model, gs, color) {
  const out = [`<g stroke="${color}" stroke-width="${(gs * 0.012).toFixed(1)}" opacity="0.18">`];
  for (let x = 0; x <= model.cols; x += 1) out.push(`<line x1="${PX(x, gs)}" y1="0" x2="${PX(x, gs)}" y2="${PX(model.rows, gs)}"/>`);
  for (let y = 0; y <= model.rows; y += 1) out.push(`<line x1="0" y1="${PX(y, gs)}" x2="${PX(model.cols, gs)}" y2="${PX(y, gs)}"/>`);
  out.push(`</g>`);
  return out.join("");
}

function escapeXml(str) {
  return String(str).replace(/[<>&'"]/g, (c) => ({ "<": "&lt;", ">": "&gt;", "&": "&amp;", "'": "&apos;", '"': "&quot;" }[c]));
}