Fantasy-Map-Generator/src/scripts/generation/pack/repackGrid.ts

import * as d3 from "d3";

import {UINT16_MAX} from "config/constants";
import {DISTANCE_FIELD, MIN_LAND_HEIGHT} from "config/generation";
import {TIME} from "config/logging";
import {createTypedArray} from "utils/arrayUtils";
import {rn} from "utils/numberUtils";
import {calculateVoronoi} from "../graph";

const {LAND_COAST, WATER_COAST, DEEPER_WATER} = DISTANCE_FIELD;

// repack grid cells: discart deep water cells, add land cells along the coast
export function repackGrid(grid: IGrid) {
  TIME && console.time("repackGrid");
  const {cells: gridCells, points, features} = grid;
  const newCells: {p: TPoints; g: number[]; h: number[]} = {p: [], g: [], h: []}; // store new data
  const spacing2 = grid.spacing ** 2;

  for (const i of gridCells.i) {
    const height = gridCells.h[i];
    const type = gridCells.t[i];

    // exclude ocean points far from coast
    if (height < MIN_LAND_HEIGHT && type !== WATER_COAST && type !== DEEPER_WATER) continue;

    const feature = features[gridCells.f[i]];
    const isLake = feature && feature.type === "lake";

    // exclude non-coastal lake points
    if (type === DEEPER_WATER && (i % 4 === 0 || isLake)) continue;

    const [x, y] = points[i];
    addNewPoint(i, x, y, height);

    // add additional points for cells along coast
    if (type === LAND_COAST || type === WATER_COAST) {
      if (gridCells.b[i]) continue; // not for near-border cells
      gridCells.c[i].forEach(e => {
        if (i > e) return;
        if (gridCells.t[e] === type) {
          const dist2 = (y - points[e][1]) ** 2 + (x - points[e][0]) ** 2;
          if (dist2 < spacing2) return; // too close to each other
          const x1 = rn((x + points[e][0]) / 2, 1);
          const y1 = rn((y + points[e][1]) / 2, 1);
          addNewPoint(i, x1, y1, height);
        }
      });
    }
  }

  function addNewPoint(i: number, x: number, y: number, height: number) {
    newCells.p.push([x, y]);
    newCells.g.push(i);
    newCells.h.push(height);
  }

  const {cells, vertices} = calculateVoronoi(newCells.p, grid.boundary);

  function getCellArea(i: number) {
    const polygon = cells.v[i].map(v => vertices.p[v]);
    const area = Math.abs(d3.polygonArea(polygon));
    return Math.min(area, UINT16_MAX);
  }

  const pack = {
    vertices,
    cells: {
      ...cells,
      p: newCells.p,
      g: createTypedArray({maxValue: grid.points.length, from: newCells.g}),
      q: d3.quadtree(newCells.p.map(([x, y], i) => [x, y, i])),
      h: new Uint8Array(newCells.h),
      area: createTypedArray({maxValue: UINT16_MAX, from: cells.i}).map(getCellArea)
    }
  };

  TIME && console.timeEnd("repackGrid");
  return pack;
}