@deck.gl/layers/dist/esm/solid-polygon-layer/polygon.js

deck.gl core layers

import earcut from 'earcut';
import { modifyPolygonWindingDirection, WINDING } from '@math.gl/polygon';
const OUTER_POLYGON_WINDING = WINDING.CLOCKWISE;
const HOLE_POLYGON_WINDING = WINDING.COUNTER_CLOCKWISE;
const windingOptions = {
  isClosed: true
};

function validate(polygon) {
  polygon = polygon && polygon.positions || polygon;

  if (!Array.isArray(polygon) && !ArrayBuffer.isView(polygon)) {
    throw new Error('invalid polygon');
  }
}

export function getPositions(polygon) {
  return 'positions' in polygon ? polygon.positions : polygon;
}
export function getHoleIndices(polygon) {
  return 'holeIndices' in polygon ? polygon.holeIndices : null;
}

function isNested(polygon) {
  return Array.isArray(polygon[0]);
}

function isSimple(polygon) {
  return polygon.length >= 1 && polygon[0].length >= 2 && Number.isFinite(polygon[0][0]);
}

function isNestedRingClosed(simplePolygon) {
  const p0 = simplePolygon[0];
  const p1 = simplePolygon[simplePolygon.length - 1];
  return p0[0] === p1[0] && p0[1] === p1[1] && p0[2] === p1[2];
}

function isFlatRingClosed(positions, size, startIndex, endIndex) {
  for (let i = 0; i < size; i++) {
    if (positions[startIndex + i] !== positions[endIndex - size + i]) {
      return false;
    }
  }

  return true;
}

function copyNestedRing(target, targetStartIndex, simplePolygon, size, windingDirection) {
  let targetIndex = targetStartIndex;
  const len = simplePolygon.length;

  for (let i = 0; i < len; i++) {
    for (let j = 0; j < size; j++) {
      target[targetIndex++] = simplePolygon[i][j] || 0;
    }
  }

  if (!isNestedRingClosed(simplePolygon)) {
    for (let j = 0; j < size; j++) {
      target[targetIndex++] = simplePolygon[0][j] || 0;
    }
  }

  windingOptions.start = targetStartIndex;
  windingOptions.end = targetIndex;
  windingOptions.size = size;
  modifyPolygonWindingDirection(target, windingDirection, windingOptions);
  return targetIndex;
}

function copyFlatRing(target, targetStartIndex, positions, size, srcStartIndex = 0, srcEndIndex, windingDirection) {
  srcEndIndex = srcEndIndex || positions.length;
  const srcLength = srcEndIndex - srcStartIndex;

  if (srcLength <= 0) {
    return targetStartIndex;
  }

  let targetIndex = targetStartIndex;

  for (let i = 0; i < srcLength; i++) {
    target[targetIndex++] = positions[srcStartIndex + i];
  }

  if (!isFlatRingClosed(positions, size, srcStartIndex, srcEndIndex)) {
    for (let i = 0; i < size; i++) {
      target[targetIndex++] = positions[srcStartIndex + i];
    }
  }

  windingOptions.start = targetStartIndex;
  windingOptions.end = targetIndex;
  windingOptions.size = size;
  modifyPolygonWindingDirection(target, windingDirection, windingOptions);
  return targetIndex;
}

export function normalize(polygon, positionSize) {
  validate(polygon);
  const positions = [];
  const holeIndices = [];

  if ('positions' in polygon) {
    const {
      positions: srcPositions,
      holeIndices: srcHoleIndices
    } = polygon;

    if (srcHoleIndices) {
      let targetIndex = 0;

      for (let i = 0; i <= srcHoleIndices.length; i++) {
        targetIndex = copyFlatRing(positions, targetIndex, srcPositions, positionSize, srcHoleIndices[i - 1], srcHoleIndices[i], i === 0 ? OUTER_POLYGON_WINDING : HOLE_POLYGON_WINDING);
        holeIndices.push(targetIndex);
      }

      holeIndices.pop();
      return {
        positions,
        holeIndices
      };
    }

    polygon = srcPositions;
  }

  if (!isNested(polygon)) {
    copyFlatRing(positions, 0, polygon, positionSize, 0, positions.length, OUTER_POLYGON_WINDING);
    return positions;
  }

  if (!isSimple(polygon)) {
    let targetIndex = 0;

    for (const [polygonIndex, simplePolygon] of polygon.entries()) {
      targetIndex = copyNestedRing(positions, targetIndex, simplePolygon, positionSize, polygonIndex === 0 ? OUTER_POLYGON_WINDING : HOLE_POLYGON_WINDING);
      holeIndices.push(targetIndex);
    }

    holeIndices.pop();
    return {
      positions,
      holeIndices
    };
  }

  copyNestedRing(positions, 0, polygon, positionSize, OUTER_POLYGON_WINDING);
  return positions;
}

function getPlaneArea(positions, xIndex, yIndex) {
  const numVerts = positions.length / 3;
  let area = 0;

  for (let i = 0; i < numVerts; i++) {
    const j = (i + 1) % numVerts;
    area += positions[i * 3 + xIndex] * positions[j * 3 + yIndex];
    area -= positions[j * 3 + xIndex] * positions[i * 3 + yIndex];
  }

  return Math.abs(area / 2);
}

function permutePositions(positions, xIndex, yIndex, zIndex) {
  const numVerts = positions.length / 3;

  for (let i = 0; i < numVerts; i++) {
    const o = i * 3;
    const x = positions[o + 0];
    const y = positions[o + 1];
    const z = positions[o + 2];
    positions[o + xIndex] = x;
    positions[o + yIndex] = y;
    positions[o + zIndex] = z;
  }
}

export function getSurfaceIndices(polygon, positionSize, preproject, full3d) {
  let holeIndices = getHoleIndices(polygon);

  if (holeIndices) {
    holeIndices = holeIndices.map(positionIndex => positionIndex / positionSize);
  }

  let positions = getPositions(polygon);
  const is3d = full3d && positionSize === 3;

  if (preproject) {
    const n = positions.length;
    positions = positions.slice();
    const p = [];

    for (let i = 0; i < n; i += positionSize) {
      p[0] = positions[i];
      p[1] = positions[i + 1];

      if (is3d) {
        p[2] = positions[i + 2];
      }

      const xy = preproject(p);
      positions[i] = xy[0];
      positions[i + 1] = xy[1];

      if (is3d) {
        positions[i + 2] = xy[2];
      }
    }
  }

  if (is3d) {
    const xyArea = getPlaneArea(positions, 0, 1);
    const xzArea = getPlaneArea(positions, 0, 2);
    const yzArea = getPlaneArea(positions, 1, 2);

    if (!xyArea && !xzArea && !yzArea) {
      return [];
    }

    if (xyArea > xzArea && xyArea > yzArea) {} else if (xzArea > yzArea) {
      if (!preproject) {
        positions = positions.slice();
      }

      permutePositions(positions, 0, 2, 1);
    } else {
      if (!preproject) {
        positions = positions.slice();
      }

      permutePositions(positions, 1, 2, 0);
    }
  }

  return earcut(positions, holeIndices, positionSize);
}
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