mapbox-gl/src/data/bucket/fill_extrusion_bucket.js

A WebGL interactive maps library

// @flow

import { FillExtrusionLayoutArray } from '../array_types';

import { members as layoutAttributes } from './fill_extrusion_attributes';
import SegmentVector from '../segment';
import { ProgramConfigurationSet } from '../program_configuration';
import { TriangleIndexArray } from '../index_array_type';
import EXTENT from '../extent';
import earcut from 'earcut';
import mvt from '@mapbox/vector-tile';
const vectorTileFeatureTypes = mvt.VectorTileFeature.types;
import classifyRings from '../../util/classify_rings';
import assert from 'assert';
const EARCUT_MAX_RINGS = 500;
import { register } from '../../util/web_worker_transfer';
import {hasPattern, addPatternDependencies} from './pattern_bucket_features';
import loadGeometry from '../load_geometry';
import EvaluationParameters from '../../style/evaluation_parameters';

import type {
    Bucket,
    BucketParameters,
    BucketFeature,
    IndexedFeature,
    PopulateParameters
} from '../bucket';

import type FillExtrusionStyleLayer from '../../style/style_layer/fill_extrusion_style_layer';
import type Context from '../../gl/context';
import type IndexBuffer from '../../gl/index_buffer';
import type VertexBuffer from '../../gl/vertex_buffer';
import type Point from '@mapbox/point-geometry';
import type {FeatureStates} from '../../source/source_state';
import type {ImagePosition} from '../../render/image_atlas';

const FACTOR = Math.pow(2, 13);

function addVertex(vertexArray, x, y, nx, ny, nz, t, e) {
    vertexArray.emplaceBack(
        // a_pos
        x,
        y,
        // a_normal_ed: 3-component normal and 1-component edgedistance
        Math.floor(nx * FACTOR) * 2 + t,
        ny * FACTOR * 2,
        nz * FACTOR * 2,
        // edgedistance (used for wrapping patterns around extrusion sides)
        Math.round(e)
    );
}

class FillExtrusionBucket implements Bucket {
    index: number;
    zoom: number;
    overscaling: number;
    layers: Array<FillExtrusionStyleLayer>;
    layerIds: Array<string>;
    stateDependentLayers: Array<FillExtrusionStyleLayer>;
    stateDependentLayerIds: Array<string>;

    layoutVertexArray: FillExtrusionLayoutArray;
    layoutVertexBuffer: VertexBuffer;

    indexArray: TriangleIndexArray;
    indexBuffer: IndexBuffer;

    hasPattern: boolean;
    programConfigurations: ProgramConfigurationSet<FillExtrusionStyleLayer>;
    segments: SegmentVector;
    uploaded: boolean;
    features: Array<BucketFeature>;

    constructor(options: BucketParameters<FillExtrusionStyleLayer>) {
        this.zoom = options.zoom;
        this.overscaling = options.overscaling;
        this.layers = options.layers;
        this.layerIds = this.layers.map(layer => layer.id);
        this.index = options.index;
        this.hasPattern = false;

        this.layoutVertexArray = new FillExtrusionLayoutArray();
        this.indexArray = new TriangleIndexArray();
        this.programConfigurations = new ProgramConfigurationSet(layoutAttributes, options.layers, options.zoom);
        this.segments = new SegmentVector();
        this.stateDependentLayerIds = this.layers.filter((l) => l.isStateDependent()).map((l) => l.id);

    }

    populate(features: Array<IndexedFeature>, options: PopulateParameters) {
        this.features = [];
        this.hasPattern = hasPattern('fill-extrusion', this.layers, options);

        for (const {feature, index, sourceLayerIndex} of features) {
            if (!this.layers[0]._featureFilter(new EvaluationParameters(this.zoom), feature)) continue;

            const geometry = loadGeometry(feature);

            const patternFeature: BucketFeature = {
                sourceLayerIndex,
                index,
                geometry,
                properties: feature.properties,
                type: feature.type,
                patterns: {}
            };

            if (typeof feature.id !== 'undefined') {
                patternFeature.id = feature.id;
            }

            if (this.hasPattern) {
                this.features.push(addPatternDependencies('fill-extrusion', this.layers, patternFeature, this.zoom, options));
            } else {
                this.addFeature(patternFeature, geometry, index, {});
            }

            options.featureIndex.insert(feature, geometry, index, sourceLayerIndex, this.index, true);
        }
    }

    addFeatures(options: PopulateParameters, imagePositions: {[string]: ImagePosition}) {
        for (const feature of this.features) {
            const {geometry} = feature;
            this.addFeature(feature, geometry, feature.index, imagePositions);
        }
    }

    update(states: FeatureStates, vtLayer: VectorTileLayer, imagePositions: {[string]: ImagePosition}) {
        if (!this.stateDependentLayers.length) return;
        this.programConfigurations.updatePaintArrays(states, vtLayer, this.stateDependentLayers, imagePositions);
    }

    isEmpty() {
        return this.layoutVertexArray.length === 0;
    }

    uploadPending() {
        return !this.uploaded || this.programConfigurations.needsUpload;
    }

    upload(context: Context) {
        if (!this.uploaded) {
            this.layoutVertexBuffer = context.createVertexBuffer(this.layoutVertexArray, layoutAttributes);
            this.indexBuffer = context.createIndexBuffer(this.indexArray);
        }
        this.programConfigurations.upload(context);
        this.uploaded = true;
    }

    destroy() {
        if (!this.layoutVertexBuffer) return;
        this.layoutVertexBuffer.destroy();
        this.indexBuffer.destroy();
        this.programConfigurations.destroy();
        this.segments.destroy();
    }

    addFeature(feature: BucketFeature, geometry: Array<Array<Point>>, index: number, imagePositions: {[string]: ImagePosition}) {
        for (const polygon of classifyRings(geometry, EARCUT_MAX_RINGS)) {
            let numVertices = 0;
            for (const ring of polygon) {
                numVertices += ring.length;
            }
            let segment = this.segments.prepareSegment(4, this.layoutVertexArray, this.indexArray);

            for (const ring of polygon) {
                if (ring.length === 0) {
                    continue;
                }

                if (isEntirelyOutside(ring)) {
                    continue;
                }

                let edgeDistance = 0;

                for (let p = 0; p < ring.length; p++) {
                    const p1 = ring[p];

                    if (p >= 1) {
                        const p2 = ring[p - 1];

                        if (!isBoundaryEdge(p1, p2)) {
                            if (segment.vertexLength + 4 > SegmentVector.MAX_VERTEX_ARRAY_LENGTH) {
                                segment = this.segments.prepareSegment(4, this.layoutVertexArray, this.indexArray);
                            }

                            const perp = p1.sub(p2)._perp()._unit();
                            const dist = p2.dist(p1);
                            if (edgeDistance + dist > 32768) edgeDistance = 0;

                            addVertex(this.layoutVertexArray, p1.x, p1.y, perp.x, perp.y, 0, 0, edgeDistance);
                            addVertex(this.layoutVertexArray, p1.x, p1.y, perp.x, perp.y, 0, 1, edgeDistance);

                            edgeDistance += dist;

                            addVertex(this.layoutVertexArray, p2.x, p2.y, perp.x, perp.y, 0, 0, edgeDistance);
                            addVertex(this.layoutVertexArray, p2.x, p2.y, perp.x, perp.y, 0, 1, edgeDistance);

                            const bottomRight = segment.vertexLength;

                            // ┌──────┐
                            // │ 0  1 │ Counter-clockwise winding order.
                            // │      │ Triangle 1: 0 => 2 => 1
                            // │ 2  3 │ Triangle 2: 1 => 2 => 3
                            // └──────┘
                            this.indexArray.emplaceBack(bottomRight, bottomRight + 2, bottomRight + 1);
                            this.indexArray.emplaceBack(bottomRight + 1, bottomRight + 2, bottomRight + 3);

                            segment.vertexLength += 4;
                            segment.primitiveLength += 2;
                        }
                    }
                }
            }

            if (segment.vertexLength + numVertices > SegmentVector.MAX_VERTEX_ARRAY_LENGTH) {
                segment = this.segments.prepareSegment(numVertices, this.layoutVertexArray, this.indexArray);
            }

            //Only triangulate and draw the area of the feature if it is a polygon
            //Other feature types (e.g. LineString) do not have area, so triangulation is pointless / undefined
            if (vectorTileFeatureTypes[feature.type] !== 'Polygon')
                continue;

            const flattened = [];
            const holeIndices = [];
            const triangleIndex = segment.vertexLength;

            for (const ring of polygon) {
                if (ring.length === 0) {
                    continue;
                }

                if (ring !== polygon[0]) {
                    holeIndices.push(flattened.length / 2);
                }

                for (let i = 0; i < ring.length; i++) {
                    const p = ring[i];

                    addVertex(this.layoutVertexArray, p.x, p.y, 0, 0, 1, 1, 0);

                    flattened.push(p.x);
                    flattened.push(p.y);
                }
            }

            const indices = earcut(flattened, holeIndices);
            assert(indices.length % 3 === 0);

            for (let j = 0; j < indices.length; j += 3) {
                // Counter-clockwise winding order.
                this.indexArray.emplaceBack(
                    triangleIndex + indices[j],
                    triangleIndex + indices[j + 2],
                    triangleIndex + indices[j + 1]);
            }

            segment.primitiveLength += indices.length / 3;
            segment.vertexLength += numVertices;
        }

        this.programConfigurations.populatePaintArrays(this.layoutVertexArray.length, feature, index, imagePositions);
    }
}

register('FillExtrusionBucket', FillExtrusionBucket, {omit: ['layers', 'features']});

export default FillExtrusionBucket;

function isBoundaryEdge(p1, p2) {
    return (p1.x === p2.x && (p1.x < 0 || p1.x > EXTENT)) ||
        (p1.y === p2.y && (p1.y < 0 || p1.y > EXTENT));
}

function isEntirelyOutside(ring) {
    return ring.every(p => p.x < 0) ||
        ring.every(p => p.x > EXTENT) ||
        ring.every(p => p.y < 0) ||
        ring.every(p => p.y > EXTENT);
}