@woosh/meep-engine/src/engine/graphics/ecs/path/tube/build/StreamGeometryBuilder.js

Pure JavaScript game engine. Fully featured and production ready.

import { UintArrayForCount } from "../../../../../../core/collection/array/typed/uint_array_for_count.js";
import { BufferAttribute, BufferGeometry } from "three";

/**
 * Helper class, allowing us to treat geometry build process as a stream without having to create intermediate arrays and performing unnecessary copying
 */
export class StreamGeometryBuilder {
    constructor() {
        /**
         *
         * @type {number}
         */
        this.cursor_vertices = 0;

        /**
         *
         * @type {number}
         */
        this.cursor_indices = 0;

        /**
         *
         * @type {Float32Array|number[]|null}
         * @private
         */
        this.__vertex_positions = null;
        /**
         *
         * @type {Float32Array|number[]|null}
         * @private
         */
        this.__vertex_normals = null;
        /**
         *
         * @type {Float32Array|number[]|null}
         * @private
         */
        this.__vertex_uvs = null;
        /**
         *
         * @type {Uint8Array|Uint16Array|Uint32Array|number[]|null}
         * @private
         */
        this.__indices = null;
    }

    get positions() {
        return this.__vertex_positions;
    }

    get normals() {
        return this.__vertex_normals;
    }

    get uvs() {
        return this.__vertex_uvs;
    }

    get indices() {
        return this.__indices;
    }

    /**
     *
     * @param {number} vertex_count
     * @param {number} polygon_count
     */
    allocate(vertex_count, polygon_count) {
        this.__vertex_positions = new Float32Array(vertex_count * 3);
        this.__vertex_normals = new Float32Array(vertex_count * 3);
        this.__vertex_uvs = new Float32Array(vertex_count * 2);

        const INDEX_BUFFER_CLASS = UintArrayForCount(vertex_count);
        this.__indices = new INDEX_BUFFER_CLASS(polygon_count * 3);
    }

    /**
     * @returns {THREE.BufferGeometry}
     */
    build() {
        const geometry = new BufferGeometry();

        geometry.setIndex(new BufferAttribute(this.__indices, 1));
        geometry.setAttribute('position', new BufferAttribute(this.__vertex_positions, 3));
        geometry.setAttribute('normal', new BufferAttribute(this.__vertex_normals, 3));
        geometry.setAttribute('uv', new BufferAttribute(this.__vertex_uvs, 2));

        return geometry;
    }
}