@woosh/meep-engine/src/engine/graphics/geometry/computeMeshSurfaceArea.js

Pure JavaScript game engine. Fully featured and production ready.

import { assert } from "../../../core/assert.js";
import { compute_triangle_area_3d } from "../../../core/geom/3d/triangle/compute_triangle_area_3d.js";

/**
 *
 * @param {Float32Array} result Area of individual polygons will be written here
 * @param {number[]|Float32Array} points
 * @param {number[]|Uint8Array|Uint16Array|Uint32Array} indices
 * @param {number} [polygon_count]
 * @returns {number} total surface area
 */
export function computeMeshSurfaceArea(result, points, indices, polygon_count = indices.length / 3) {
    assert.lessThanOrEqual(polygon_count, indices.length / 3, "index underflow");

    let total = 0;

    for (let i = 0; i < polygon_count; i++) {
        const index3 = i * 3;

        const a = indices[index3];
        const b = indices[index3 + 1];
        const c = indices[index3 + 2];

        //read points
        const a3 = a * 3;

        const x0 = points[a3];
        const y0 = points[a3 + 1];
        const z0 = points[a3 + 2];

        const b3 = b * 3;

        const x1 = points[b3];
        const y1 = points[b3 + 1];
        const z1 = points[b3 + 2];

        const c3 = c * 3;

        const x2 = points[c3];
        const y2 = points[c3 + 2];
        const z2 = points[c3 + 2];

        const area = compute_triangle_area_3d(x0, y0, z0, x1, y1, z1, x2, y2, z2);

        assert.notNaN(area, "area");

        result[i] = area;

        total += area;
    }

    return total;
}