@woosh/meep-engine/src/core/geom/3d/cone/computeConeBoundingBox.js

Pure JavaScript game engine. Fully featured and production ready.

import { max2 } from "../../../math/max2.js";
import { min2 } from "../../../math/min2.js";
import { v3_angle_between } from "../../vec3/v3_angle_between.js";

/**
 * NOTE: used stackoverflow answer as a basis for circle part: https://stackoverflow.com/questions/2592011/bounding-boxes-for-circle-and-arcs-in-3d
 * @param {number[]|ArrayLike<number>|Float32Array} result
 * @param {number} originX
 * @param {number} originY
 * @param {number} originZ
 * @param {number} directionX
 * @param {number} directionY
 * @param {number} directionZ
 * @param {number} angle in Radians
 * @param {number} length
 */
export function computeConeBoundingBox(
    result,
    originX, originY, originZ,
    directionX, directionY, directionZ,
    angle,
    length
) {

    const ax = v3_angle_between(directionX, directionY, directionZ, 1, 0, 0);
    const ay = v3_angle_between(directionX, directionY, directionZ, 0, 1, 0);
    const az = v3_angle_between(directionX, directionY, directionZ, 0, 0, 1);

    //compute radius of the base of the cone
    const radius = length * Math.tan(angle);

    //compute cone base center
    const centerX = originX + directionX * length;
    const centerY = originY + directionY * length;
    const centerZ = originZ + directionZ * length;

    const rX = Math.sin(ax) * radius;
    const rY = Math.sin(ay) * radius;
    const rZ = Math.sin(az) * radius;

    //compute cone base bounds
    const cx0 = centerX - rX;
    const cy0 = centerY - rY;
    const cz0 = centerZ - rZ;

    const cx1 = centerX + rX;
    const cy1 = centerY + rY;
    const cz1 = centerZ + rZ;

    //combine bounds of the origin and base of the cone
    result[0] = min2(originX, cx0);
    result[1] = min2(originY, cy0);
    result[2] = min2(originZ, cz0);

    result[3] = max2(originX, cx1);
    result[4] = max2(originY, cy1);
    result[5] = max2(originZ, cz1);
}