@woosh/meep-engine/src/core/geom/3d/frustum/hexahedron_from_aabb.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 * Constructs an orthographic hexahedron from an Axis-Aligned Bounding Box.
 * The planes are stored as 4-tuples (nx, ny, nz, d).
 *
 * Normals are facing inwards, i.e., the volume of positive.
 *
 * This can also be used for an orthographic camera frustum.
 *
 * @param {Float32Array|number[]} output
 * @param {number} output_offset
 * @param {number} x0 - Minimum X
 * @param {number} y0 - Minimum Y
 * @param {number} z0 - Minimum Z
 * @param {number} x1 - Maximum X
 * @param {number} y1 - Maximum Y
 * @param {number} z1 - Maximum Z
 */
export function hexahedron_from_aabb(
    output,
    output_offset,
    x0, y0, z0,
    x1, y1, z1
){
    
    // Right plane (x = x1): Normal points -X
    output[output_offset + 0] = -1;
    output[output_offset + 1] = 0;
    output[output_offset + 2] = 0;
    output[output_offset + 3] = x1;

    // Left plane (x = x0): Normal points +X
    output[output_offset + 4] = 1;
    output[output_offset + 5] = 0;
    output[output_offset + 6] = 0;
    output[output_offset + 7] = -x0;

    // Top plane (y = y1): Normal points -Y
    output[output_offset + 8] = 0;
    output[output_offset + 9] = -1;
    output[output_offset + 10] = 0;
    output[output_offset + 11] = y1;

    // Bottom plane (y = y0): Normal points +Y
    output[output_offset + 12] = 0;
    output[output_offset + 13] = 1;
    output[output_offset + 14] = 0;
    output[output_offset + 15] = -y0;

    // Near plane (z = z0): Normal points +Z
    output[output_offset + 16] = 0;
    output[output_offset + 17] = 0;
    output[output_offset + 18] = 1;
    output[output_offset + 19] = -z0;

    // Far plane (z = z1): Normal points -Z
    output[output_offset + 20] = 0;
    output[output_offset + 21] = 0;
    output[output_offset + 22] = -1;
    output[output_offset + 23] = z1;
}