numpy - vec3 transformation mat4

vec3-mat4.py

import numpy as np


def cube_geometry(x, y, z):
    xSize = x / 2
    ySize = y / 2
    zSize = z / 2
    positions = np.array([
        [-xSize, ySize, zSize], [xSize, ySize, zSize],
        [-xSize, -ySize, zSize], [xSize, -ySize, zSize],
        [xSize, ySize, -zSize], [-xSize, ySize, -zSize],
        [xSize, -ySize, -zSize], [-xSize, -ySize, -zSize],
        [-xSize, ySize, -zSize], [-xSize, ySize, zSize],
        [-xSize, -ySize, -zSize], [-xSize, -ySize, zSize],
        [xSize, ySize, zSize], [xSize, ySize, -zSize],
        [xSize, -ySize, zSize], [xSize, -ySize, -zSize],
        [-xSize, ySize, -zSize], [xSize, ySize, -zSize],
        [-xSize, ySize, zSize], [xSize, ySize, zSize],
        [-xSize, -ySize, zSize], [xSize, -ySize, zSize],
        [-xSize, -ySize, -zSize], [xSize, -ySize, -zSize]
    ])
    normals = np.array([
        [0, 0, 1], [0, 0, 1],
        [0, 0, 1], [0, 0, 1],
        [0, 0, -1], [0, 0, -1],
        [0, 0, -1], [0, 0, -1],
        [-1, 0, 0], [-1, 0, 0],
        [-1, 0, 0], [-1, 0, 0],
        [1, 0, 0], [1, 0, 0],
        [1, 0, 0], [1, 0, 0],
        [0, 1, 0], [0, 1, 0],
        [0, 1, 0], [0, 1, 0],
        [0, -1, 0], [0, -1, 0],
        [0, -1, 0], [0, -1, 0]
    ])
    uvs = np.array([
        [0, 1], [1, 1], [0, 0],
        [1, 0], [0, 1], [1, 1],
        [0, 0], [1, 0], [0, 1],
        [1, 1], [0, 0], [1, 0],
        [0, 1], [1, 1], [0, 0],
        [1, 0], [0, 1], [1, 1],
        [0, 0], [1, 0], [0, 1],
        [1, 1], [0, 0], [1, 0]
    ])
    cells = np.array([
        [0, 2, 3], [0, 3, 1],
        [4, 6, 7], [4, 7, 5],
        [8, 10, 11], [8, 11, 9],
        [12, 14, 15], [12, 15, 13],
        [16, 18, 19], [16, 19, 17],
        [20, 22, 23], [20, 23, 21]
    ])

    return positions, cells, normals, uvs


def transform_vec3_mat4(a: np.ndarray, _m: np.ndarray):
    """
        Transforms the vec3 with a mat4.
        4th vector component is implicitly '1'

        Reference:
        https://en.wikipedia.org/wiki/Transformation_matrix#Examples_in_3D_computer_graphics
        http://math.hws.edu/graphicsbook/c3/transform-matrices-3d.png

        Code from:
        https://github.com/stackgl/gl-vec3/blob/master/transformMat4.js

        :param a: (3) -- float64
                  3 dimensions vector
        :param m: (4, 4) -- float64
                  Mat 4x4 representing a transformation in 3D cartesian space
        :return: (3) -- float64
                 transfromed vec3
        """

    m = _m.flatten()

    x = a[0]
    y = a[1]
    z = a[2]

    w = m[3] * x + m[7] * y + m[11] * z + m[15]
    w = w or 1.0

    out = np.array([
        (m[0] * x + m[4] * y + m[8] * z + m[12]) / w,
        (m[1] * x + m[5] * y + m[9] * z + m[13]) / w,
        (m[2] * x + m[6] * y + m[10] * z + m[14]) / w
    ])

    return out


def transform_points(array: np.ndarray, mat: np.ndarray):
    return np.array([transform_vec3_mat4(point, mat) for point in array])


positions, cells, normals, uvs = cube_geometry(1, 1, 1)

vx = 0.5
vy = 0
vz = 0

translate = np.array([
    1, 0, 0, 0,
    0, 1, 0, 0,
    0, 0, 1, 0,
    vx, vy, vz, 1,
])

positionsTranslated = transform_points(positions, translate)
print(positions)
print(positionsTranslated)

"""
result:

[[-0.5  0.5  0.5]
 [ 0.5  0.5  0.5]
 [-0.5 -0.5  0.5]
 [ 0.5 -0.5  0.5]
 [ 0.5  0.5 -0.5]
 [-0.5  0.5 -0.5]
 [ 0.5 -0.5 -0.5]
 [-0.5 -0.5 -0.5]
 [-0.5  0.5 -0.5]
 [-0.5  0.5  0.5]
 [-0.5 -0.5 -0.5]
 [-0.5 -0.5  0.5]
 [ 0.5  0.5  0.5]
 [ 0.5  0.5 -0.5]
 [ 0.5 -0.5  0.5]
 [ 0.5 -0.5 -0.5]
 [-0.5  0.5 -0.5]
 [ 0.5  0.5 -0.5]
 [-0.5  0.5  0.5]
 [ 0.5  0.5  0.5]
 [-0.5 -0.5  0.5]
 [ 0.5 -0.5  0.5]
 [-0.5 -0.5 -0.5]
 [ 0.5 -0.5 -0.5]]
[[ 0.   0.5  0.5]
 [ 1.   0.5  0.5]
 [ 0.  -0.5  0.5]
 [ 1.  -0.5  0.5]
 [ 1.   0.5 -0.5]
 [ 0.   0.5 -0.5]
 [ 1.  -0.5 -0.5]
 [ 0.  -0.5 -0.5]
 [ 0.   0.5 -0.5]
 [ 0.   0.5  0.5]
 [ 0.  -0.5 -0.5]
 [ 0.  -0.5  0.5]
 [ 1.   0.5  0.5]
 [ 1.   0.5 -0.5]
 [ 1.  -0.5  0.5]
 [ 1.  -0.5 -0.5]
 [ 0.   0.5 -0.5]
 [ 1.   0.5 -0.5]
 [ 0.   0.5  0.5]
 [ 1.   0.5  0.5]
 [ 0.  -0.5  0.5]
 [ 1.  -0.5  0.5]
 [ 0.  -0.5 -0.5]
 [ 1.  -0.5 -0.5]]

"""