mat4: nml::mat4& operator*=(const nml::mat4& other)

Multiply to the current mat4 by a mat4.

The product between two mat4 is calculated this way:

\(\begin{bmatrix} x.x & y.x & z.x & w.x \\ x.y & y.y & z.y & w.y \\ x.z & y.z & z.z & w.z \\ x.w & y.w & z.w & w.w \end{bmatrix} * \begin{bmatrix} other.x.x & other.y.x & other.z.x & other.w.x \\ other.x.y & other.y.y & other.z.y & other.w.y \\ other.x.z & other.y.z & other.z.z & other.w.z \\ other.x.w & other.y.w & other.z.w & other.w.w \end{bmatrix} =\)

\(\begin{bmatrix} a & e & i & m \\ b & f & j & n \\ c & g & k & o \\ d & h & l & p \end{bmatrix}\)

\(\small a = x.x * other.x.x + y.x * other.x.y + z.x * other.x.z + w.x * other.x.w\) \(\small b = x.x * other.y.x + y.x * other.y.y + z.x * other.y.z + w.x * other.y.w\) \(\small c = x.x * other.z.x + y.x * other.z.y + z.x * other.z.z + w.x * other.z.w\) \(\small d = x.x * other.w.x + y.x * other.w.y + z.x * other.w.z + w.x * other.w.w\) \(\small e = x.y * other.x.x + y.y * other.x.y + z.y * other.x.z + w.y * other.x.w\) \(\small f = x.y * other.y.x + y.y * other.y.y + z.y * other.y.z + w.y * other.y.w\) \(\small g = x.y * other.z.x + y.y * other.z.y + z.y * other.z.z + w.y * other.z.w\) \(\small h = x.y * other.w.x + y.y * other.w.y + z.y * other.w.z + w.y * other.w.w\) \(\small i = x.z * other.x.x + y.z * other.x.y + z.z * other.x.z + w.z * other.x.w\) \(\small j = x.z * other.y.x + y.z * other.y.y + z.z * other.y.z + w.z * other.y.w\) \(\small k = x.z * other.z.x + y.z * other.z.y + z.z * other.z.z + w.z * other.z.w\) \(\small l = x.z * other.w.x + y.z * other.w.y + z.z * other.w.z + w.z * other.w.w\) \(\small m = x.w * other.x.x + y.w * other.x.y + z.w * other.x.z + w.w * other.x.w\) \(\small n = x.w * other.y.x + y.w * other.y.y + z.w * other.y.z + w.w * other.y.w\) \(\small o = x.w * other.z.x + y.w * other.z.y + z.w * other.z.z + w.w * other.z.w\) \(\small p = x.w * other.w.x + y.w * other.w.y + z.w * other.w.z + w.w * other.w.w\)

Example

#include "include/mat4.h"
#include <iostream>

int main() {
        nml::mat4 a(2.0f, 0.0f, 0.0f, 0.0f, 0.0f, 2.0f, 0.0f, 0.0f, 0.0f, 0.0f, 2.0f, 0.0f, 0.0f, 0.0f, 0.0f, 2.0f);
        nml::mat4 b = nml::inverse(a);
        a *= b;
        std::cout << nml::to_string(a) << std::endl;

        return 0;
}

Result:

[[1.000000, 0.000000, 0.000000, 0.000000], [0.000000, 1.000000, 0.000000, 0.000000], [0.000000, 0.000000, 1.000000, 0.000000], [0.000000, 0.000000, 0.000000, 1.000000]]