mat3.c

#include <stdlib.h>
#include <math.h>

#include "gl-matrix.h"

mat3_t mat3_create(mat3_t mat) {
    mat3_t dest = calloc(sizeof(double), 9);

    if (mat) {
        dest[0] = mat[0];
        dest[1] = mat[1];
        dest[2] = mat[2];
        dest[3] = mat[3];
        dest[4] = mat[4];
        dest[5] = mat[5];
        dest[6] = mat[6];
        dest[7] = mat[7];
        dest[8] = mat[8];
    }

    return dest;
}

mat3_t mat3_set(mat3_t mat, mat3_t dest) {
    dest[0] = mat[0];
    dest[1] = mat[1];
    dest[2] = mat[2];
    dest[3] = mat[3];
    dest[4] = mat[4];
    dest[5] = mat[5];
    dest[6] = mat[6];
    dest[7] = mat[7];
    dest[8] = mat[8];
    return dest;
}

mat3_t mat3_identity(mat3_t dest) {
    if (!dest) { dest = mat3_create(NULL); }
    dest[0] = 1;
    dest[1] = 0;
    dest[2] = 0;
    dest[3] = 0;
    dest[4] = 1;
    dest[5] = 0;
    dest[6] = 0;
    dest[7] = 0;
    dest[8] = 1;
    return dest;
}

mat3_t mat3_transpose(mat3_t mat, mat3_t dest) {
    // If we are transposing ourselves we can skip a few steps but have to cache some values
    if (!dest || mat == dest) {
        double a01 = mat[1], a02 = mat[2],
            a12 = mat[5];

        mat[1] = mat[3];
        mat[2] = mat[6];
        mat[3] = a01;
        mat[5] = mat[7];
        mat[6] = a02;
        mat[7] = a12;
        return mat;
    }

    dest[0] = mat[0];
    dest[1] = mat[3];
    dest[2] = mat[6];
    dest[3] = mat[1];
    dest[4] = mat[4];
    dest[5] = mat[7];
    dest[6] = mat[2];
    dest[7] = mat[5];
    dest[8] = mat[8];
    return dest;
}

mat4_t mat3_toMat4(mat3_t mat, mat4_t dest) {
    if (!dest) { dest = mat4_create(NULL); }

    dest[15] = 1;
    dest[14] = 0;
    dest[13] = 0;
    dest[12] = 0;

    dest[11] = 0;
    dest[10] = mat[8];
    dest[9] = mat[7];
    dest[8] = mat[6];

    dest[7] = 0;
    dest[6] = mat[5];
    dest[5] = mat[4];
    dest[4] = mat[3];

    dest[3] = 0;
    dest[2] = mat[2];
    dest[1] = mat[1];
    dest[0] = mat[0];

    return dest;
}