Function xQuatFromMat

src/SB/Core/x/xMath3.cpp:553–600

Matching in Ratatouille, minus debug stuff: https://decomp.me/scratch/VthMZ

// Matching in Ratatouille, minus debug stuff: https://decomp.me/scratch/VthMZ
void xQuatFromMat(xQuat* q, const xMat3x3* m)
{
    F32* mp = (F32*)m;
    F32* qvp = (F32*)q;
    F32 tr = m->right.x + m->up.y + m->at.z;
    F32 root;

    if (tr > 0.0f)
    {
        root = xsqrt(1.0f + tr);
        q->s = 0.5f * root;
        root = 0.5f / root;
        q->v.x = root * (m->at.y - m->up.z);
        q->v.y = root * (m->right.z - m->at.x);
        q->v.z = root * (m->up.x - m->right.y);
    }
    else
    {
        static S32 nxt[3] = { 1, 2, 0 };

        S32 i = 0;
        if (mp[5] > mp[0])
            i = 1;
        if (mp[10] > mp[i * 5])
            i = 2;

        S32 j = nxt[i];
        S32 k = nxt[j];

        root = xsqrt(mp[i * 5] - mp[j * 5] - mp[k * 5] + 1.0f);
        if (xabs(root) < 1e-5f)
        {
            xQuatCopy(q, &g_IQ);
            return;
        }

        qvp[i] = 0.5f * root;
        root = 0.5f / root;
        q->s = root * (mp[j + k * 4] - mp[k + j * 4]);
        qvp[j] = root * (mp[i + j * 4] + mp[j + i * 4]);
        qvp[k] = root * (mp[i + k * 4] + mp[k + i * 4]);

        if (q->s < 0.0f)
        {
            xQuatFlip(q, q);
        }
    }
}

void xQuatFromAxisAngle(xQuat* q, const xVec3* a, F32 t)
{