function Xrot(angle)
    local cos = math.cos(angle)
    local sin = math.sin(angle)
    local yy=y*cos - z*sin
    local zz=z*cos + y*sin
    y=yy
    z=zz
end

function matrix4x4:SetRotation(flAngle,v)
    -- Normalize beforehand
    v = v:normalize()

    -- c = math.cos(angle), s = math.sin(angle), t = (1-c)
    -- [ xxt+c   xyt-zs  xzt+ys ]
    -- [ yxt+zs  yyt+c   yzt-xs ]
    -- [ zxt-ys  zyt+xs  zzt+c  ]

    local x = v.x
    local y = v.y
    local z = v.z
    local rot = math.rad(flAngle)
    local c = math.cos(rot)
    local s = math.sin(rot)
    local t = 1-c

    m[1].x = x*x*t + c
    m[2].x = x*y*t - z*s
    m[3].x = x*z*t + y*s

    m[1].y = y*x*t + z*s
    m[2].y = y*y*t + c
    m[3].y = y*z*t - x*s

    m[1].z = z*x*t - y*s
    m[2].z = z*y*t + x*s
    m[3].z = z*z*t + c
end