// ExtractEulerAngles extracts the rotation part of the matrix as Euler angle rotation values.
func (mat *T) ExtractEulerAngles() (yHead, xPitch, zRoll float32) {
xPitch = math.Asin(mat[1][2])
f12 := math.Abs(mat[1][2])
if f12 > (1.0-0.0001) && f12 < (1.0+0.0001) { // f12 == 1.0
yHead = 0.0
zRoll = math.Atan2(mat[0][1], mat[0][0])
} else {
yHead = math.Atan2(-mat[0][2], mat[2][2])
zRoll = math.Atan2(-mat[1][0], mat[1][1])
}
return yHead, xPitch, zRoll
}
// Angle returns the counter-clockwise angle of the vector from the x axis.
func (vec *T) Angle() float32 {
return math.Atan2(vec[1], vec[0])
}