diff --git a/src/geometry/isometry.rs b/src/geometry/isometry.rs index 7a630bed..7e4b703d 100755 --- a/src/geometry/isometry.rs +++ b/src/geometry/isometry.rs @@ -210,6 +210,28 @@ where self.translation.vector = self.rotation.transform_vector(&self.translation.vector); } + /// Computes `self.inverse() * rhs` in a more efficient way. + /// + /// # Example + /// + /// ``` + /// # use std::f32; + /// # use nalgebra::{Isometry2, Point2, Vector2}; + /// let mut iso1 = Isometry2::new(Vector2::new(1.0, 2.0), f32::consts::FRAC_PI_2); + /// let mut iso2 = Isometry2::new(Vector2::new(10.0, 20.0), f32::consts::FRAC_PI_4); + /// + /// assert_eq!(iso1.inverse() * iso2, iso1.inv_mul(&iso2)); + /// ``` + #[inline] + pub fn inv_mul(&self, rhs: &Isometry) -> Self { + let inv_rot1 = self.rotation.inverse(); + let tr_12 = rhs.translation.vector.clone() - self.translation.vector.clone(); + Isometry::from_parts( + inv_rot1.transform_vector(&tr_12).into(), + inv_rot1 * rhs.rotation.clone(), + ) + } + /// Appends to `self` the given translation in-place. /// /// # Example