cross: Vec3: implement rotate_{xy,xz,yz} operations

crates/cross/src/vec.rs

@@ -253,6 +253,22 @@ impl<R: Real> Vec3<R> {
     pub fn with_xy(&self, xy: Vec2<R>) -> Self {
         Self::new(xy.x(), xy.y(), self.z())
     }
+    pub fn xz(&self) -> Vec2<R> {
+        Vec2::new(self.x(), self.z())
+    }
+    pub fn with_xz(&self, xz: Vec2<R>) -> Self {
+        // NB: the `Vec2` type calls these coordinates `x` and `y`
+        // even though they represent `x` and `z` in this context.
+        Self::new(xz.x(), self.y(), xz.y())
+    }
+    pub fn yz(&self) -> Vec2<R> {
+        Vec2::new(self.y(), self.z())
+    }
+    pub fn with_yz(&self, yz: Vec2<R>) -> Self {
+        // NB: the `Vec2` type calls these coordinates `x` and `y`
+        // even though they represent `y` and `z` in this context.
+        Self::new(self.x(), yz.x(), yz.y())
+    }
 
     pub fn distance(&self, other: Self) -> R {
         (*self - other).mag()
@@ -365,6 +381,25 @@ impl<R: Real> Vec3<R> {
     pub fn floor(&self) -> Self {
         Self::new(self.x().floor(), self.y().floor(), self.z().floor())
     }
+
+    /// rotate in the xy plane
+    pub fn rotate_xy(&self, angle: R) -> Self {
+        self.with_xy(
+            self.xy().rotate(angle)
+        )
+    }
+    /// rotate in the xz plane
+    pub fn rotate_xz(&self, angle: R) -> Self {
+        self.with_xz(
+            self.xz().rotate(angle)
+        )
+    }
+    /// rotate in the yz plane
+    pub fn rotate_yz(&self, angle: R) -> Self {
+        self.with_yz(
+            self.yz().rotate(angle)
+        )
+    }
 }
 
 impl<R> Into<(R, R, R)> for Vec3<R> {