feat(engine): make camera look at a target position

1 files changed, 97 insertions, 0 deletions

diff --git a/engine/src/vector.rs b/engine/src/vector.rs
index c25a258..88a8198 100644
--- a/engine/src/vector.rs
+++ b/engine/src/vector.rs
@@ -1,3 +1,5 @@
+use std::ops::{Neg, Sub};
+
 #[derive(Debug)]
 pub struct Vec2<Value>
 {
@@ -18,3 +20,98 @@ pub struct Vec3<Value>
     pub y: Value,
     pub z: Value,
 }
+
+impl Vec3<f32>
+{
+    pub const UP: Self = Self {
+        x: 0.0,
+        y: 1.0,
+        z: 0.0,
+    };
+
+    /// Returns the length of the vector.
+    #[must_use]
+    pub fn length(&self) -> f32
+    {
+        (self.x.powi(2) + self.y.powi(2) + self.z.powi(2)).sqrt()
+    }
+
+    /// Normalizes the vector, returning a unit vector.
+    #[must_use]
+    pub fn normalize(&self) -> Self
+    {
+        let length = self.length();
+
+        Self {
+            x: self.x / length,
+            y: self.y / length,
+            z: self.z / length,
+        }
+    }
+
+    /// Returns the cross product of this and another vector.
+    #[must_use]
+    pub fn cross(&self, rhs: &Self) -> Self
+    {
+        Self {
+            x: (self.y * rhs.z) - (self.z * rhs.y),
+            y: (self.z * rhs.x) - (self.x * rhs.z),
+            z: (self.x * rhs.y) - (self.y * rhs.x),
+        }
+    }
+
+    /// Returns the dot product of this and another vector.
+    #[must_use]
+    pub fn dot(&self, rhs: &Self) -> f32
+    {
+        (self.x * rhs.x) + (self.y * rhs.y) + (self.z * rhs.z)
+    }
+}
+
+impl<Value> Sub for Vec3<Value>
+where
+    Value: Sub<Value, Output = Value>,
+{
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output
+    {
+        Self::Output {
+            x: self.x - rhs.x,
+            y: self.y - rhs.y,
+            z: self.z - rhs.z,
+        }
+    }
+}
+
+impl<Value> Sub for &Vec3<Value>
+where
+    for<'a, 'b> &'a Value: Sub<&'b Value, Output = Value>,
+{
+    type Output = Vec3<Value>;
+
+    fn sub(self, rhs: Self) -> Self::Output
+    {
+        Self::Output {
+            x: &self.x - &rhs.x,
+            y: &self.y - &rhs.y,
+            z: &self.z - &rhs.z,
+        }
+    }
+}
+
+impl<Value> Neg for Vec3<Value>
+where
+    Value: Neg<Output = Value>,
+{
+    type Output = Self;
+
+    fn neg(mut self) -> Self::Output
+    {
+        self.x = -self.x;
+        self.y = -self.y;
+        self.z = -self.z;
+
+        self
+    }
+}