Scale camera zoom based on distance to target (#40)

* Scale camera zoom based on distance to target

* Fix screen2ray scaling with zoom

* Fix zoom_towards when point is not target

* Add zoom function

* Safety check

---------

Co-authored-by: Asger Nyman Christiansen <[email protected]>

src/camera.rs

@@ -298,6 +298,7 @@ impl Camera {
             Point3::from_vec(self.target),
             self.up,
         );
+        self.view[3][3] *= position.distance(target);
         self.update_screen2ray();
         self.update_frustrum();
     }
@@ -557,6 +558,7 @@ impl Camera {
 
     fn update_screen2ray(&mut self) {
         let mut v = self.view;
+        v /= v[3][3];
         if let ProjectionType::Perspective { .. } = self.projection_type {
             v[3] = vec4(0.0, 0.0, 0.0, 1.0);
         }
@@ -676,8 +678,17 @@ impl Camera {
         }
     }
 
+    ///
+    /// Moves the camera towards the camera target by the amount delta while keeping the given minimum and maximum distance to the target.
+    ///
+    pub fn zoom(&mut self, delta: f32, minimum_distance: f32, maximum_distance: f32) {
+        let target = self.target;
+        self.zoom_towards(&target, delta, minimum_distance, maximum_distance);
+    }
+
     ///
     /// Moves the camera towards the given point by the amount delta while keeping the given minimum and maximum distance to the point.
+    /// Note that the camera target is also updated so that the view direction is the same.
     ///
     pub fn zoom_towards(
         &mut self,
@@ -694,17 +705,15 @@ impl Camera {
 
         let position = *self.position();
         let distance = point.distance(position);
-        let direction = (point - position).normalize();
-        let target = *self.target();
-        let up = self.up;
-        let new_distance = (distance - delta).clamp(minimum_distance, maximum_distance);
-        let new_position = point - direction * new_distance;
-        self.set_view(new_position, new_position + (target - position), up);
-        if let ProjectionType::Orthographic { height } = self.projection_type() {
-            let h = new_distance * height / distance;
-            let z_near = self.z_near();
-            let z_far = self.z_far();
-            self.set_orthographic_projection(h, z_near, z_far);
+        if distance > f32::EPSILON {
+            let delta_clamped =
+                distance - (distance - delta).clamp(minimum_distance, maximum_distance);
+            let v = (point - position) * delta_clamped / distance;
+            self.set_view(
+                self.position + v,
+                self.target + v - v.project_on(self.view_direction()),
+                self.up,
+            );
         }
     }
 }