✨ Add realtime preview

- Preview quality is crude but works good enough.
- Add scaling to render function. This helps to make the preview
  faster because we can use the same result for several pixels.
- You can move around the camera a bit with wasd, super basic.
- Press R to start/stop rendering the scene.

1 files changed, 17 insertions, 1 deletions

diff --git a/racer-tracer/src/camera.rs b/racer-tracer/src/camera.rs
index 2c7be12..45d2919 100644
--- a/racer-tracer/src/camera.rs
+++ b/racer-tracer/src/camera.rs
@@ -33,9 +33,25 @@ impl Camera {
     }
 
     pub fn get_ray(&self, u: f64, v: f64) -> Ray {
+        let upper_left_corner = self.origin + self.vertical / 2.0
+            - self.horizontal / 2.0
+            - Vec3::new(0.0, 0.0, self.focal_length);
+
         Ray::new(
             self.origin,
-            self.upper_left_corner + u * self.horizontal - v * self.vertical - self.origin,
+            upper_left_corner + u * self.horizontal - v * self.vertical - self.origin,
         )
     }
+
+    // TODO: Add support for rotation
+
+    // TODO: Use forward facing vector
+    pub fn go_forward(&mut self, go: f64) {
+        self.origin += Vec3::new(0.0, 0.0, go);
+    }
+
+    // TODO: Use right facing vector
+    pub fn go_right(&mut self, go: f64) {
+        self.origin += Vec3::new(go, 0.0, 0.0);
+    }
 }