Flip image

Author: llGaetanll

TODO.md

@@ -81,8 +81,6 @@ Once CPU-side camera is working:
 
 ## Technical Debt
 
-1. [ ] **Ray tracer flips image left-to-right**: The interactive camera controls have inverted signs on movement and mouse look to compensate. The ray tracer appears to be rendering the image mirrored horizontally. The workaround is in `host/src/main.rs` (`update_camera`). The root cause should be investigated - likely in `Camera::new()` or `Camera::get_ray()` in `rtx-util/src/cam.rs`, possibly related to how pixel coordinates map to ray directions.
-
-2. [ ] **Crash when camera enters an object**: The program sometimes crashes, likely when the camera position moves inside geometry. This may cause issues with ray-object intersection tests (e.g., negative t values, NaN from inside-surface calculations). Needs investigation.
+1. [ ] **Crash when camera enters an object**: The program sometimes crashes, likely when the camera position moves inside geometry. This may cause issues with ray-object intersection tests (e.g., negative t values, NaN from inside-surface calculations). Needs investigation.
 
 2. [ ] `Array<T, N>` currently requires `T: Copy + Default` because we use `[Default::default(); N]` for initialization. This is overly restrictive. Ideally, `T` would only need to be "zeroable" (all zero bytes is a valid default). This would allow types like `Sphere` that aren't `Copy` but can be safely zero-initialized. The goal is something like `core::array::from_fn(|_| Default::default())` but in a form rust-gpu accepts.

crates/host/src/main.rs

@@ -144,7 +144,6 @@ impl RustShaderSandboxApp {
         self.last_cursor_y = self.cursor_y;
 
         // Update yaw/pitch from mouse (sensitivity factor)
-        // Signs inverted to compensate for ray tracer's left-right flip
         let sensitivity = 0.003;
         self.cam_yaw -= mouse_dx * sensitivity;
         self.cam_pitch -= mouse_dy * sensitivity;
@@ -163,7 +162,6 @@ impl RustShaderSandboxApp {
         let speed = 5.0 * dt;
 
         // Apply movement based on held keys
-        // Signs inverted to compensate for ray tracer's left-right flip
         if self.keys_held.w {
             self.cam_pos[0] += forward_x * speed;
             self.cam_pos[2] += forward_z * speed;

crates/rtx-util/src/cam.rs

@@ -121,8 +121,8 @@ impl Camera {
         let viewport_width = viewport_height * aspect_ratio;
 
         let w = (lookfrom - lookat).normalize();
-        let u = vup.cross(w).normalize();
-        let v = w.cross(u);
+        let u = w.cross(vup).normalize();
+        let v = u.cross(w);
 
         // Calculate the vectors across the horizontal and down the vertical viewport edges.
         let viewport_u = viewport_width * -u;