correction orbital camera inputs

docs/user/camera-input.md

@@ -49,6 +49,13 @@ ctrl.apply_to(app.scene.camera_mut());  // write the framing into the active cam
 `CameraController::from_camera(&cam)` rebuilds a controller from an existing camera
 (useful to start the orbit from a manual framing).
 
+Two public fields tune the feel of the camera (defaults in parentheses):
+
+| Field | Meaning | Default |
+|-------|---------|---------|
+| `orbit_sensitivity` | radians of yaw per pixel of mouse delta | `0.005` (~110° per full window width) |
+| `zoom_factor` | multiplicative distance change per wheel notch (`distance *= factor^scroll`) | `0.9` (10% per notch) |
+
 The exact wiring snippet (orbit + zoom + reset + `1`/`2`/`3` presets, driven from
 `app.input`) is in [`demo.rs`](../../lib/examples/demo.rs), `update()` section.
 
@@ -64,7 +71,13 @@ every frame (`begin_frame`/`end_frame` around your `update`). Three semantics pe
 | **released** | `key_released(code)`, `mouse_button_released(btn)` | true **only** on the release frame |
 
 Plus: `mouse_position() -> (f32, f32)`, `mouse_delta() -> (f32, f32)` (accumulated over the
-frame, reset between frames), `scroll_delta() -> (f32, f32)` (wheel).
+frame, reset between frames), `scroll_delta() -> (f32, f32)` (wheel, in **line/notch units** —
+`PixelDelta` events are normalized by /32 so one physical wheel notch ≈ 1.0 on every backend).
+
+> **Button-gated orbit**: `mouse_delta()` returns movement *whenever* the mouse moves. For a
+> classic arc-rotate camera, apply it only while a button is held — that is what the `demo` does:
+> `if app.input.mouse_button_held(MouseButton::Left) { self.camera.orbit(dx, dy); }`.
+> Free-movement orbit (no button) is also possible, just drop the condition.
 
 `KeyCode` values are winit's physical codes (`winit::keyboard::KeyCode`); mouse buttons are
 `winit::event::MouseButton`. The library does not re-export them: if your code mentions
@@ -73,12 +86,15 @@ applications (like `simple`/`cube`) don't need winit: `app.input` remains usable
 `KeyCode` comparisons require the import.
 
 ```rust
+use winit::event::MouseButton;
 use winit::keyboard::KeyCode;
 
 fn update(&mut self, app: &mut wsg_lib::App) {
-    // Orbit + zoom driven by the mouse (excerpts from demo):
+    // Orbit (left-drag gated) + zoom driven by the mouse (excerpts from demo):
     let (dx, dy) = app.input.mouse_delta();
-    self.camera.orbit(dx, dy);
+    if app.input.mouse_button_held(MouseButton::Left) {
+        self.camera.orbit(dx, dy);
+    }
     let (_, sy) = app.input.scroll_delta();
     self.camera.zoom(sy);
 
@@ -103,6 +119,7 @@ fn update(&mut self, app: &mut wsg_lib::App) {
 | FPS camera (WASD) | `key_held(KeyCode::KeyW)` in `update` → move `camera.position`/`target`; override `render()` if needed |
 | Changing the orbit target | `ctrl.target = subject_position;` (following an object) |
 | View presets | `key_pressed(Digit1/2/3)` → write yaw/pitch/distance (from the `demo`) |
+| Tuning the camera speed | `ctrl.orbit_sensitivity = 0.003;` (slower orbit), `ctrl.zoom_factor = 0.95;` (gentler zoom) |
 
 ## Links