Zoom with mouse button + motion (#129)

Author: Plonq

examples/advanced.rs

@@ -4,7 +4,7 @@
 //! Controls:
 //!   Orbit: Middle click
 //!   Pan: Shift + Middle click
-//!   Zoom: Mousewheel
+//!   Zoom: Mousewheel OR Right click + move mouse up/down
 
 use bevy::prelude::*;
 use bevy_panorbit_camera::{PanOrbitCamera, PanOrbitCameraPlugin, TouchControls};
@@ -71,6 +71,10 @@ fn setup(
             button_orbit: MouseButton::Middle,
             button_pan: MouseButton::Middle,
             modifier_pan: Some(KeyCode::ShiftLeft),
+            // Also enable zooming by holding right click and moving the mouse
+            button_zoom: Some(MouseButton::Right),
+            // Optionally configure button zoom to use left-right mouse movement
+            // button_zoom_axis: ButtonZoomAxis::X,
             // Reverse the zoom direction
             reversed_zoom: true,
             // Use alternate touch controls

src/input.rs

@@ -2,7 +2,7 @@ use bevy::input::gestures::PinchGesture;
 use bevy::input::mouse::{MouseMotion, MouseScrollUnit, MouseWheel};
 use bevy::prelude::*;
 
-use crate::{ActiveCameraData, PanOrbitCamera, TrackpadBehavior};
+use crate::{ActiveCameraData, ButtonZoomAxis, PanOrbitCamera, TrackpadBehavior};
 
 #[derive(Resource, Default, Debug)]
 pub struct MouseKeyTracker {
@@ -52,6 +52,18 @@ pub fn mouse_key_tracker(
     // Process pinch events
     let pinch_zoom = process_pinch_events(&mut pinch_events, pan_orbit, &key_input);
 
+    // If zoom button set, apply zoom based on mouse movement
+    let mouse_zoom = if button_zoom_pressed(pan_orbit, &mouse_input) {
+        let delta = match pan_orbit.button_zoom_axis {
+            ButtonZoomAxis::X => mouse_delta.x,
+            ButtonZoomAxis::Y => -mouse_delta.y,
+            ButtonZoomAxis::XY => mouse_delta.x + -mouse_delta.y,
+        };
+        delta * 0.03
+    } else {
+        0.0
+    };
+
     // Handle mouse movement for orbiting and panning
     if orbit_pressed(pan_orbit, &mouse_input, &key_input) {
         orbit += mouse_delta;
@@ -67,7 +79,7 @@ pub fn mouse_key_tracker(
     camera_movement.orbit = orbit;
     camera_movement.pan = pan;
     camera_movement.scroll_line = scroll_result.scroll_line;
-    camera_movement.scroll_pixel = scroll_result.scroll_pixel + pinch_zoom;
+    camera_movement.scroll_pixel = scroll_result.scroll_pixel + pinch_zoom + mouse_zoom;
     camera_movement.orbit_button_changed = orbit_button_changed;
 }
 
@@ -264,3 +276,21 @@ pub fn pan_just_pressed(
             .modifier_orbit
             .is_none_or(|modifier| !key_input.pressed(modifier))
 }
+
+pub fn button_zoom_pressed(
+    pan_orbit: &PanOrbitCamera,
+    mouse_input: &Res<ButtonInput<MouseButton>>,
+) -> bool {
+    pan_orbit
+        .button_zoom
+        .is_some_and(|btn| mouse_input.pressed(btn))
+}
+
+pub fn button_zoom_just_pressed(
+    pan_orbit: &PanOrbitCamera,
+    mouse_input: &Res<ButtonInput<MouseButton>>,
+) -> bool {
+    pan_orbit
+        .button_zoom
+        .is_some_and(|btn| mouse_input.just_pressed(btn))
+}

src/lib.rs

@@ -14,7 +14,7 @@ use bevy_egui::EguiPreUpdateSet;
 
 #[cfg(feature = "bevy_egui")]
 pub use crate::egui::{EguiFocusIncludesHover, EguiWantsFocus};
-use crate::input::{mouse_key_tracker, MouseKeyTracker};
+use crate::input::{button_zoom_just_pressed, mouse_key_tracker, MouseKeyTracker};
 pub use crate::touch::TouchControls;
 use crate::touch::{touch_tracker, TouchGestures, TouchTracker};
 use crate::traits::OptionalClamp;
@@ -217,6 +217,12 @@ pub struct PanOrbitCamera {
     /// Button used to pan the camera.
     /// Defaults to `Button::Right`.
     pub button_pan: MouseButton,
+    /// Button used to zoom the camera, by holding it down and moving the mouse forward and back.
+    /// Defaults to `None`.
+    pub button_zoom: Option<MouseButton>,
+    /// Which axis should zoom the camera when using `button_zoom`.
+    /// Defaults to `ButtonZoomAxis::Y`.
+    pub button_zoom_axis: ButtonZoomAxis,
     /// Key that must be pressed for `button_orbit` to work.
     /// Defaults to `None` (no modifier).
     pub modifier_orbit: Option<KeyCode>,
@@ -293,6 +299,8 @@ impl Default for PanOrbitCamera {
             zoom_smoothness: 0.1,
             button_orbit: MouseButton::Left,
             button_pan: MouseButton::Right,
+            button_zoom: None,
+            button_zoom_axis: ButtonZoomAxis::Y,
             modifier_orbit: None,
             modifier_pan: None,
             touch_enabled: true,
@@ -357,6 +365,17 @@ pub enum FocusBoundsShape {
     Cuboid(Cuboid),
 }
 
+/// The shape to restrict the camera's focus inside.
+#[derive(Clone, PartialEq, Debug, Reflect, Copy)]
+pub enum ButtonZoomAxis {
+    /// Zoom by moving the mouse along the x-axis.
+    X,
+    /// Zoom by moving the mouse along the y-axis.
+    Y,
+    /// Zoom by moving the mouse along either the x-axis or the y-axis.
+    XY,
+}
+
 impl From<Sphere> for FocusBoundsShape {
     fn from(value: Sphere) -> Self {
         Self::Sphere(value)
@@ -420,6 +439,7 @@ fn active_viewport_data(
             || input::pan_just_pressed(pan_orbit, &mouse_input, &key_input)
             || !pinch_events.is_empty()
             || !scroll_events.is_empty()
+            || button_zoom_just_pressed(pan_orbit, &mouse_input)
             || (touches.iter_just_pressed().count() > 0
                 && touches.iter_just_pressed().count() == touches.iter().count());