Merge #224

224: Fix rapier debug render r=zicklag a=zicklag

Fixes #132.

Found out that #132 was caused by the fact that the debug lines plugin that rapier uses to manage debug rendering requires that 4 entities be kept alive to contain the debug lines.

The issue is when we try to reset the world by deleting all entities other than the camera, those entities get deleted, too. And we can't filter those entities out because their distinguishing component is private. Also, there isn't a way to re-create those entities after adding the plugin.

This works around the issue by implementing a custom debug lines renderer for Rapier that uses Egui to draw the lines instead.

It's simple and mostly copied from rapier's plugin.

Co-authored-by: Zicklag <zicklag@katharostech.com>

src/main.rs

@@ -112,7 +112,7 @@ fn main() {
         .add_plugin(PlatformPlugin)
         .add_plugin(LocalizationPlugin)
         .add_plugin(LoadingPlugin)
-        .add_plugin(RapierPhysicsPlugin::<NoUserData>::pixels_per_meter(100.0))
+        .add_plugin(RapierPhysicsPlugin::<NoUserData>::default())
         .add_plugin(InputManagerPlugin::<PlayerAction>::default())
         .add_plugin(InputManagerPlugin::<MenuAction>::default())
         .add_plugin(AttackPlugin)
@@ -139,17 +139,16 @@ fn main() {
 
     // Add debug plugins if enabled
     if engine_config.debug_tools {
-        app.add_plugin(RapierDebugRenderPlugin::default())
-            .insert_resource(DebugRenderContext {
-                enabled: false,
-                ..default()
-            })
-            .add_plugin(InspectableRapierPlugin)
-            .insert_resource(WorldInspectorParams {
-                enabled: false,
-                ..default()
-            })
-            .add_plugin(WorldInspectorPlugin::new());
+        app.insert_resource(DebugRenderContext {
+            enabled: false,
+            ..default()
+        })
+        .add_plugin(InspectableRapierPlugin)
+        .insert_resource(WorldInspectorParams {
+            enabled: false,
+            ..default()
+        })
+        .add_plugin(WorldInspectorPlugin::new());
     }
 
     // Register assets and loaders

src/ui.rs

@@ -53,7 +53,8 @@ impl Plugin for UIPlugin {
             );
 
         if ENGINE_CONFIG.debug_tools {
-            app.add_system(debug_tools::debug_tools_window);
+            app.add_system(debug_tools::debug_tools_window)
+                .add_system_to_stage(CoreStage::Last, debug_tools::rapier_debug_render);
         }
     }
 }

src/ui/debug_tools.rs

@@ -2,7 +2,14 @@ use bevy::prelude::*;
 use bevy_egui::*;
 use bevy_fluent::Localization;
 use bevy_inspector_egui::WorldInspectorParams;
-use bevy_rapier2d::prelude::DebugRenderContext;
+use bevy_rapier2d::{
+    plugin::RapierContext,
+    prelude::{ColliderDebugColor, DebugRenderContext},
+    rapier::{
+        math::{Point, Real},
+        prelude::{DebugRenderBackend, DebugRenderObject},
+    },
+};
 
 use crate::localization::LocalizationExt;
 
@@ -17,11 +24,20 @@ pub fn debug_tools_window(
 ) {
     let ctx = egui_context.ctx_mut();
 
-    // Toggle window visibility
+    // Toggle debug window visibility
     if input.just_pressed(KeyCode::F12) {
         *visible = !*visible;
     }
 
+    // Shortcut to toggle collision shapes without having to use the menu
+    if input.just_pressed(KeyCode::F10) {
+        rapier_debug.enabled = !rapier_debug.enabled;
+    }
+    // Shortcut to toggle the inspector without having to use the menu
+    if input.just_pressed(KeyCode::F9) {
+        inspector.enabled = !inspector.enabled;
+    }
+
     // Display debug tool window
     egui::Window::new(localization.get("debug-tools"))
         // ID is needed because title comes from localizaition which can change
@@ -31,13 +47,119 @@ pub fn debug_tools_window(
             // Show collision shapes
             ui.checkbox(
                 &mut rapier_debug.enabled,
-                localization.get("show-collision-shapes"),
+                format!("{} ( F10 )", localization.get("show-collision-shapes")),
             );
 
             // Show world inspector
             ui.checkbox(
                 &mut inspector.enabled,
-                localization.get("show-world-inspector"),
+                format!("{} ( F9 )", localization.get("show-world-inspector")),
+            );
+        });
+}
+
+/// Renders the rapier debug display
+pub fn rapier_debug_render(
+    rapier_context: Res<RapierContext>,
+    mut egui_context: ResMut<EguiContext>,
+    mut rapier_debug: ResMut<DebugRenderContext>,
+    camera: Query<(&Camera, &GlobalTransform)>,
+    custom_colors: Query<&ColliderDebugColor>,
+) {
+    if !rapier_debug.enabled {
+        return;
+    }
+    let (camera, camera_transform) = camera.single();
+
+    // Create a frameless panel to allow us to render over anywhere on the screen
+    egui::CentralPanel::default()
+        .frame(egui::Frame::none())
+        .show(egui_context.ctx_mut(), |ui| {
+            let painter = ui.painter();
+
+            let mut backend = RapierEguiRenderBackend {
+                egui_size: ui.available_size(),
+                camera,
+                camera_transform,
+                custom_colors,
+                context: &rapier_context,
+                painter,
+            };
+
+            rapier_debug.pipeline.render(
+                &mut backend,
+                &rapier_context.bodies,
+                &rapier_context.colliders,
+                &rapier_context.impulse_joints,
+                &rapier_context.multibody_joints,
+                &rapier_context.narrow_phase,
             );
         });
 }
+
+/// Rapier debug rendering backend that uses Egui to draw the lines
+struct RapierEguiRenderBackend<'world, 'state, 'a, 'b, 'c> {
+    egui_size: egui::Vec2,
+    custom_colors: Query<'world, 'state, &'a ColliderDebugColor>,
+    context: &'b RapierContext,
+    camera: &'c Camera,
+    camera_transform: &'c GlobalTransform,
+    painter: &'c egui::Painter,
+}
+
+impl<'world, 'state, 'a, 'b, 'c> RapierEguiRenderBackend<'world, 'state, 'a, 'b, 'c> {
+    /// Helper to grab the objects custom collider color if it exists
+    fn object_color(&self, object: DebugRenderObject, default: [f32; 4]) -> egui::Color32 {
+        let color = match object {
+            DebugRenderObject::Collider(h, ..) => self.context.colliders.get(h).and_then(|co| {
+                self.custom_colors
+                    .get(Entity::from_bits(co.user_data as u64))
+                    .map(|co| co.0)
+                    .ok()
+            }),
+            _ => None,
+        };
+
+        let color = color.map(|co| co.as_hsla_f32()).unwrap_or(default);
+
+        egui::Rgba::from_rgba_premultiplied(color[0], color[1], color[2], color[3]).into()
+    }
+}
+
+impl<'world, 'state, 'a, 'b, 'c> DebugRenderBackend
+    for RapierEguiRenderBackend<'world, 'state, 'a, 'b, 'c>
+{
+    /// Draw a debug line
+    fn draw_line(
+        &mut self,
+        object: DebugRenderObject,
+        a: Point<Real>,
+        b: Point<Real>,
+        color: [f32; 4],
+    ) {
+        // Convert world coordinates to normalized device coordinates
+        let a = self
+            .camera
+            .world_to_ndc(self.camera_transform, Vec3::new(a[0], a[1], 0.0));
+        let b = self
+            .camera
+            .world_to_ndc(self.camera_transform, Vec3::new(b[0], b[1], 0.0));
+
+        if let (Some(a), Some(b)) = (a, b) {
+            // Invert y and convert to egui vec2
+            let a = egui::Vec2::new(a.x, -a.y);
+            let b = egui::Vec2::new(b.x, -b.y);
+
+            // Map NDC coordinates to egui points
+            let half_size = self.egui_size / 2.0;
+            let a = a * half_size + half_size;
+            let b = b * half_size + half_size;
+
+            // Paint the line
+            self.painter.line_segment(
+                [a.to_pos2(), b.to_pos2()],
+                (1.0, self.object_color(object, color)),
+            )
+        }
+    }
+}