add an example for creating convex shapes

examples/test_convex_shapes.rs

@@ -0,0 +1,156 @@
+mod common;
+
+use bevy::prelude::*;
+use bevy::render::mesh::Indices;
+use bevy::render::render_resource::PrimitiveTopology;
+use bevy_mod_physx::assets::GeometryInner;
+use bevy_mod_physx::physx_extras::ConvexMeshExtras;
+use bevy_mod_physx::prelude::{self as bpx, *};
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_plugins(PhysicsPlugins)
+        .add_plugins(common::DemoUtils) // optional
+        .add_systems(Startup, (
+            spawn_scene,
+            spawn_camera_and_light,
+        ))
+        .run();
+}
+
+// generates bevy mesh from physx convex mesh
+fn create_bevy_mesh_from_geometry(geometry: &Geometry) -> Mesh {
+    let mut positions = vec![];
+    let mut indices = vec![];
+    let mut normals = vec![];
+
+    match &geometry.obj {
+        GeometryInner::ConvexMesh { mesh, scale, .. } => {
+            let mesh = mesh.lock().unwrap();
+
+            let mut vertices = vec![];
+            // arbitrary axis rotation not implemented
+            assert_eq!(scale.rotation.to_bevy(), Quat::IDENTITY);
+            for vertex in mesh.get_vertices() {
+                vertices.push(vertex.to_bevy() * scale.scale.to_bevy());
+            }
+
+            let index_buffer = mesh.get_index_buffer();
+            for idx in 0..mesh.get_nb_polygons() {
+                let polygon = mesh.get_polygon_data(idx).unwrap();
+                for i in polygon.index_base+1..polygon.index_base+polygon.nb_verts-1 {
+                    let a = vertices[index_buffer[polygon.index_base as usize] as usize];
+                    let b = vertices[index_buffer[i as usize] as usize];
+                    let c = vertices[index_buffer[i as usize + 1] as usize];
+
+                    indices.push(indices.len() as u32);
+                    indices.push(indices.len() as u32);
+                    indices.push(indices.len() as u32);
+
+                    positions.push(a);
+                    positions.push(b);
+                    positions.push(c);
+
+                    let normal = (b - a).cross(c - a).normalize();
+                    normals.push(normal);
+                    normals.push(normal);
+                    normals.push(normal);
+                }
+            }
+        },
+
+        // see https://github.com/rlidwka/bevy_mod_physx/blob/2cfc2e55db7509fa881c3687800472fa73310361/src/render.rs
+        // for inspiration how to implement other shapes
+        _ => unimplemented!()
+    }
+
+    let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);
+    mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, positions);
+    mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, normals);
+    mesh.set_indices(Some(Indices::U32(indices)));
+    mesh
+}
+
+pub fn spawn_scene(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+    mut physics: ResMut<Physics>,
+    mut px_geometries: ResMut<Assets<bpx::Geometry>>,
+) {
+    // plane
+    commands.spawn((
+        RigidBody::Static,
+        bpx::Shape {
+            geometry: px_geometries.add(bpx::Geometry::halfspace(Vec3::Y)),
+            ..default()
+        },
+        PbrBundle {
+            mesh: meshes.add(shape::Plane::from_size(1000.0).into()),
+            material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
+            ..default()
+        }
+    ));
+
+    // cylinder (it's a helper for convex shape, physx doesn't have native cylinders)
+    let geometry = bpx::Geometry::cylinder(&mut physics, 0.5, 0.5, 10).unwrap();
+    let mesh = create_bevy_mesh_from_geometry(&geometry);
+    commands.spawn((
+        PbrBundle {
+            mesh: meshes.add(mesh),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(-2.0, 7.0, 0.0).with_rotation(Quat::from_rotation_z(-1.)),
+            ..default()
+        },
+        RigidBody::Dynamic,
+        bpx::Shape {
+            geometry: px_geometries.add(geometry),
+            ..default()
+        },
+    ));
+
+    // arbitrary convex shape
+    let vertices = vec![
+        Vec3::new(0., 1., 0.),
+        Vec3::new(0., -1., 0.),
+        Vec3::new(1., 0., 0.),
+        Vec3::new(-1., 0., 0.),
+        Vec3::new(0., 0., 1.),
+        Vec3::new(0., 0., -1.),
+    ];
+
+    let geometry = bpx::Geometry::convex_mesh(&mut physics, &vertices).unwrap()
+        .with_scale(Vec3::splat(0.8), Quat::IDENTITY);
+    let mesh = create_bevy_mesh_from_geometry(&geometry);
+    commands.spawn((
+        PbrBundle {
+            mesh: meshes.add(mesh),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(2.0, 7.0, 0.0).with_rotation(Quat::from_rotation_z(-1.)),
+            ..default()
+        },
+        RigidBody::Dynamic,
+        bpx::Shape {
+            geometry: px_geometries.add(geometry),
+            ..default()
+        },
+    ));
+}
+
+fn spawn_camera_and_light(mut commands: Commands) {
+    commands
+        .spawn(SpatialBundle::from_transform(Transform::from_xyz(0., 2.5, 0.)))
+        .with_children(|builder| {
+            builder.spawn(Camera3dBundle {
+                transform: Transform::from_xyz(0.0, 2.5, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
+                ..default()
+            });
+        })
+        .insert(Name::new("Camera"));
+
+    commands.spawn(DirectionalLightBundle {
+        transform: Transform::from_rotation(Quat::from_rotation_x(-std::f32::consts::FRAC_PI_4)),
+        ..default()
+    }).insert(Name::new("Light"));
+}