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Add example to demonstrate manual generation and UV mapping of 3D mesh (generate_custom_mesh) solve #4922 (#8909)

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# Objective

- Fixes #4922

## Solution

- Add an example that maps a custom texture on a 3D mesh.

---

## Changelog

> Added the texture itself (confirmed with mod on discord before it
should be ok) to the assets folder, added to the README and Cargo.toml.

---------

Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Sélène Amanita <134181069+Selene-Amanita@users.noreply.github.com>
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Adam Kobzan 2023-06-23 22:26:37 +03:00 committed by GitHub
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10
Cargo.toml
View file

@ -447,6 +447,16 @@ description = "A scene showcasing the built-in 3D shapes"
category = "3D Rendering"
wasm = true
[[example]]
name = "generate_custom_mesh"
path = "examples/3d/generate_custom_mesh.rs"
[package.metadata.example.generate_custom_mesh]
name = "Generate Custom Mesh"
description = "Simple showcase of how to generate a custom mesh with a custom texture"
category = "3D Rendering"
wasm = true
[[example]]
name = "anti_aliasing"
path = "examples/3d/anti_aliasing.rs"

268
examples/3d/generate_custom_mesh.rs Normal file
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@ -0,0 +1,268 @@
// ! This example demonstrates how to create a custom mesh,
// ! assign a custom UV mapping for a custom texture,
// ! and how to change the UV mapping at run-time.
use bevy::prelude::*;
use bevy::render::mesh::Indices;
use bevy::render::mesh::VertexAttributeValues;
use bevy::render::render_resource::PrimitiveTopology;
// Define a "marker" component to mark the custom mesh. Marker components are often used in Bevy for
// filtering entities in queries with With, they're usually not queried directly since they don't contain information within them.
#[derive(Component)]
struct CustomUV;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, input_handler)
.run();
}
fn setup(
mut commands: Commands,
asset_server: ResMut<AssetServer>,
mut materials: ResMut<Assets<StandardMaterial>>,
mut meshes: ResMut<Assets<Mesh>>,
) {
// Import the custom texture.
let custom_texture_handle: Handle<Image> = asset_server.load("textures/array_texture.png");
// Create and save a handle to the mesh.
let cube_mesh_handle: Handle<Mesh> = meshes.add(create_cube_mesh());
// Render the mesh with the custom texture using a PbrBundle, add the marker.
commands.spawn((
PbrBundle {
mesh: cube_mesh_handle,
material: materials.add(StandardMaterial {
base_color_texture: Some(custom_texture_handle),
..default()
}),
..default()
},
CustomUV,
));
// Transform for the camera and lighting, looking at (0,0,0) (the position of the mesh).
let camera_and_light_transform =
Transform::from_xyz(1.8, 1.8, 1.8).looking_at(Vec3::ZERO, Vec3::Y);
// Camera in 3D space.
commands.spawn(Camera3dBundle {
transform: camera_and_light_transform,
..default()
});
// Light up the scene.
commands.spawn(PointLightBundle {
point_light: PointLight {
intensity: 1000.0,
range: 100.0,
..default()
},
transform: camera_and_light_transform,
..default()
});
// Text to describe the controls.
commands.spawn(
TextBundle::from_section(
"Controls:\nSpace: Change UVs\nX/Y/Z: Rotate\nR: Reset orientation",
TextStyle {
font_size: 20.0,
..default()
},
)
.with_style(Style {
position_type: PositionType::Absolute,
top: Val::Px(12.0),
left: Val::Px(12.0),
..default()
}),
);
}
// System to receive input from the user,
// check out examples/input/ for more examples about user input.
fn input_handler(
keyboard_input: Res<Input<KeyCode>>,
mesh_query: Query<&Handle<Mesh>, With<CustomUV>>,
mut meshes: ResMut<Assets<Mesh>>,
mut query: Query<&mut Transform, With<CustomUV>>,
time: Res<Time>,
) {
if keyboard_input.just_pressed(KeyCode::Space) {
let mesh_handle = mesh_query.get_single().expect("Query not successful");
let mesh = meshes.get_mut(mesh_handle).unwrap();
toggle_texture(mesh);
}
if keyboard_input.pressed(KeyCode::X) {
for mut transform in &mut query {
transform.rotate_x(time.delta_seconds() / 1.2);
}
}
if keyboard_input.pressed(KeyCode::Y) {
for mut transform in &mut query {
transform.rotate_y(time.delta_seconds() / 1.2);
}
}
if keyboard_input.pressed(KeyCode::Z) {
for mut transform in &mut query {
transform.rotate_z(time.delta_seconds() / 1.2);
}
}
if keyboard_input.pressed(KeyCode::R) {
for mut transform in &mut query {
transform.look_to(Vec3::NEG_Z, Vec3::Y);
}
}
}
fn create_cube_mesh() -> Mesh {
let mut cube_mesh = Mesh::new(PrimitiveTopology::TriangleList);
#[rustfmt::skip]
cube_mesh.insert_attribute(
Mesh::ATTRIBUTE_POSITION,
// Each array is an [x, y, z] coordinate in local space.
// Meshes always rotate around their local [0, 0, 0] when a rotation is applied to their Transform.
// By centering our mesh around the origin, rotating the mesh preserves its center of mass.
vec![
// top (facing towards +y)
[-0.5, 0.5, -0.5], // vertex with index 0
[0.5, 0.5, -0.5], // vertex with index 1
[0.5, 0.5, 0.5], // etc. until 23
[-0.5, 0.5, 0.5],
// bottom (-y)
[-0.5, -0.5, -0.5],
[0.5, -0.5, -0.5],
[0.5, -0.5, 0.5],
[-0.5, -0.5, 0.5],
// right (+x)
[0.5, -0.5, -0.5],
[0.5, -0.5, 0.5],
[0.5, 0.5, 0.5], // This vertex is at the same position as vertex with index 2, but they'll have different UV and normal
[0.5, 0.5, -0.5],
// left (-x)
[-0.5, -0.5, -0.5],
[-0.5, -0.5, 0.5],
[-0.5, 0.5, 0.5],
[-0.5, 0.5, -0.5],
// back (+z)
[-0.5, -0.5, 0.5],
[-0.5, 0.5, 0.5],
[0.5, 0.5, 0.5],
[0.5, -0.5, 0.5],
// forward (-z)
[-0.5, -0.5, -0.5],
[-0.5, 0.5, -0.5],
[0.5, 0.5, -0.5],
[0.5, -0.5, -0.5],
],
);
// Set-up UV coordinated to point to the upper (V < 0.5), "dirt+grass" part of the texture.
// Take a look at the custom image (assets/textures/array_texture.png)
// so the UV coords will make more sense
// Note: (0.0, 0.0) = Top-Left in UV mapping, (1.0, 1.0) = Bottom-Right in UV mapping
#[rustfmt::skip]
cube_mesh.insert_attribute(
Mesh::ATTRIBUTE_UV_0,
vec![
// Assigning the UV coords for the top side.
[0.0, 0.2], [0.0, 0.0], [1.0, 0.0], [1.0, 0.25],
// Assigning the UV coords for the bottom side.
[0.0, 0.45], [0.0, 0.25], [1.0, 0.25], [1.0, 0.45],
// Assigning the UV coords for the right side.
[1.0, 0.45], [0.0, 0.45], [0.0, 0.2], [1.0, 0.2],
// Assigning the UV coords for the left side.
[1.0, 0.45], [0.0, 0.45], [0.0, 0.2], [1.0, 0.2],
// Assigning the UV coords for the back side.
[0.0, 0.45], [0.0, 0.2], [1.0, 0.2], [1.0, 0.45],
// Assigning the UV coords for the forward side.
[0.0, 0.45], [0.0, 0.2], [1.0, 0.2], [1.0, 0.45],
],
);
// For meshes with flat shading, normals are orthogonal (pointing out) from the direction of
// the surface.
// Normals are required for correct lighting calculations.
// Each array represents a normalized vector, which length should be equal to 1.0.
#[rustfmt::skip]
cube_mesh.insert_attribute(
Mesh::ATTRIBUTE_NORMAL,
vec![
// Normals for the top side (towards +y)
[0.0, 1.0, 0.0],
[0.0, 1.0, 0.0],
[0.0, 1.0, 0.0],
[0.0, 1.0, 0.0],
// Normals for the bottom side (towards -y)
[0.0, -1.0, 0.0],
[0.0, -1.0, 0.0],
[0.0, -1.0, 0.0],
[0.0, -1.0, 0.0],
// Normals for the right side (towards +x)
[1.0, 0.0, 0.0],
[1.0, 0.0, 0.0],
[1.0, 0.0, 0.0],
[1.0, 0.0, 0.0],
// Normals for the left side (towards -x)
[-1.0, 0.0, 0.0],
[-1.0, 0.0, 0.0],
[-1.0, 0.0, 0.0],
[-1.0, 0.0, 0.0],
// Normals for the back side (towards +z)
[0.0, 0.0, 1.0],
[0.0, 0.0, 1.0],
[0.0, 0.0, 1.0],
[0.0, 0.0, 1.0],
// Normals for the forward side (towards -z)
[0.0, 0.0, -1.0],
[0.0, 0.0, -1.0],
[0.0, 0.0, -1.0],
[0.0, 0.0, -1.0],
],
);
// Create the triangles out of the 24 vertices we created.
// To construct a square, we need 2 triangles, therefore 12 triangles in total.
// To construct a triangle, we need the indices of its 3 defined vertices, adding them one
// by one, in a counter-clockwise order (relative to the position of the viewer, the order
// should appear counter-clockwise from the front of the triangle, in this case from outside the cube).
// Read more about how to correctly build a mesh manually in the Bevy documentation of a Mesh,
// further examples and the implementation of the built-in shapes.
#[rustfmt::skip]
cube_mesh.set_indices(Some(Indices::U32(vec![
0,3,1 , 1,3,2, // triangles making up the top (+y) facing side.
4,5,7 , 5,6,7, // bottom (-y)
8,11,9 , 9,11,10, // right (+x)
12,13,15 , 13,14,15, // left (-x)
16,19,17 , 17,19,18, // back (+z)
20,21,23 , 21,22,23, // forward (-z)
])));
cube_mesh
}
// Function that changes the UV mapping of the mesh, to apply the other texture.
fn toggle_texture(mesh_to_change: &mut Mesh) {
// Get a mutable reference to the values of the UV attribute, so we can iterate over it.
let uv_attribute = mesh_to_change.attribute_mut(Mesh::ATTRIBUTE_UV_0).unwrap();
// The format of the UV coordinates should be Float32x2.
let VertexAttributeValues::Float32x2(uv_attribute) = uv_attribute else {
panic!("Unexpected vertex format, expected Float32x2.");
};
// Iterate over the UV coordinates, and change them as we want.
for uv_coord in uv_attribute.iter_mut() {
// If the UV coordinate points to the upper, "dirt+grass" part of the texture...
if (uv_coord[1] + 0.5) < 1.0 {
// ... point to the equivalent lower, "sand+water" part instead,
uv_coord[1] += 0.5;
} else {
// else, point back to the upper, "dirt+grass" part.
uv_coord[1] -= 0.5;
}
}
}

1
examples/README.md
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@ -120,6 +120,7 @@ Example | Description
[Atmospheric Fog](../examples/3d/atmospheric_fog.rs) | A scene showcasing the atmospheric fog effect
[Blend Modes](../examples/3d/blend_modes.rs) | Showcases different blend modes
[Fog](../examples/3d/fog.rs) | A scene showcasing the distance fog effect
[Generate Custom Mesh](../examples/3d/generate_custom_mesh.rs) | Simple showcase of how to generate a custom mesh with a custom texture
[Lighting](../examples/3d/lighting.rs) | Illustrates various lighting options in a simple scene
[Lines](../examples/3d/lines.rs) | Create a custom material to draw 3d lines
[Load glTF](../examples/3d/load_gltf.rs) | Loads and renders a glTF file as a scene