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lines.rs
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lines.rs
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//! Create a custom material to draw basic lines in 3D
use bevy::{
pbr::{MaterialPipeline, MaterialPipelineKey},
prelude::*,
reflect::TypePath,
render::{
mesh::{MeshVertexBufferLayout, PrimitiveTopology},
render_asset::RenderAssetUsages,
render_resource::{
AsBindGroup, PolygonMode, RenderPipelineDescriptor, ShaderRef,
SpecializedMeshPipelineError,
},
},
};
fn main() {
App::new()
.add_plugins((DefaultPlugins, MaterialPlugin::<LineMaterial>::default()))
.add_systems(Startup, setup)
.run();
}
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<LineMaterial>>,
) {
// Spawn a list of lines with start and end points for each lines
commands.spawn(MaterialMeshBundle {
mesh: meshes.add(LineList {
lines: vec![
(Vec3::ZERO, Vec3::new(1.0, 1.0, 0.0)),
(Vec3::new(1.0, 1.0, 0.0), Vec3::new(1.0, 0.0, 0.0)),
],
}),
transform: Transform::from_xyz(-1.5, 0.0, 0.0),
material: materials.add(LineMaterial {
color: Color::GREEN,
}),
..default()
});
// Spawn a line strip that goes from point to point
commands.spawn(MaterialMeshBundle {
mesh: meshes.add(LineStrip {
points: vec![
Vec3::ZERO,
Vec3::new(1.0, 1.0, 0.0),
Vec3::new(1.0, 0.0, 0.0),
],
}),
transform: Transform::from_xyz(0.5, 0.0, 0.0),
material: materials.add(LineMaterial { color: Color::BLUE }),
..default()
});
// camera
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
}
#[derive(Asset, TypePath, Default, AsBindGroup, Debug, Clone)]
struct LineMaterial {
#[uniform(0)]
color: Color,
}
impl Material for LineMaterial {
fn fragment_shader() -> ShaderRef {
"shaders/line_material.wgsl".into()
}
fn specialize(
_pipeline: &MaterialPipeline<Self>,
descriptor: &mut RenderPipelineDescriptor,
_layout: &MeshVertexBufferLayout,
_key: MaterialPipelineKey<Self>,
) -> Result<(), SpecializedMeshPipelineError> {
// This is the important part to tell bevy to render this material as a line between vertices
descriptor.primitive.polygon_mode = PolygonMode::Line;
Ok(())
}
}
/// A list of lines with a start and end position
#[derive(Debug, Clone)]
struct LineList {
lines: Vec<(Vec3, Vec3)>,
}
impl From<LineList> for Mesh {
fn from(line: LineList) -> Self {
let vertices: Vec<_> = line.lines.into_iter().flat_map(|(a, b)| [a, b]).collect();
Mesh::new(
// This tells wgpu that the positions are list of lines
// where every pair is a start and end point
PrimitiveTopology::LineList,
RenderAssetUsages::RENDER_WORLD,
)
// Add the vertices positions as an attribute
.with_inserted_attribute(Mesh::ATTRIBUTE_POSITION, vertices)
}
}
/// A list of points that will have a line drawn between each consecutive points
#[derive(Debug, Clone)]
struct LineStrip {
points: Vec<Vec3>,
}
impl From<LineStrip> for Mesh {
fn from(line: LineStrip) -> Self {
Mesh::new(
// This tells wgpu that the positions are a list of points
// where a line will be drawn between each consecutive point
PrimitiveTopology::LineStrip,
RenderAssetUsages::RENDER_WORLD,
)
// Add the point positions as an attribute
.with_inserted_attribute(Mesh::ATTRIBUTE_POSITION, line.points)
}
}