z-fighting test for depth bias

Cargo.toml

[package]
name = "depth_bias_test"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
bevy = "0.9"

main.rs

use std::f32::consts::PI;

use bevy::{
    prelude::*,
    render::mesh::shape::Cube,
    window::close_on_esc,
};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_startup_system(setup)
        .add_system(oscillate)
        .add_system(close_on_esc)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let red = materials.add(StandardMaterial {
        base_color: Color::RED,
        depth_bias: 0.0,
        ..default()
    });

    let cyan = materials.add(StandardMaterial {
        base_color: Color::CYAN,
        depth_bias: 1.0,
        ..default()
    });

    commands
        .spawn(PbrBundle {
            mesh: meshes.add(Cube::new(1.0).into()),
            material: red,
            ..default()
        });

    commands
        .spawn(PbrBundle {
            mesh: meshes.add(Cube::new(1.0).into()),
            material: cyan,
            transform: Transform::from_xyz(0.2, 0.0, 0.0),
            ..default()
        });

    commands
        .spawn(PointLightBundle {
            point_light: PointLight {
                intensity: 1500.0,
                ..default()
            },
            transform: Transform::from_xyz(4.0, 4.0, 8.0),
            ..default()
        });

    commands
        .spawn(SpatialBundle::default())
        .insert(Oscillate {
            lower: -PI * 30.0 / 180.0,
            upper: PI * 30.0 / 180.0,
            rate: 3.0 / (2.0 * PI),
            axis: Vec3::X,
        })
        .with_children(|p| {
            p.spawn(Camera3dBundle {
                transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Z),
                ..default()
            });
        });
}

#[derive(Component)]
struct Oscillate {
    lower: f32,
    upper: f32,
    rate: f32,
    axis: Vec3,
}

fn oscillate(
    mut oscillating: Query<(&mut Transform, &Oscillate)>,
    time: Res<Time>,
) {
    for (mut tf, osc) in &mut oscillating {
        let angle = (osc.upper - osc.lower) * (osc.rate * time.elapsed_seconds()).cos() + osc.lower;
        tf.rotation = Quat::from_axis_angle(osc.axis, angle);
    }
}