bevy_exponential_height_fog

Standalone Bevy extension crate that renders Unreal-style exponential height fog as a dedicated post-process pipeline.

Bevy Version

This crate requires Bevy 0.18.1 or higher.

Quick start

Add the crate and plugin:

[dependencies]
bevy_exponential_height_fog = { path = "crates/bevy_exponential_height_fog" }

use bevy::prelude::*;
use bevy_exponential_height_fog::ExponentialHeightFogPlugin;

App::new()
    .add_plugins((DefaultPlugins, ExponentialHeightFogPlugin))
    .run();

Add ExponentialHeightFog to a Camera3d:

use bevy::prelude::*;
use bevy_exponential_height_fog::{
    ExponentialHeightFog,
    ExponentialHeightFogDistanceMode,
    ExponentialHeightFogLayer,
};

commands.spawn((
    Camera3d::default(),
    Transform::from_xyz(0.0, 20.0, 20.0).looking_at(Vec3::ZERO, Vec3::Z),
    ExponentialHeightFog {
        enabled: true,
        fog_color: LinearRgba::new(0.5, 0.6, 0.7, 1.0),
        primary: ExponentialHeightFogLayer {
            enabled: true,
            density: 0.03,
            height_falloff: 0.55,
            height_offset: 0.0,
        },
        secondary: ExponentialHeightFogLayer {
            enabled: true,
            density: 0.01,
            height_falloff: 0.25,
            height_offset: 1.0,
        },
        distance_mode: ExponentialHeightFogDistanceMode::Camera,
        distance_reference_world_position: Vec3::ZERO,
        start_distance: 0.0,
        cutoff_distance: 30.0,
        distance_fade: 20.0,
        max_opacity: 0.9,
        min_density_weight: 0.0,
        min_fog_alpha: 0.001,
        sky_depth_threshold: 0.999999,
    },
));

No fog-volume entities and no shader patching are required.

Distance modes

The distance terms (start_distance, cutoff_distance, distance_fade) can be evaluated from:

• ExponentialHeightFogDistanceMode::Camera: world point to camera position.
• ExponentialHeightFogDistanceMode::SuppliedWorldCoordinates: world point to distance_reference_world_position.

For camera-target based gameplay fog, set distance_mode to SuppliedWorldCoordinates and update distance_reference_world_position every frame:

fn update_fog_reference(
    mut fog_q: Query<&mut ExponentialHeightFog, With<Camera3d>>,
    target: Res<MyCameraTargetWorldPos>,
) {
    for mut fog in &mut fog_q {
        fog.distance_mode = ExponentialHeightFogDistanceMode::SuppliedWorldCoordinates;
        fog.distance_reference_world_position = target.0;
    }
}

Features

• Separate render pipeline and render graph node (no Bevy shader overrides).
• Per-camera fog settings via ExponentialHeightFog component.
• Primary and secondary exponential height layers.
• Start/cutoff distance shaping.
• Max opacity and small-cost early-out optimization parameters.
• Automatic camera requirements:
  • DepthPrepass is required by the fog component.
  • depth texture usage is configured by the plugin.

Public API

• ExponentialHeightFogPlugin
• ExponentialHeightFog
• ExponentialHeightFogDistanceMode
• ExponentialHeightFogLayer

License

MIT License