Struct ScatteringMedium 

pub struct ScatteringMedium {
    pub label: Option<Cow<'static, str>>,
    pub falloff_resolution: u32,
    pub phase_resolution: u32,
    pub terms: SmallVec<[ScatteringTerm; 1]>,
}

An asset that defines how a material scatters light.

In order to calculate how light passes through a medium, you need three pieces of information:

• how much light the medium absorbs per unit length
• how much light the medium scatters per unit length
• what directions the medium is likely to scatter light in.

The first two are fairly simple, and are sometimes referred to together (accurately enough) as the medium’s optical density.

The last, defined by a phase function, is the most important in creating the look of a medium. Our brains are very good at noticing (if unconsciously) that a dust storm scatters light differently than a rain cloud, for example. See the docs on PhaseFunction for more info.

In reality, media are often composed of multiple elements that scatter light independently, for Earth’s atmosphere is composed of the gas itself, but also suspended dust and particulate. These each scatter light differently, and are distributed in different amounts at different altitudes. In a ScatteringMedium, these are each represented by a ScatteringTerm

Technical Details

A ScatteringMedium is represented on the GPU by a set of two LUTs, which are re-created every time the asset is modified. See the docs on bevy_pbr::GpuScatteringMedium for more info.

Fields

label: Option<Cow<'static, str>>

An optional label for the medium, used when creating the LUTs on the GPU.

falloff_resolution: u32

The resolution at which to sample the falloff distribution of each scattering term. Custom or more detailed distributions may benefit from a higher value, at the cost of more memory use.

phase_resolution: u32

The resolution at which to sample the phase function of each scattering term. Custom or more detailed phase functions may benefit from a higher value, at the cost of more memory use.

terms: SmallVec<[ScatteringTerm; 1]>

The list of ScatteringTerms that compose this ScatteringMedium

Implementations

impl ScatteringMedium

pub fn new( falloff_resolution: u32, phase_resolution: u32, terms: impl IntoIterator<Item = ScatteringTerm>, ) -> ScatteringMedium

Returns a scattering medium with a default label and the specified scattering terms.

pub fn with_label(self, label: impl Into<Cow<'static, str>>) -> ScatteringMedium

Consumes and returns this scattering medium with a new label.

pub fn with_density_multiplier(self, multiplier: f32) -> ScatteringMedium

Consumes and returns this scattering medium with each scattering terms’ densities multiplied by multiplier.

pub fn earth(falloff_resolution: u32, phase_resolution: u32) -> ScatteringMedium

Returns a scattering medium representing an earth atmosphere.

Uses physically-based scale heights from Earth’s atmosphere, assuming a 60 km atmosphere height:

• Rayleigh (molecular) scattering: 8 km scale height
• Mie (aerosol) scattering: 1.2 km scale height

pub fn mars( falloff_resolution: u32, phase_resolution: u32, dust_phase: Handle<Image>, ) -> ScatteringMedium

Returns a scattering medium representing a Martian atmosphere Schneegans et al. 2024.

Constituents:

• Rayleigh: carbon dioxide
• Dust: wavelength-dependent Mie phase, double-exponential density

Requires an Nx1 chromatic phase texture for the dust term.

Trait Implementations

impl Asset for ScatteringMedium

impl Clone for ScatteringMedium

fn clone(&self) -> ScatteringMedium

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Default for ScatteringMedium

fn default() -> ScatteringMedium

Returns the “default value” for a type.

impl TypePath for ScatteringMedium

fn type_path() -> &'static str

Returns the fully qualified path of the underlying type.

fn short_type_path() -> &'static str

Returns a short, pretty-print enabled path to the type.

fn type_ident() -> Option<&'static str>

Returns the name of the type, or None if it is anonymous.

fn crate_name() -> Option<&'static str>

Returns the name of the crate the type is in, or None if it is anonymous.

fn module_path() -> Option<&'static str>

Returns the path to the module the type is in, or None if it is anonymous.

impl VisitAssetDependencies for ScatteringMedium

fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId))