opaque.rs

use bevy_reflect::{prelude::ReflectDefault, Reflect};

/// Render method used for opaque materials.
///
/// The forward rendering main pass draws each mesh entity and shades it according to its
/// corresponding material and the lights that affect it. Some render features like Screen Space
/// Ambient Occlusion require running depth and normal prepasses, that are 'deferred'-like
/// prepasses over all mesh entities to populate depth and normal textures. This means that when
/// using render features that require running prepasses, multiple passes over all visible geometry
/// are required. This can be slow if there is a lot of geometry that cannot be batched into few
/// draws.
///
/// Deferred rendering runs a prepass to gather not only geometric information like depth and
/// normals, but also all the material properties like base color, emissive color, reflectance,
/// metalness, etc, and writes them into a deferred 'g-buffer' texture. The deferred main pass is
/// then a fullscreen pass that reads data from these textures and executes shading. This allows
/// for one pass over geometry, but is at the cost of not being able to use MSAA, and has heavier
/// bandwidth usage which can be unsuitable for low end mobile or other bandwidth-constrained devices.
///
/// If a material indicates `OpaqueRendererMethod::Auto`, `DefaultOpaqueRendererMethod` will be used.
#[derive(Default, Clone, Copy, Debug, PartialEq, Reflect)]
#[reflect(Default, Clone, PartialEq)]
pub enum OpaqueRendererMethod {
    #[default]
    Forward,
    Deferred,
    Auto,
}