[Merged by Bors] - Change standard material defaults and update docs

crates/bevy_pbr/src/pbr_material.rs

@@ -78,22 +78,26 @@ pub struct StandardMaterial {
 
  /// Linear perceptual roughness, clamped to `[0.089, 1.0]` in the shader.
  ///
- /// Defaults to minimum of `0.089`.
+ /// Defaults to `0.5`.
  ///
  /// Low values result in a "glossy" material with specular highlights,
  /// while values close to `1` result in rough materials.
  ///
  /// If used together with a roughness/metallic texture, this is factored into the final base
  /// color as `roughness * roughness_texture_value`.
+ ///
+ /// 0.089 is the minimum floating point value that won't be rounded down to 0 in the
+ /// calculations used.
+ //
+ // Technically for 32-bit floats, 0.045 could be used.
+ // See <https://google.github.io/filament/Filament.html#materialsystem/parameterization/>
  pub perceptual_roughness: f32,
 
- /// How "metallic" the material appears, within `[0.0, 1.0]`,
- /// going from dielectric to pure metallic.
+ /// How "metallic" the material appears, within `[0.0, 1.0]`.
  ///
- /// Defaults to `0.01`.
+ /// This should be set to 0.0 or 1.0, depending on if the material is metallic or dielectric.
  ///
- /// The closer to `1` the value, the more the material will
- /// reflect light like a metal such as steel or gold.
+ /// Defaults to `0.00`.
  ///
  /// If used together with a roughness/metallic texture, this is factored into the final base
  /// color as `metallic * metallic_texture_value`.
@@ -236,19 +240,15 @@ pub struct StandardMaterial {
 impl Default for StandardMaterial {
  fn default() -> Self {
  StandardMaterial {
- base_color: Color::rgb(1.0, 1.0, 1.0),
+ // Mid-grey to approximate how bright most materials are.
+ base_color: Color::rgb(0.5, 0.5, 0.5),
  base_color_texture: None,
  emissive: Color::BLACK,
  emissive_texture: None,
- // This is the minimum the roughness is clamped to in shader code
- // See <https://google.github.io/filament/Filament.html#materialsystem/parameterization/>
- // It's the minimum floating point value that won't be rounded down to 0 in the
- // calculations used. Although technically for 32-bit floats, 0.045 could be
- // used.
- perceptual_roughness: 0.089,
- // Few materials are purely dielectric or metallic
- // This is just a default for mostly-dielectric
- metallic: 0.01,
+ // Matches Blender's default roughness.
+ perceptual_roughness: 0.5,
+ // Metallic should be set to 0.0 or 1.0.
+ metallic: 0.00,
  metallic_roughness_texture: None,
  // Minimum real-world reflectance is 2%, most materials between 2-5%
  // Expressed in a linear scale and equivalent to 4% reflectance see