add flat color and normal interpolation to standard material

crates/bevy_pbr/src/interpolation.rs

@@ -0,0 +1,9 @@
+use bevy_reflect::{std_traits::ReflectDefault, Reflect};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Default, Reflect)]
+#[reflect(Default, Clone, PartialEq)]
+pub enum InterpolationMethod {
+    #[default]
+    Linear,
+    Flat,
+}

crates/bevy_pbr/src/lib.rs

@@ -31,6 +31,7 @@ pub mod decal;
 pub mod deferred;
 mod extended_material;
 mod fog;
+mod interpolation;
 mod light_probe;
 mod lightmap;
 mod material;
@@ -60,6 +61,7 @@ pub use components::*;
 pub use decal::clustered::ClusteredDecalPlugin;
 pub use extended_material::*;
 pub use fog::*;
+pub use interpolation::*;
 pub use light_probe::*;
 pub use lightmap::*;
 pub use material::*;

crates/bevy_pbr/src/pbr_material.rs

@@ -769,6 +769,8 @@ pub struct StandardMaterial {
 
     /// The transform applied to the UVs corresponding to `ATTRIBUTE_UV_0` on the mesh before sampling. Default is identity.
     pub uv_transform: Affine2,
+
+    pub interpolation_method: InterpolationMethod,
 }
 
 impl StandardMaterial {
@@ -924,6 +926,7 @@ impl Default for StandardMaterial {
             opaque_render_method: OpaqueRendererMethod::Auto,
             deferred_lighting_pass_id: DEFAULT_PBR_DEFERRED_LIGHTING_PASS_ID,
             uv_transform: Affine2::IDENTITY,
+            interpolation_method: InterpolationMethod::Linear,
         }
     }
 }
@@ -1228,6 +1231,7 @@ bitflags! {
         const CLEARCOAT_NORMAL_UV      = 0x100000;
         const SPECULAR_UV              = 0x200000;
         const SPECULAR_TINT_UV         = 0x400000;
+        const FLAT_INTERPOLATION       = 0x800000;
         const DEPTH_BIAS               = 0xffffffff_00000000;
     }
 }
@@ -1352,11 +1356,17 @@ impl From<&StandardMaterial> for StandardMaterialKey {
             );
         }
 
+        key.set(
+            StandardMaterialKey::FLAT_INTERPOLATION,
+            material.interpolation_method == InterpolationMethod::Flat,
+        );
+
         key.insert(StandardMaterialKey::from_bits_retain(
             // Casting to i32 first to ensure the full i32 range is preserved.
             // (wgpu expects the depth_bias as an i32 when this is extracted in a later step)
             (material.depth_bias as i32 as u64) << STANDARD_MATERIAL_KEY_DEPTH_BIAS_SHIFT,
         ));
+
         key
     }
 }
@@ -1517,6 +1527,10 @@ impl Material for StandardMaterial {
                     StandardMaterialKey::SPECULAR_TINT_UV,
                     "STANDARD_MATERIAL_SPECULAR_TINT_UV_B",
                 ),
+                (
+                    StandardMaterialKey::FLAT_INTERPOLATION,
+                    "STANDARD_MATERIAL_FLAT_INTERPOLATION",
+                ),
             ] {
                 if key.bind_group_data.intersects(flags) {
                     shader_defs.push(shader_def.into());

crates/bevy_pbr/src/render/forward_io.wgsl

@@ -34,7 +34,11 @@ struct VertexOutput {
     // and `frag coord` when used as a fragment stage input
     @builtin(position) position: vec4<f32>,
     @location(0) world_position: vec4<f32>,
+#ifdef STANDARD_MATERIAL_FLAT_INTERPOLATION
+    @location(1) @interpolate(flat) world_normal: vec3<f32>,
+#else
     @location(1) world_normal: vec3<f32>,
+#endif
 #ifdef VERTEX_UVS_A
     @location(2) uv: vec2<f32>,
 #endif
@@ -45,8 +49,12 @@ struct VertexOutput {
     @location(4) world_tangent: vec4<f32>,
 #endif
 #ifdef VERTEX_COLORS
+#ifdef STANDARD_MATERIAL_FLAT_INTERPOLATION
+    @location(5) @interpolate(flat) color: vec4<f32>,
+#else
     @location(5) color: vec4<f32>,
 #endif
+#endif
 #ifdef VERTEX_OUTPUT_INSTANCE_INDEX
     @location(6) @interpolate(flat) instance_index: u32,
 #endif

rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly"