diff --git a/crates/bevy_pbr/src/render/mesh.rs b/crates/bevy_pbr/src/render/mesh.rs index 082e20b733585..3d70cfd110eb5 100644 --- a/crates/bevy_pbr/src/render/mesh.rs +++ b/crates/bevy_pbr/src/render/mesh.rs @@ -9,7 +9,7 @@ use bevy_ecs::{ prelude::*, system::{lifetimeless::*, SystemParamItem, SystemState}, }; -use bevy_math::{Mat4, Vec2}; +use bevy_math::{Mat3A, Mat4, Vec2}; use bevy_reflect::TypeUuid; use bevy_render::{ extract_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin}, @@ -117,6 +117,9 @@ bitflags::bitflags! { #[repr(transparent)] struct MeshFlags: u32 { const SHADOW_RECEIVER = (1 << 0); + // Indicates the sign of the determinant of the 3x3 model matrix. If the sign is positive, + // then the flag should be set, else it should not be set. + const SIGN_DETERMINANT_MODEL_3X3 = (1 << 31); const NONE = 0; const UNINITIALIZED = 0xFFFF; } @@ -143,13 +146,16 @@ pub fn extract_meshes( for (entity, _, transform, handle, not_receiver, not_caster) in visible_meshes { let transform = transform.compute_matrix(); - let shadow_receiver_flags = if not_receiver.is_some() { - MeshFlags::empty().bits + let mut flags = if not_receiver.is_some() { + MeshFlags::empty() } else { - MeshFlags::SHADOW_RECEIVER.bits + MeshFlags::SHADOW_RECEIVER }; + if Mat3A::from_mat4(transform).determinant().is_sign_positive() { + flags |= MeshFlags::SIGN_DETERMINANT_MODEL_3X3; + } let uniform = MeshUniform { - flags: shadow_receiver_flags, + flags: flags.bits, transform, inverse_transpose_model: transform.inverse().transpose(), }; diff --git a/crates/bevy_pbr/src/render/mesh_functions.wgsl b/crates/bevy_pbr/src/render/mesh_functions.wgsl index 20c763bd22d79..40779b28d5c6e 100644 --- a/crates/bevy_pbr/src/render/mesh_functions.wgsl +++ b/crates/bevy_pbr/src/render/mesh_functions.wgsl @@ -17,20 +17,47 @@ fn mesh_position_local_to_clip(model: mat4x4, vertex_position: vec4) - } fn mesh_normal_local_to_world(vertex_normal: vec3) -> vec3 { - return mat3x3( - mesh.inverse_transpose_model[0].xyz, - mesh.inverse_transpose_model[1].xyz, - mesh.inverse_transpose_model[2].xyz - ) * vertex_normal; + // NOTE: The mikktspace method of normal mapping requires that the world normal is + // re-normalized in the vertex shader to match the way mikktspace bakes vertex tangents + // and normal maps so that the exact inverse process is applied when shading. Blender, Unity, + // Unreal Engine, Godot, and more all use the mikktspace method. Do not change this code + // unless you really know what you are doing. + // http://www.mikktspace.com/ + return normalize( + mat3x3( + mesh.inverse_transpose_model[0].xyz, + mesh.inverse_transpose_model[1].xyz, + mesh.inverse_transpose_model[2].xyz + ) * vertex_normal + ); +} + +// Calculates the sign of the determinant of the 3x3 model matrix based on a +// mesh flag +fn sign_determinant_model_3x3() -> f32 { + // bool(u32) is false if 0u else true + // f32(bool) is 1.0 if true else 0.0 + // * 2.0 - 1.0 remaps 0.0 or 1.0 to -1.0 or 1.0 respectively + return f32(bool(mesh.flags & MESH_FLAGS_SIGN_DETERMINANT_MODEL_3X3_BIT)) * 2.0 - 1.0; } fn mesh_tangent_local_to_world(model: mat4x4, vertex_tangent: vec4) -> vec4 { + // NOTE: The mikktspace method of normal mapping requires that the world tangent is + // re-normalized in the vertex shader to match the way mikktspace bakes vertex tangents + // and normal maps so that the exact inverse process is applied when shading. Blender, Unity, + // Unreal Engine, Godot, and more all use the mikktspace method. Do not change this code + // unless you really know what you are doing. + // http://www.mikktspace.com/ return vec4( - mat3x3( - model[0].xyz, - model[1].xyz, - model[2].xyz - ) * vertex_tangent.xyz, - vertex_tangent.w + normalize( + mat3x3( + model[0].xyz, + model[1].xyz, + model[2].xyz + ) * vertex_tangent.xyz + ), + // NOTE: Multiplying by the sign of the determinant of the 3x3 model matrix accounts for + // situations such as negative scaling. + vertex_tangent.w * sign_determinant_model_3x3() ); } diff --git a/crates/bevy_pbr/src/render/mesh_types.wgsl b/crates/bevy_pbr/src/render/mesh_types.wgsl index e0bfd2c2899cd..d44adbc2bb13f 100644 --- a/crates/bevy_pbr/src/render/mesh_types.wgsl +++ b/crates/bevy_pbr/src/render/mesh_types.wgsl @@ -14,3 +14,5 @@ struct SkinnedMesh { #endif let MESH_FLAGS_SHADOW_RECEIVER_BIT: u32 = 1u; +// 2^31 - if the flag is set, the sign is positive, else it is negative +let MESH_FLAGS_SIGN_DETERMINANT_MODEL_3X3_BIT: u32 = 2147483648u; diff --git a/crates/bevy_pbr/src/render/pbr_functions.wgsl b/crates/bevy_pbr/src/render/pbr_functions.wgsl index cd922bf74412c..a77c065fca221 100644 --- a/crates/bevy_pbr/src/render/pbr_functions.wgsl +++ b/crates/bevy_pbr/src/render/pbr_functions.wgsl @@ -15,7 +15,13 @@ fn prepare_normal( #endif is_front: bool, ) -> vec3 { - var N: vec3 = normalize(world_normal); + // NOTE: The mikktspace method of normal mapping explicitly requires that the world normal NOT + // be re-normalized in the fragment shader. This is primarily to match the way mikktspace + // bakes vertex tangents and normal maps so that this is the exact inverse. Blender, Unity, + // Unreal Engine, Godot, and more all use the mikktspace method. Do not change this code + // unless you really know what you are doing. + // http://www.mikktspace.com/ + var N: vec3 = world_normal; #ifdef VERTEX_TANGENTS #ifdef STANDARDMATERIAL_NORMAL_MAP @@ -236,7 +242,7 @@ fn pbr( fn tone_mapping(in: vec4) -> vec4 { // tone_mapping return vec4(reinhard_luminance(in.rgb), in.a); - + // Gamma correction. // Not needed with sRGB buffer // output_color.rgb = pow(output_color.rgb, vec3(1.0 / 2.2));