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https://github.com/bevyengine/bevy
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fc56c686af
# Objective - Fixes #4019 - Fix lighting of double-sided materials when using a negative scale - The FlightHelmet.gltf model's hose uses a double-sided material. Loading the model with a uniform scale of -1.0, and comparing against Blender, it was identified that negating the world-space tangent, bitangent, and interpolated normal produces incorrect lighting. Discussion with Morten Mikkelsen clarified that this is both incorrect and unnecessary. ## Solution - Remove the code that negates the T, B, and N vectors (the interpolated world-space tangent, calculated world-space bitangent, and interpolated world-space normal) when seeing the back face of a double-sided material with negative scale. - Negate the world normal for a double-sided back face only when not using normal mapping ### Before, on `main`, flipping T, B, and N <img width="932" alt="Screenshot 2022-08-22 at 15 11 53" src="https://user-images.githubusercontent.com/302146/185965366-f776ff2c-cfa1-46d1-9c84-fdcb399c273c.png"> ### After, on this PR <img width="932" alt="Screenshot 2022-08-22 at 15 12 11" src="https://user-images.githubusercontent.com/302146/185965420-8be493e2-3b1a-4188-bd13-fd6b17a76fe7.png"> ### Double-sided material without normal maps https://user-images.githubusercontent.com/302146/185988113-44a384e7-0b55-4946-9b99-20f8c803ab7e.mp4 --- ## Changelog - Fixed: Lighting of normal-mapped, double-sided materials applied to models with negative scale - Fixed: Lighting and shadowing of back faces with no normal-mapping and a double-sided material ## Migration Guide `prepare_normal` from the `bevy_pbr::pbr_functions` shader import has been reworked. Before: ```rust pbr_input.world_normal = in.world_normal; pbr_input.N = prepare_normal( pbr_input.material.flags, in.world_normal, #ifdef VERTEX_TANGENTS #ifdef STANDARDMATERIAL_NORMAL_MAP in.world_tangent, #endif #endif in.uv, in.is_front, ); ``` After: ```rust pbr_input.world_normal = prepare_world_normal( in.world_normal, (material.flags & STANDARD_MATERIAL_FLAGS_DOUBLE_SIDED_BIT) != 0u, in.is_front, ); pbr_input.N = apply_normal_mapping( pbr_input.material.flags, pbr_input.world_normal, #ifdef VERTEX_TANGENTS #ifdef STANDARDMATERIAL_NORMAL_MAP in.world_tangent, #endif #endif in.uv, ); ```
83 lines
1.8 KiB
WebGPU Shading Language
83 lines
1.8 KiB
WebGPU Shading Language
#import bevy_pbr::mesh_view_bindings
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#import bevy_pbr::mesh_bindings
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// NOTE: Bindings must come before functions that use them!
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#import bevy_pbr::mesh_functions
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struct Vertex {
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#ifdef VERTEX_POSITIONS
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@location(0) position: vec3<f32>,
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#endif
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#ifdef VERTEX_NORMALS
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@location(1) normal: vec3<f32>,
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#endif
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#ifdef VERTEX_UVS
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@location(2) uv: vec2<f32>,
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#endif
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#ifdef VERTEX_TANGENTS
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@location(3) tangent: vec4<f32>,
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#endif
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#ifdef VERTEX_COLORS
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@location(4) color: vec4<f32>,
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#endif
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#ifdef SKINNED
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@location(5) joint_indices: vec4<u32>,
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@location(6) joint_weights: vec4<f32>,
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#endif
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};
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struct VertexOutput {
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@builtin(position) clip_position: vec4<f32>,
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#import bevy_pbr::mesh_vertex_output
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};
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@vertex
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fn vertex(vertex: Vertex) -> VertexOutput {
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var out: VertexOutput;
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#ifdef SKINNED
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var model = skin_model(vertex.joint_indices, vertex.joint_weights);
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#else
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var model = mesh.model;
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#endif
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#ifdef VERTEX_NORMALS
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#ifdef SKINNED
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out.world_normal = skin_normals(model, vertex.normal);
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#else
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out.world_normal = mesh_normal_local_to_world(vertex.normal);
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#endif
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#endif
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#ifdef VERTEX_POSITIONS
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out.world_position = mesh_position_local_to_world(model, vec4<f32>(vertex.position, 1.0));
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out.clip_position = mesh_position_world_to_clip(out.world_position);
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#endif
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#ifdef VERTEX_UVS
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out.uv = vertex.uv;
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#endif
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#ifdef VERTEX_TANGENTS
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out.world_tangent = mesh_tangent_local_to_world(model, vertex.tangent);
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#endif
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#ifdef VERTEX_COLORS
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out.color = vertex.color;
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#endif
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return out;
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}
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struct FragmentInput {
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#import bevy_pbr::mesh_vertex_output
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};
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@fragment
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fn fragment(in: FragmentInput) -> @location(0) vec4<f32> {
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#ifdef VERTEX_COLORS
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return in.color;
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#else
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return vec4<f32>(1.0, 0.0, 1.0, 1.0);
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#endif
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}
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