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, ); ```
59 lines
1.7 KiB
WebGPU Shading Language
59 lines
1.7 KiB
WebGPU Shading Language
#import bevy_pbr::mesh_view_bindings
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#import bevy_pbr::mesh_bindings
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#import bevy_pbr::pbr_types
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#import bevy_pbr::utils
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#import bevy_pbr::clustered_forward
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#import bevy_pbr::lighting
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#import bevy_pbr::shadows
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#import bevy_pbr::pbr_functions
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@group(1) @binding(0)
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var my_array_texture: texture_2d_array<f32>;
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@group(1) @binding(1)
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var my_array_texture_sampler: sampler;
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struct FragmentInput {
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@builtin(front_facing) is_front: bool,
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@builtin(position) frag_coord: vec4<f32>,
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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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let layer = i32(in.world_position.x) & 0x3;
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// Prepare a 'processed' StandardMaterial by sampling all textures to resolve
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// the material members
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var pbr_input: PbrInput = pbr_input_new();
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pbr_input.material.base_color = textureSample(my_array_texture, my_array_texture_sampler, in.uv, layer);
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#ifdef VERTEX_COLORS
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pbr_input.material.base_color = pbr_input.material.base_color * in.color;
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#endif
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pbr_input.frag_coord = in.frag_coord;
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pbr_input.world_position = in.world_position;
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pbr_input.world_normal = prepare_world_normal(
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in.world_normal,
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(pbr_input.material.flags & STANDARD_MATERIAL_FLAGS_DOUBLE_SIDED_BIT) != 0u,
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in.is_front,
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);
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pbr_input.is_orthographic = view.projection[3].w == 1.0;
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pbr_input.N = apply_normal_mapping(
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pbr_input.material.flags,
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pbr_input.world_normal,
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#ifdef VERTEX_TANGENTS
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#ifdef STANDARDMATERIAL_NORMAL_MAP
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in.world_tangent,
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#endif
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#endif
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in.uv,
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);
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pbr_input.V = calculate_view(in.world_position, pbr_input.is_orthographic);
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return tone_mapping(pbr(pbr_input));
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}
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