1//! Functions to be used by materials for reading from a meshlet visibility buffer texture.3import package::{4 meshlet::bindings::{5 Meshlet,6 meshlet_visibility_buffer,7 meshlet_raster_clusters,8 meshlets,9 meshlet_instance_uniforms,10 get_meshlet_vertex_id,11 get_meshlet_vertex_position,12 get_meshlet_vertex_normal,13 get_meshlet_vertex_uv,14 },15 render::{16 mesh_view_bindings::view,17 mesh_functions::mesh_position_local_to_world,18 mesh_types::Mesh,19 view_transformations::{position_world_to_clip, frag_coord_to_ndc},20 },21};22import bevy_render::maths::{affine3_to_square, mat2x4_f32_to_mat3x3_unpack};24@if(PREPASS_FRAGMENT && MOTION_VECTOR_PREPASS)25import package::{26 prepass::bindings::previous_view_uniforms,27 render::pbr_prepass_functions::calculate_motion_vector,28};30@if(MESHLET_MESH_MATERIAL_PASS)31struct PartialDerivatives {32 barycentrics: vec3<f32>,33 ddx: vec3<f32>,34 ddy: vec3<f32>,35}37/// https://github.com/ConfettiFX/The-Forge/blob/9d43e69141a9cd0ce2ce2d2db5122234d3a2d5b5/Common_3/Renderer/VisibilityBuffer2/Shaders/FSL/vb_shading_utilities.h.fsl#L90-L15038@if(MESHLET_MESH_MATERIAL_PASS)39fn compute_partial_derivatives(vertex_world_positions: array<vec4<f32>, 3>, ndc_uv: vec2<f32>, two_over_screen_size: vec2<f32>) -> PartialDerivatives {40 var result: PartialDerivatives;42 let vertex_clip_position_0 = position_world_to_clip(vertex_world_positions[0].xyz);43 let vertex_clip_position_1 = position_world_to_clip(vertex_world_positions[1].xyz);44 let vertex_clip_position_2 = position_world_to_clip(vertex_world_positions[2].xyz);46 let inv_w = 1.0 / vec3(vertex_clip_position_0.w, vertex_clip_position_1.w, vertex_clip_position_2.w);47 let ndc_0 = vertex_clip_position_0.xy * inv_w[0];48 let ndc_1 = vertex_clip_position_1.xy * inv_w[1];49 let ndc_2 = vertex_clip_position_2.xy * inv_w[2];51 let inv_det = 1.0 / determinant(mat2x2(ndc_2 - ndc_1, ndc_0 - ndc_1));52 result.ddx = vec3(ndc_1.y - ndc_2.y, ndc_2.y - ndc_0.y, ndc_0.y - ndc_1.y) * inv_det * inv_w;53 result.ddy = vec3(ndc_2.x - ndc_1.x, ndc_0.x - ndc_2.x, ndc_1.x - ndc_0.x) * inv_det * inv_w;55 var ddx_sum = dot(result.ddx, vec3(1.0));56 var ddy_sum = dot(result.ddy, vec3(1.0));58 let delta_v = ndc_uv - ndc_0;59 let interp_inv_w = inv_w.x + delta_v.x * ddx_sum + delta_v.y * ddy_sum;60 let interp_w = 1.0 / interp_inv_w;62 result.barycentrics = vec3(63 interp_w * (inv_w[0] + delta_v.x * result.ddx.x + delta_v.y * result.ddy.x),64 interp_w * (delta_v.x * result.ddx.y + delta_v.y * result.ddy.y),65 interp_w * (delta_v.x * result.ddx.z + delta_v.y * result.ddy.z),66 );68 result.ddx *= two_over_screen_size.x;69 result.ddy *= two_over_screen_size.y;70 ddx_sum *= two_over_screen_size.x;71 ddy_sum *= two_over_screen_size.y;73 result.ddy *= -1.0;74 ddy_sum *= -1.0;76 let interp_ddx_w = 1.0 / (interp_inv_w + ddx_sum);77 let interp_ddy_w = 1.0 / (interp_inv_w + ddy_sum);79 result.ddx = interp_ddx_w * (result.barycentrics * interp_inv_w + result.ddx) - result.barycentrics;80 result.ddy = interp_ddy_w * (result.barycentrics * interp_inv_w + result.ddy) - result.barycentrics;81 return result;82}84@if(MESHLET_MESH_MATERIAL_PASS)85struct VertexOutput {86 position: vec4<f32>,87 world_position: vec4<f32>,88 world_normal: vec3<f32>,89 uv: vec2<f32>,90 ddx_uv: vec2<f32>,91 ddy_uv: vec2<f32>,92 world_tangent: vec4<f32>,93 mesh_flags: u32,94 cluster_id: u32,95 material_bind_group_slot: u32,96 @if(PREPASS_FRAGMENT && MOTION_VECTOR_PREPASS)97 motion_vector: vec2<f32>,98}100/// Load the visibility buffer texture and resolve it into a VertexOutput.101@if(MESHLET_MESH_MATERIAL_PASS)102fn resolve_vertex_output(frag_coord: vec4<f32>) -> VertexOutput {103 let packed_ids = u32(textureLoad(meshlet_visibility_buffer, vec2<u32>(frag_coord.xy)).r);104 let cluster_id = packed_ids >> 7u;105 let instanced_offset = meshlet_raster_clusters[cluster_id];106 let meshlet_id = instanced_offset.offset;107 var meshlet = meshlets[meshlet_id];109 let triangle_id = extractBits(packed_ids, 0u, 7u);110 let index_ids = meshlet.start_index_id + (triangle_id * 3u) + vec3(0u, 1u, 2u);111 let vertex_ids = vec3(get_meshlet_vertex_id(index_ids[0]), get_meshlet_vertex_id(index_ids[1]), get_meshlet_vertex_id(index_ids[2]));112 let vertex_0 = load_vertex(&meshlet, vertex_ids[0]);113 let vertex_1 = load_vertex(&meshlet, vertex_ids[1]);114 let vertex_2 = load_vertex(&meshlet, vertex_ids[2]);116 let instance_id = instanced_offset.instance_id;117 var instance_uniform = meshlet_instance_uniforms[instance_id];119 let world_from_local = affine3_to_square(instance_uniform.world_from_local);120 let world_position_0 = mesh_position_local_to_world(world_from_local, vec4(vertex_0.position, 1.0));121 let world_position_1 = mesh_position_local_to_world(world_from_local, vec4(vertex_1.position, 1.0));122 let world_position_2 = mesh_position_local_to_world(world_from_local, vec4(vertex_2.position, 1.0));124 let frag_coord_ndc = frag_coord_to_ndc(frag_coord).xy;125 let partial_derivatives = compute_partial_derivatives(126 array(world_position_0, world_position_1, world_position_2),127 frag_coord_ndc,128 2.0 / view.viewport.zw,129 );131 let world_position = mat3x4(world_position_0, world_position_1, world_position_2) * partial_derivatives.barycentrics;132 let world_positions_camera_relative = mat3x3(133 world_position_0.xyz - view.world_position,134 world_position_1.xyz - view.world_position,135 world_position_2.xyz - view.world_position,136 );137 let ddx_world_position = world_positions_camera_relative * partial_derivatives.ddx;138 let ddy_world_position = world_positions_camera_relative * partial_derivatives.ddy;140 let world_normal = mat3x3(141 normal_local_to_world(vertex_0.normal, &instance_uniform),142 normal_local_to_world(vertex_1.normal, &instance_uniform),143 normal_local_to_world(vertex_2.normal, &instance_uniform),144 ) * partial_derivatives.barycentrics;146 let uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.barycentrics;147 let ddx_uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.ddx;148 let ddy_uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.ddy;150 let world_tangent = calculate_world_tangent(world_normal, ddx_world_position, ddy_world_position, ddx_uv, ddy_uv);152 var motion_vector: vec2<f32>;153@if(PREPASS_FRAGMENT && MOTION_VECTOR_PREPASS) {154 let previous_world_from_local = affine3_to_square(instance_uniform.previous_world_from_local);155 let previous_world_position_0 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_0.position, 1.0));156 let previous_world_position_1 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_1.position, 1.0));157 let previous_world_position_2 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_2.position, 1.0));158 let previous_world_position = mat3x4(previous_world_position_0, previous_world_position_1, previous_world_position_2) * partial_derivatives.barycentrics;159 motion_vector = calculate_motion_vector(world_position, previous_world_position);160}162 var out: VertexOutput;163 out.position = frag_coord;164 out.world_position = world_position;165 out.world_normal = world_normal;166 out.uv = uv;167 out.ddx_uv = ddx_uv;168 out.ddy_uv = ddy_uv;169 out.world_tangent = world_tangent;170 out.mesh_flags = instance_uniform.flags;171 out.cluster_id = instance_id ^ meshlet_id;172 out.material_bind_group_slot = instance_uniform.material_and_lightmap_bind_group_slot & 0xffffu;173 @if(PREPASS_FRAGMENT && MOTION_VECTOR_PREPASS)174 out.motion_vector = motion_vector;175 return out;176}178@if(MESHLET_MESH_MATERIAL_PASS)179struct MeshletVertex {180 position: vec3<f32>,181 normal: vec3<f32>,182 uv: vec2<f32>,183}185@if(MESHLET_MESH_MATERIAL_PASS)186fn load_vertex(meshlet: ptr<function, Meshlet>, vertex_id: u32) -> MeshletVertex {187 return MeshletVertex(188 get_meshlet_vertex_position(meshlet, vertex_id),189 get_meshlet_vertex_normal(meshlet, vertex_id),190 get_meshlet_vertex_uv(meshlet, vertex_id),191 );192}194@if(MESHLET_MESH_MATERIAL_PASS)195fn normal_local_to_world(vertex_normal: vec3<f32>, instance_uniform: ptr<function, Mesh>) -> vec3<f32> {196 if any(vertex_normal != vec3<f32>(0.0)) {197 return normalize(198 mat2x4_f32_to_mat3x3_unpack(199 (*instance_uniform).local_from_world_transpose_a,200 (*instance_uniform).local_from_world_transpose_b,201 ) * vertex_normal202 );203 } else {204 return vertex_normal;205 }206}208/// https://www.jeremyong.com/graphics/2023/12/16/surface-gradient-bump-mapping/#surface-gradient-from-a-tangent-space-normal-vector-without-an-explicit-tangent-basis209@if(MESHLET_MESH_MATERIAL_PASS)210fn calculate_world_tangent(211 world_normal: vec3<f32>,212 ddx_world_position: vec3<f32>,213 ddy_world_position: vec3<f32>,214 ddx_uv: vec2<f32>,215 ddy_uv: vec2<f32>,216) -> vec4<f32> {217 // Project the position gradients onto the tangent plane218 let ddx_world_position_s = ddx_world_position - dot(ddx_world_position, world_normal) * world_normal;219 let ddy_world_position_s = ddy_world_position - dot(ddy_world_position, world_normal) * world_normal;221 // Compute the jacobian matrix to leverage the chain rule222 let jacobian_sign = sign(ddx_uv.x * ddy_uv.y - ddx_uv.y * ddy_uv.x);224 var world_tangent = jacobian_sign * (ddy_uv.y * ddx_world_position_s - ddx_uv.y * ddy_world_position_s);226 // The sign intrinsic returns 0 if the argument is 0227 if jacobian_sign != 0.0 {228 world_tangent = normalize(world_tangent);229 }231 // The second factor here ensures a consistent handedness between232 // the tangent frame and surface basis w.r.t. screenspace.233 let w = jacobian_sign * sign(dot(ddy_world_position, cross(world_normal, ddx_world_position)));235 return vec4(world_tangent, -w); // TODO: Unclear why we need to negate this to match mikktspace generated tangents236}
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