1#define_import_path bevy_pbr::meshlet_visibility_buffer_resolve3#import bevy_pbr::{4 meshlet_bindings::{5 Meshlet,6 meshlet_visibility_buffer,7 meshlet_cluster_meshlet_ids,8 meshlets,9 meshlet_cluster_instance_ids,10 meshlet_instance_uniforms,11 get_meshlet_vertex_id,12 get_meshlet_vertex_position,13 get_meshlet_vertex_normal,14 get_meshlet_vertex_uv,15 },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#import bevy_render::maths::{affine3_to_square, mat2x4_f32_to_mat3x3_unpack}23#ifdef PREPASS_FRAGMENT24#ifdef MOTION_VECTOR_PREPASS25#import bevy_pbr::{26 prepass_bindings::previous_view_uniforms,27 pbr_prepass_functions::calculate_motion_vector,28}29#endif30#endif32/// Functions to be used by materials for reading from a meshlet visibility buffer texture.34#ifdef MESHLET_MESH_MATERIAL_PASS35struct PartialDerivatives {36 barycentrics: vec3<f32>,37 ddx: vec3<f32>,38 ddy: vec3<f32>,39}41// https://github.com/ConfettiFX/The-Forge/blob/9d43e69141a9cd0ce2ce2d2db5122234d3a2d5b5/Common_3/Renderer/VisibilityBuffer2/Shaders/FSL/vb_shading_utilities.h.fsl#L90-L15042fn compute_partial_derivatives(vertex_world_positions: array<vec4<f32>, 3>, ndc_uv: vec2<f32>, half_screen_size: vec2<f32>) -> PartialDerivatives {43 var result: PartialDerivatives;45 let vertex_clip_position_0 = position_world_to_clip(vertex_world_positions[0].xyz);46 let vertex_clip_position_1 = position_world_to_clip(vertex_world_positions[1].xyz);47 let vertex_clip_position_2 = position_world_to_clip(vertex_world_positions[2].xyz);49 let inv_w = 1.0 / vec3(vertex_clip_position_0.w, vertex_clip_position_1.w, vertex_clip_position_2.w);50 let ndc_0 = vertex_clip_position_0.xy * inv_w[0];51 let ndc_1 = vertex_clip_position_1.xy * inv_w[1];52 let ndc_2 = vertex_clip_position_2.xy * inv_w[2];54 let inv_det = 1.0 / determinant(mat2x2(ndc_2 - ndc_1, ndc_0 - ndc_1));55 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;56 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;58 var ddx_sum = dot(result.ddx, vec3(1.0));59 var ddy_sum = dot(result.ddy, vec3(1.0));61 let delta_v = ndc_uv - ndc_0;62 let interp_inv_w = inv_w.x + delta_v.x * ddx_sum + delta_v.y * ddy_sum;63 let interp_w = 1.0 / interp_inv_w;65 result.barycentrics = vec3(66 interp_w * (inv_w[0] + delta_v.x * result.ddx.x + delta_v.y * result.ddy.x),67 interp_w * (delta_v.x * result.ddx.y + delta_v.y * result.ddy.y),68 interp_w * (delta_v.x * result.ddx.z + delta_v.y * result.ddy.z),69 );71 result.ddx *= half_screen_size.x;72 result.ddy *= half_screen_size.y;73 ddx_sum *= half_screen_size.x;74 ddy_sum *= half_screen_size.y;76 result.ddy *= -1.0;77 ddy_sum *= -1.0;79 let interp_ddx_w = 1.0 / (interp_inv_w + ddx_sum);80 let interp_ddy_w = 1.0 / (interp_inv_w + ddy_sum);82 result.ddx = interp_ddx_w * (result.barycentrics * interp_inv_w + result.ddx) - result.barycentrics;83 result.ddy = interp_ddy_w * (result.barycentrics * interp_inv_w + result.ddy) - result.barycentrics;84 return result;85}87struct VertexOutput {88 position: vec4<f32>,89 world_position: vec4<f32>,90 world_normal: vec3<f32>,91 uv: vec2<f32>,92 ddx_uv: vec2<f32>,93 ddy_uv: vec2<f32>,94 world_tangent: vec4<f32>,95 mesh_flags: u32,96 cluster_id: u32,97 material_bind_group_slot: u32,98#ifdef PREPASS_FRAGMENT99#ifdef MOTION_VECTOR_PREPASS100 motion_vector: vec2<f32>,101#endif102#endif103}105/// Load the visibility buffer texture and resolve it into a VertexOutput.106fn resolve_vertex_output(frag_coord: vec4<f32>) -> VertexOutput {107 let packed_ids = u32(textureLoad(meshlet_visibility_buffer, vec2<u32>(frag_coord.xy)).r);108 let cluster_id = packed_ids >> 7u;109 let meshlet_id = meshlet_cluster_meshlet_ids[cluster_id];110 var meshlet = meshlets[meshlet_id];112 let triangle_id = extractBits(packed_ids, 0u, 7u);113 let index_ids = meshlet.start_index_id + (triangle_id * 3u) + vec3(0u, 1u, 2u);114 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]));115 let vertex_0 = load_vertex(&meshlet, vertex_ids[0]);116 let vertex_1 = load_vertex(&meshlet, vertex_ids[1]);117 let vertex_2 = load_vertex(&meshlet, vertex_ids[2]);119 let instance_id = meshlet_cluster_instance_ids[cluster_id];120 var instance_uniform = meshlet_instance_uniforms[instance_id];122 let world_from_local = affine3_to_square(instance_uniform.world_from_local);123 let world_position_0 = mesh_position_local_to_world(world_from_local, vec4(vertex_0.position, 1.0));124 let world_position_1 = mesh_position_local_to_world(world_from_local, vec4(vertex_1.position, 1.0));125 let world_position_2 = mesh_position_local_to_world(world_from_local, vec4(vertex_2.position, 1.0));127 let frag_coord_ndc = frag_coord_to_ndc(frag_coord).xy;128 let partial_derivatives = compute_partial_derivatives(129 array(world_position_0, world_position_1, world_position_2),130 frag_coord_ndc,131 view.viewport.zw / 2.0,132 );134 let world_position = mat3x4(world_position_0, world_position_1, world_position_2) * partial_derivatives.barycentrics;135 let world_positions_camera_relative = mat3x3(136 world_position_0.xyz - view.world_position,137 world_position_1.xyz - view.world_position,138 world_position_2.xyz - view.world_position,139 );140 let ddx_world_position = world_positions_camera_relative * partial_derivatives.ddx;141 let ddy_world_position = world_positions_camera_relative * partial_derivatives.ddy;143 let world_normal = mat3x3(144 normal_local_to_world(vertex_0.normal, &instance_uniform),145 normal_local_to_world(vertex_1.normal, &instance_uniform),146 normal_local_to_world(vertex_2.normal, &instance_uniform),147 ) * partial_derivatives.barycentrics;149 let uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.barycentrics;150 let ddx_uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.ddx;151 let ddy_uv = mat3x2(vertex_0.uv, vertex_1.uv, vertex_2.uv) * partial_derivatives.ddy;153 let world_tangent = calculate_world_tangent(world_normal, ddx_world_position, ddy_world_position, ddx_uv, ddy_uv);155#ifdef PREPASS_FRAGMENT156#ifdef MOTION_VECTOR_PREPASS157 let previous_world_from_local = affine3_to_square(instance_uniform.previous_world_from_local);158 let previous_world_position_0 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_0.position, 1.0));159 let previous_world_position_1 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_1.position, 1.0));160 let previous_world_position_2 = mesh_position_local_to_world(previous_world_from_local, vec4(vertex_2.position, 1.0));161 let previous_world_position = mat3x4(previous_world_position_0, previous_world_position_1, previous_world_position_2) * partial_derivatives.barycentrics;162 let motion_vector = calculate_motion_vector(world_position, previous_world_position);163#endif164#endif166 return VertexOutput(167 frag_coord,168 world_position,169 world_normal,170 uv,171 ddx_uv,172 ddy_uv,173 world_tangent,174 instance_uniform.flags,175 instance_id ^ meshlet_id,176 instance_uniform.material_and_lightmap_bind_group_slot & 0xffffu,177#ifdef PREPASS_FRAGMENT178#ifdef MOTION_VECTOR_PREPASS179 motion_vector,180#endif181#endif182 );183}185struct MeshletVertex {186 position: vec3<f32>,187 normal: vec3<f32>,188 uv: vec2<f32>,189}191fn load_vertex(meshlet: ptr<function, Meshlet>, vertex_id: u32) -> MeshletVertex {192 return MeshletVertex(193 get_meshlet_vertex_position(meshlet, vertex_id),194 get_meshlet_vertex_normal(meshlet, vertex_id),195 get_meshlet_vertex_uv(meshlet, vertex_id),196 );197}199fn normal_local_to_world(vertex_normal: vec3<f32>, instance_uniform: ptr<function, Mesh>) -> vec3<f32> {200 if any(vertex_normal != vec3<f32>(0.0)) {201 return normalize(202 mat2x4_f32_to_mat3x3_unpack(203 (*instance_uniform).local_from_world_transpose_a,204 (*instance_uniform).local_from_world_transpose_b,205 ) * vertex_normal206 );207 } else {208 return vertex_normal;209 }210}212// https://www.jeremyong.com/graphics/2023/12/16/surface-gradient-bump-mapping/#surface-gradient-from-a-tangent-space-normal-vector-without-an-explicit-tangent-basis213fn calculate_world_tangent(214 world_normal: vec3<f32>,215 ddx_world_position: vec3<f32>,216 ddy_world_position: vec3<f32>,217 ddx_uv: vec2<f32>,218 ddy_uv: vec2<f32>,219) -> vec4<f32> {220 // Project the position gradients onto the tangent plane221 let ddx_world_position_s = ddx_world_position - dot(ddx_world_position, world_normal) * world_normal;222 let ddy_world_position_s = ddy_world_position - dot(ddy_world_position, world_normal) * world_normal;224 // Compute the jacobian matrix to leverage the chain rule225 let jacobian_sign = sign(ddx_uv.x * ddy_uv.y - ddx_uv.y * ddy_uv.x);227 var world_tangent = jacobian_sign * (ddy_uv.y * ddx_world_position_s - ddx_uv.y * ddy_world_position_s);229 // The sign intrinsic returns 0 if the argument is 0230 if jacobian_sign != 0.0 {231 world_tangent = normalize(world_tangent);232 }234 // The second factor here ensures a consistent handedness between235 // the tangent frame and surface basis w.r.t. screenspace.236 let w = jacobian_sign * sign(dot(ddy_world_position, cross(world_normal, ddx_world_position)));238 return vec4(world_tangent, -w); // TODO: Unclear why we need to negate this to match mikktspace generated tangents239}240#endif
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