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[[mesh, max_total_threads_per_threadgroup(32)]] |
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void select_triangles( |
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object_data SelectedMeshlets const & selected_meshlets [[payload]], |
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ushort const t_in_sg [[thread_index_in_simdgroup]], |
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ushort const tg_in_g [[threadgroup_position_in_grid]], |
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constant Model const & model [[buffer(0)]], |
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Mesh out |
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) { |
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Meshlet const meshlet = selected_meshlets.meshlets[tg_in_g]; |
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half2 cached_pos_2d; |
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if (t_in_sg < meshlet.vertices_count()) { |
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uint const index = model.meshlet_vertices[meshlet.vertices_start() + t_in_sg]; |
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float3 const position = float4((constant rgba16snorm<float4> &) model.encoded_vertex_positions[index]).xyz; |
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float4 const pos = selected_meshlets.model_to_camera_projection * float4(position, 1); |
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out.set_vertex(t_in_sg, { .position = pos }); |
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cached_pos_2d = half2(pos.xy / pos.w); |
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} |
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|
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constant packed_uchar3 const * tris = &model.meshlet_triangles[meshlet.triangles_start()]; |
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uchar3 const tri = t_in_sg < meshlet.triangles_count() ? tris[t_in_sg] : uchar3(0); |
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__builtin_assume(tri.x < 32 && tri.y < 32 && tri.z < 32); |
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half2 const a = simd_shuffle(cached_pos_2d, tri.x); |
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half2 const b = simd_shuffle(cached_pos_2d, tri.y); |
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half2 const c = simd_shuffle(cached_pos_2d, tri.z); |
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|
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if (!(t_in_sg < meshlet.triangles_count())) return; |
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if (!mimeo::is_tri_front_facing_2d(a, b, c)) return; |
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if (!mimeo::is_tri_within_frustum_ndc_2d(a, b, c)) return; |
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|
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// TODO(0): Change back to `ushort`, workaround for FB15482904 |
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short const primitive = simd_prefix_exclusive_sum(1); |
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out.set_primitive(primitive, MeshPrimitive { |
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.meshlet_id = selected_meshlets.meshlet_ids[tg_in_g], |
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}); |
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ushort3 const indices = ushort3(primitive * 3u) + ushort3(0u, 1u, 2u); |
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out.set_index(indices.x, tri.x); |
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out.set_index(indices.y, tri.y); |
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out.set_index(indices.z, tri.z); |
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|
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ushort const num_tris = simd_sum(1u); |
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if (simd_is_first()) out.set_primitive_count(num_tris); |
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} |
