Create MeshBuilder utility for comfy mesh building

5 files changed, 97 insertions, 33 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1591197..e78f153 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,6 +52,7 @@ add_executable(meowcraft
     src/World/Generation/Decoration.hpp
     src/Math/Random.cpp
     src/Math/Random.hpp
+    src/GFX/Util/MeshBuilder.hpp
 )
 target_link_libraries(meowcraft glfw GLEW::GLEW)
 
diff --git a/src/Common/Sizes.hpp b/src/Common/Sizes.hpp
index 91422e5..de49d3d 100644
--- a/src/Common/Sizes.hpp
+++ b/src/Common/Sizes.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cstdint>
+#include <sys/types.h>
 
 using I8 = int8_t;
 using U8 = uint8_t;
@@ -14,8 +15,8 @@ using U32 = uint32_t;
 using I64 = int64_t;
 using U64 = uint64_t;
 
-using ISize = I64;
-using USize = U64;
+using ISize = ssize_t;
+using USize = size_t;
 
 using F32 = float;
 using F64 = double;
diff --git a/src/GFX/Util/MeshBuilder.hpp b/src/GFX/Util/MeshBuilder.hpp
new file mode 100644
index 0000000..e3caa8c
--- /dev/null
+++ b/src/GFX/Util/MeshBuilder.hpp
@@ -0,0 +1,65 @@
+#pragma once
+
+#include "../../Common/Sizes.hpp"
+#include "../../Math/Common.hpp"
+#include <vector>
+
+namespace MC::GFX::Util {
+
+template <typename... Attributes>
+class MeshBuilder {
+    using AttributeTuple = std::tuple<std::vector<Attributes>...>;
+
+    template <int N, typename AttributeContainer>
+    using EnableIfCorrectAttributeIndex =
+        std::enable_if_t<std::is_same_v<
+            typename std::tuple_element_t<N, AttributeTuple>::value_type,
+            typename AttributeContainer::value_type>, Bool>;
+
+    template <int N, typename A>
+    std::vector<A>& get() {
+        return std::get<N>(m_attributes);
+    }
+
+    template <USize... Sequence>
+    Mesh mesh(std::index_sequence<Sequence...>) {
+        return {
+            {m_positions, std::get<Sequence>(m_attributes)...},
+            m_indices,
+        };
+    }
+
+    std::vector<Vector<3, F32>> m_positions{};
+    std::vector<U32> m_indices{};
+    AttributeTuple m_attributes;
+public:
+    static constexpr UInt AttributesN = sizeof...(Attributes);
+
+    MeshBuilder() = default;
+
+    template<int N, typename AC, EnableIfCorrectAttributeIndex<N, AC> = true>
+    void attributes(const AC& from) {
+        auto& attribute_list = get<N, typename AC::value_type>();
+        attribute_list.insert(attribute_list.end(), from.begin(), from.end());
+    }
+
+    template<typename AC>
+    void positions(const AC& from) {
+        m_positions.insert(m_positions.end(), from.begin(), from.end());
+    }
+
+    template<typename AC>
+    void indices(const AC& from) {
+        m_indices.insert(m_indices.end(), from.begin(), from.end());
+    }
+
+    Mesh mesh() {
+        return mesh(std::make_index_sequence<AttributesN>{});
+    }
+
+    USize vertex_count() const {
+        return m_positions.size();
+    }
+};
+
+}
diff --git a/src/World/Generation/ChunkMeshing.cpp b/src/World/Generation/ChunkMeshing.cpp
index 7158734..2e9f191 100644
--- a/src/World/Generation/ChunkMeshing.cpp
+++ b/src/World/Generation/ChunkMeshing.cpp
@@ -13,10 +13,10 @@ ChunkMesh mesh_chunk(Chunk& chunk, const ChunkNeighbors& neighbors) {
 
 namespace Detail {
 
-std::array<Vector<3, F32>, 4> DefaultMeshDecisions::face_positions(BlockSide side, U32 x, U32 y, U32 z) {
+Face<Vertex> DefaultMeshDecisions::face_positions(BlockSide side, U32 x, U32 y, U32 z) {
     // Winding order: (0, 1, 2) (2, 3, 0)
     // Note: OpenGL Coordinate system has a flipped z axis.
-    std::array<Vector<3, F32>, 4> face{};
+    Face<Vertex> face{};
     switch (side) {
     case BlockSide::Front:
         face = {{{0, 1, 1}, {0, 0, 1}, {1, 0, 1}, {1, 1, 1}}};
@@ -44,14 +44,14 @@ std::array<Vector<3, F32>, 4> DefaultMeshDecisions::face_positions(BlockSide sid
     return face;
 }
 
-std::array<Vector<2, F32>, 4> DefaultMeshDecisions::face_tex_coords(BlockType type, BlockSide side) {
+Face<TexCoord> DefaultMeshDecisions::face_tex_coords(BlockType type, BlockSide side) {
     U8 atlas_width = 4;
     U8 atlas_height = 4;
 
     Real width_step = 1.0f / atlas_width;
     Real height_step = 1.0f / atlas_height;
 
-    auto block_coords = [=](U8 x, U8 y) -> std::array<Vector<2, F32>, 4> {
+    auto block_coords = [=](U8 x, U8 y) -> Face<TexCoord> {
         auto t = y * height_step;
         auto l = x * width_step;
         auto b = t + height_step;
@@ -119,12 +119,12 @@ std::array<Vector<2, F32>, 4> DefaultMeshDecisions::face_tex_coords(BlockType ty
     }
 }
 
-std::array<Vector<3, F32>, 4> DefaultMeshDecisions::face_normals(BlockSide side) {
+Face<Normal> DefaultMeshDecisions::face_normals(BlockSide side) {
     Vector<3, F32> normal{get_face_normal(side)};
     return {normal, normal, normal, normal};
 }
 
-std::array<F32, 4> DefaultMeshDecisions::face_ao_values(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side) {
+Face<AO> DefaultMeshDecisions::face_ao_values(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side) {
     std::array<Vector<3, I32>, 8> offsets{};
     // Given a block position, these offsets can be added to it to get the 8 blocks necessary to calculate AO.
     // There are 4 corners and 4 sides, corners are visually distinguished by the lack of spaces and
@@ -151,7 +151,7 @@ std::array<F32, 4> DefaultMeshDecisions::face_ao_values(Chunk& chunk, const Chun
         break;
     }
 
-    std::array<F32, 4> vertex_ao{};
+    Face<AO> vertex_ao{};
 
     UInt offset_index = 0;
     for (UInt vertex = 0; vertex < 4; vertex++) {
diff --git a/src/World/Generation/ChunkMeshing.hpp b/src/World/Generation/ChunkMeshing.hpp
index 75023f5..7e202ab 100644
--- a/src/World/Generation/ChunkMeshing.hpp
+++ b/src/World/Generation/ChunkMeshing.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "../../GFX/Mesh.hpp"
+#include "../../GFX/Util/MeshBuilder.hpp"
 #include "../Chunk.hpp"
 
 namespace MC::World::Generation::ChunkMeshing {
@@ -15,13 +16,17 @@ ChunkMesh mesh_chunk(Chunk& chunk, const ChunkNeighbors& neighbors);
 
 namespace Detail {
 
+using Vertex = Vector<3, F32>;
+using Normal = Vector<3, F32>;
+using TexCoord = Vector<2, F32>;
+using AO = F32;
+
+template <typename T>
+using Face = std::array<T, 4>;
+
 template <typename Decisions>
 GFX::Mesh create_mesh(Chunk& chunk, const ChunkNeighbors& neighbors) {
-    std::vector<Vector<3, F32>> positions{};
-    std::vector<Vector<3, F32>> normals{};
-    std::vector<Vector<2, F32>> tex_coords{};
-    std::vector<F32> ambient_occlusion_values{};
-    std::vector<U32> indices{};
+    GFX::Util::MeshBuilder<Normal, TexCoord, AO> builder;
 
     for (Int x = 0; x < Chunk::Width; x++) {
         for (Int y = 0; y < Chunk::Height; y++) {
@@ -34,35 +39,27 @@ GFX::Mesh create_mesh(Chunk& chunk, const ChunkNeighbors& neighbors) {
                     if (!Decisions::is_face_visible(chunk, neighbors, x, y, z, side))
                         continue;
 
-                    auto side_positions = Decisions::face_positions(side, x, y, z);
-                    auto side_normals = Decisions::face_normals(side);
-                    auto side_tex_coords = Decisions::face_tex_coords(block.type, side);
-                    auto side_ao = Decisions::face_ao_values(chunk, neighbors, x, y, z, side);
-
-                    U32 s = positions.size();
+                    U32 s = builder.vertex_count();
 
-                    positions.insert(positions.end(), side_positions.begin(), side_positions.end());
-                    normals.insert(normals.end(), side_normals.begin(), side_normals.end());
-                    tex_coords.insert(tex_coords.end(), side_tex_coords.begin(), side_tex_coords.end());
-                    ambient_occlusion_values.insert(ambient_occlusion_values.end(), side_ao.begin(), side_ao.end());
-                    indices.insert(indices.end(), {s + 0, s + 1, s + 2, s + 2, s + 3, s + 0 });
+                    builder.positions(Decisions::face_positions(side, x, y, z));
+                    builder.attributes<0>(Decisions::face_normals(side));
+                    builder.attributes<1>(Decisions::face_tex_coords(block.type, side));
+                    builder.attributes<2>(Decisions::face_ao_values(chunk, neighbors, x, y, z, side));
+                    builder.indices(std::array{ s + 0, s + 1, s + 2, s + 2, s + 3, s + 0 });
                 }
             }
         }
     }
 
-    return {
-        {positions, normals, tex_coords, ambient_occlusion_values},
-        indices,
-    };
+    return builder.mesh();
 }
 
 class DefaultMeshDecisions {
 public:
-    static std::array<Vector<3, F32>, 4> face_positions(BlockSide side, U32 x, U32 y, U32 z);
-    static std::array<Vector<2, F32>, 4> face_tex_coords(BlockType type, BlockSide side);
-    static std::array<Vector<3, F32>, 4> face_normals(BlockSide side);
-    static std::array<F32, 4> face_ao_values(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side);
+    static Face<Vertex> face_positions(BlockSide side, U32 x, U32 y, U32 z);
+    static Face<TexCoord> face_tex_coords(BlockType type, BlockSide side);
+    static Face<Normal> face_normals(BlockSide side);
+    static Face<AO> face_ao_values(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side);
 
     static Chunk::BlockData get_block_wrapping(const Chunk& chunk, const ChunkNeighbors& neighbors, Vector<3, I32> pos);
     static Vector<3, I32> get_face_normal(BlockSide side);