1 files changed, 255 insertions, 0 deletions
diff --git a/src/client/world/chunk.cc b/src/client/world/chunk.cc
new file mode 100644
index 0000000..99720cb
--- /dev/null
+++ b/src/client/world/chunk.cc
@@ -0,0 +1,255 @@
+#include "client/world/chunk.hh"
+
+namespace client {
+namespace world {
+
+void chunk::render(const float world_x, const float world_z,
+                   const pass& pass) noexcept {
+    const auto make_matrix = [&]() -> glm::mat4 {
+        const auto& proj = client::render::camera::get_proj();
+        const auto& view = client::render::camera::get_view();
+        return glm::translate(proj * view, glm::vec3{world_x, 0, world_z});
+    };
+    static client::render::program program{"res/shaders/face.vs",
+                                           "res/shaders/face.fs"};
+    static const GLint u_matrix = glGetUniformLocation(program, "_u_matrix");
+
+    const GLuint texture [[maybe_unused]] = client::render::get_texture_atlas();
+    glDisable(GL_BLEND);
+    glEnable(GL_DEPTH_TEST);
+    glUseProgram(program);
+    // Our choice of vao depends on which pass we're doing.
+    const auto [vao, elements] = [&pass, this]() -> std::pair<GLuint, GLuint> {
+        if (pass == pass::solid) {
+            return {this->glo->solid_vao, this->glo->solid_elements};
+        }
+        return {this->glo->water_vao, this->glo->water_elements};
+    }();
+    glBindVertexArray(vao);
+
+    glUniformMatrix4fv(u_matrix, 1, GL_FALSE, glm::value_ptr(make_matrix()));
+
+    glDrawArrays(GL_TRIANGLES, 0, elements);
+}
+
+const chunk* chunk::get_neighbour(const chunks_t& chunks,
+                                  shared::math::coords offset) const noexcept {
+    const auto find_it = chunks.find(this->pos + offset);
+    if (find_it == std::end(chunks) || !find_it->second.has_value()) {
+        return nullptr;
+    }
+    return &((*find_it).second.value());
+}
+
+bool chunk::maybe_regenerate_glo(const chunks_t& chunks) noexcept {
+    // We need all surrounding chunks to make our vbo, so early out with false
+    // if we can't do that yet.
+    const auto chunk_forward = this->get_neighbour(chunks, {0, 1});
+    const auto chunk_backward = this->get_neighbour(chunks, {0, -1});
+    const auto chunk_right = this->get_neighbour(chunks, {1, 0});
+    const auto chunk_left = this->get_neighbour(chunks, {-1, 0});
+    if (!chunk_forward || !chunk_left || !chunk_backward || !chunk_right) {
+        return false;
+    }
+
+    // Single-axis-outside-chunk-bounds-allowed block access.
+    const auto get_outside_block = [&](const int x, const int y,
+                                       const int z) -> shared::world::block {
+        if (y < 0 || y >= shared::world::chunk::HEIGHT) {
+            return shared::world::block::type::air;
+        } else if (x >= shared::world::chunk::WIDTH) {
+            return chunk_right->get_block({x - WIDTH, y, z});
+        } else if (x < 0) {
+            return chunk_left->get_block({x + WIDTH, y, z});
+        } else if (z >= shared::world::chunk::WIDTH) {
+            return chunk_forward->get_block({x, y, z - WIDTH});
+        } else if (z < 0) {
+            return chunk_backward->get_block({x, y, z + WIDTH});
+        }
+        return this->get_block({x, y, z});
+    };
+
+    // We fill up two vbos, one for each possible rendering pass.
+    std::vector<block::glvert> solid_data;
+    std::vector<block::glvert> water_data;
+
+    // For all blocks in the chunk, check if its neighbours are air. If they
+    // are, it's possible that we can see the block, so add it to vertices.
+    // We need to read into the neighbours chunk occasionally.
+    for (auto x = 0; x < WIDTH; ++x) {
+        for (auto y = 0; y < HEIGHT; ++y) {
+            for (auto z = 0; z < WIDTH; ++z) {
+                const auto& block = this->get_block({x, y, z});
+                const auto bv = shared::world::block::get_visibility(block);
+
+                if (bv == shared::world::block::visibility::invisible) {
+                    continue;
+                }
+
+                std::vector<block::glvert> glverts;
+                glverts.reserve(6 * 6);
+
+                const auto draw_type = block::get_draw_type(block.type);
+
+                const block::glfaces_t& faces = block::get_glfaces(block.type);
+                if (draw_type == block::draw_type::block) {
+                    const std::array<shared::world::block, 6> around{
+                        get_outside_block(x, y, z + 1),
+                        get_outside_block(x + 1, y, z),
+                        get_outside_block(x, y, z - 1),
+                        get_outside_block(x - 1, y, z),
+                        get_outside_block(x, y + 1, z),
+                        get_outside_block(x, y - 1, z),
+                    };
+
+                    for (auto i = 0ul; i < std::size(faces); ++i) {
+                        const auto ov = block::get_visibility(around[i]);
+                        if (bv == block::visibility::translucent &&
+                            ov == block::visibility::translucent) {
+                            continue;
+                        }
+                        if (ov == block::visibility::solid) {
+                            continue;
+                        }
+
+                        std::ranges::copy(faces[i],
+                                          std::back_inserter(glverts));
+                    }
+                } else if (draw_type == block::draw_type::custom) {
+                    for (const auto& face : faces) {
+                        std::ranges::copy(face, std::back_inserter(glverts));
+                    }
+                }
+
+                // Move the block pos verts to its intended position.
+                // Move the block texture verts to fit in the atlas.
+                const glm::vec3 offset_vec3{x, y, z};
+                const float tex_yoff = static_cast<float>(block.type) - 1.0f;
+                const auto fix_face = [&](auto& face) {
+                    face.vertice += offset_vec3 + 0.5f; // move to origin too
+                    face.texture.z += tex_yoff * 6.0f;
+                    return face;
+                };
+
+                auto& vbo_dest = block.type == shared::world::block::type::water
+                                     ? water_data
+                                     : solid_data;
+                std::ranges::transform(glverts, std::back_inserter(vbo_dest),
+                                       fix_face);
+            }
+        }
+    }
+
+    const auto generate_vbo = [](const auto& data) -> GLuint {
+        GLuint vbo = 0;
+        glGenBuffers(1, &vbo);
+        glBindBuffer(GL_ARRAY_BUFFER, vbo);
+        glBufferData(GL_ARRAY_BUFFER, std::size(data) * sizeof(block::glvert),
+                     std::data(data), GL_STATIC_DRAW);
+        return vbo;
+    };
+    const auto generate_vao = []() -> GLuint {
+        GLuint vao = 0;
+        glGenVertexArrays(1, &vao);
+        glBindVertexArray(vao);
+        // position
+        glEnableVertexAttribArray(0);
+        glVertexAttribPointer(0, sizeof(glm::vec3) / sizeof(float), GL_FLOAT,
+                              GL_FALSE, sizeof(block::glvert), nullptr);
+        // texture
+        glEnableVertexAttribArray(1);
+        glVertexAttribPointer(1, sizeof(glm::vec3) / sizeof(float), GL_FLOAT,
+                              GL_FALSE, sizeof(block::glvert),
+                              reinterpret_cast<void*>(sizeof(glm::vec3)));
+        return vao;
+    };
+    // If we were to emplace glo with these there is no guarantee that each
+    // function will be called in order (at least, for g++ it isn't). Therefore
+    // we need to call them in order first.
+    const auto solid_vbo = generate_vbo(solid_data);
+    const auto solid_vao = generate_vao();
+    const auto water_vbo = generate_vbo(water_data);
+    const auto water_vao = generate_vao();
+    this->glo.emplace(std::size(solid_data), solid_vbo, solid_vao,
+                      std::size(water_data), water_vbo, water_vao);
+    return true;
+}
+
+// http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-testing-boxes/
+static bool box_in_frustum(const std::array<glm::vec3, 8>& points) noexcept {
+    const auto& frustum = client::render::camera::get_frustum();
+
+    for (const auto& plane : frustum) {
+        bool inside = false;
+        bool outside = false;
+
+        for (const auto& point : points) {
+            const float distance = plane.x * point.x + plane.y * point.y +
+                                   plane.z * point.z + plane.w;
+            if (distance < 0.0f) {
+                outside = true;
+            } else {
+                inside = true;
+            }
+
+            if (inside && outside) {
+                break;
+            }
+        }
+
+        if (!inside) {
+            return false;
+        }
+    }
+
+    return true;
+};
+
+static bool is_chunk_visible(const float world_x,
+                             const float world_z) noexcept {
+    const std::array<glm::vec3, 8> box_vertices =
+        [&world_x, &world_z]() -> std::array<glm::vec3, 8> {
+        const float max_world_x = world_x + shared::world::chunk::WIDTH;
+        const float max_world_z = world_z + shared::world::chunk::WIDTH;
+
+        return {glm::vec3{world_x, 0.0f, world_z},
+                {max_world_x, 0.0f, world_z},
+                {world_x, 0.0f, max_world_z},
+                {max_world_x, 0.0f, max_world_z},
+                {world_x, shared::world::chunk::HEIGHT, world_z},
+                {max_world_x, shared::world::chunk::HEIGHT, world_z},
+                {world_x, shared::world::chunk::HEIGHT, max_world_z},
+                {max_world_x, shared::world::chunk::HEIGHT, max_world_z}};
+    }();
+
+    return box_in_frustum(box_vertices);
+}
+
+bool chunk::draw(const chunks_t& chunks, const shared::player& lp,
+                 const pass& pass, const bool skip_regen) noexcept {
+    bool did_regen = false;
+    if (!this->glo.has_value() || this->should_regenerate_vbo) {
+        if (skip_regen || !maybe_regenerate_glo(chunks)) {
+            return false;
+        }
+        this->should_regenerate_vbo = false;
+        did_regen = true;
+    }
+
+    const auto [world_x, world_z] = [&lp, this]() -> std::pair<float, float> {
+        const float offset_x =
+            static_cast<float>(this->pos.x - lp.get_chunk_pos().x);
+        const float offset_z =
+            static_cast<float>(this->pos.z - lp.get_chunk_pos().z);
+        return {offset_x * chunk::WIDTH, offset_z * chunk::WIDTH};
+    }();
+
+    if (is_chunk_visible(world_x, world_z)) {
+        render(world_x, world_z, pass);
+    }
+
+    return did_regen;
+}
+
+} // namespace world
+} // namespace client