乒乓球游戏：C++ GDExtension 实现

src/pingpong_ball.cpp

@@ -0,0 +1,136 @@
+#include "pingpong_ball.h"
+
+#include <godot_cpp/core/class_db.hpp>
+#include <godot_cpp/variant/utility_functions.hpp>
+#include <godot_cpp/classes/engine.hpp>
+#include <godot_cpp/classes/kinematic_collision2d.hpp>
+#include <godot_cpp/classes/node2d.hpp>
+#include <godot_cpp/classes/viewport.hpp>
+#include <godot_cpp/classes/window.hpp>
+#include <godot_cpp/classes/scene_tree.hpp>
+
+using namespace godot;
+
+void PingPongBall::_bind_methods() {
+    // 属性
+    ClassDB::bind_method(D_METHOD("get_speed"), &PingPongBall::get_speed);
+    ClassDB::bind_method(D_METHOD("set_speed", "value"), &PingPongBall::set_speed);
+    ClassDB::add_property("PingPongBall", PropertyInfo(Variant::FLOAT, "speed"), "set_speed", "get_speed");
+
+    // 方法
+    ClassDB::bind_method(D_METHOD("reset"), &PingPongBall::reset);
+
+    // 信号
+    ADD_SIGNAL(MethodInfo("scored", PropertyInfo(Variant::INT, "which")));
+}
+
+PingPongBall::PingPongBall() {
+    speed = 400.0f;
+}
+
+PingPongBall::~PingPongBall() {
+}
+
+void PingPongBall::_ready() {
+    reset();
+}
+
+void PingPongBall::_draw() {
+    // 画一个白色圆形表示球
+    draw_circle(Vector2(0.0f, 0.0f), 12.0f, Color(1.0f, 1.0f, 1.0f));
+}
+
+void PingPongBall::_physics_process(double delta) {
+    queue_redraw();
+    Vector2 velocity = direction * speed * (float)delta;
+
+    Ref<KinematicCollision2D> collision = move_and_collide(velocity);
+
+    if (collision.is_valid()) {
+        // 计算反弹方向
+        Vector2 normal = collision->get_normal();
+        direction = direction.bounce(normal);
+
+        // 根据碰撞法线判断碰撞对象类型
+        // 法线主要水平 → 碰到球拍（左右反弹）
+        // 法线主要垂直 → 碰到上下墙（上下反弹）
+        // 如果法线接近水平且球已经接近左右边界 → 得分
+        Object *collider = collision->get_collider();
+        if (collider) {
+            Node *collider_node = Object::cast_to<Node>(collider);
+            if (collider_node) {
+                StringName node_name = collider_node->get_name();
+                // 判断是不是球拍（球拍名字包含 "Paddle"）
+                if (node_name.find("Paddle") != -1) {
+                    // 碰到球拍，微调角度（根据击中位置）
+                    Node2D *collider_2d = Object::cast_to<Node2D>(collider_node);
+                    if (collider_2d) {
+                        float hit_offset = (get_global_position().y - collider_2d->get_global_position().y) / 60.0f;
+                        hit_offset = CLAMP(hit_offset, -1.0f, 1.0f);
+                        direction.y += hit_offset * 0.5f;
+                        direction = direction.normalized();
+                    }
+                }
+            }
+        }
+
+        // 确保方向始终有效
+        direction = direction.normalized();
+    }
+
+    // 检测是否出界（得分判定）
+    Viewport *viewport = get_viewport();
+    if (viewport) {
+        Vector2 screen_size = viewport->get_visible_rect().size;
+        Vector2 pos = get_global_position();
+
+        if (pos.x < -50.0f) {
+            // 球从左边出界，右边得分
+            emit_signal("scored", 1);
+            reset();
+        } else if (pos.x > screen_size.x + 50.0f) {
+            // 球从右边出界，左边得分
+            emit_signal("scored", 0);
+            reset();
+        }
+
+        // Y 方向边界限制（防止飞出屏幕）
+        if (pos.y < 0.0f) {
+            set_global_position(Vector2(pos.x, 0.0f));
+            direction.y = std::abs(direction.y);
+        } else if (pos.y > screen_size.y) {
+            set_global_position(Vector2(pos.x, screen_size.y));
+            direction.y = -std::abs(direction.y);
+        }
+    }
+}
+
+void PingPongBall::reset() {
+    // 回到屏幕中央
+    Viewport *viewport = get_viewport();
+    if (viewport) {
+        Vector2 screen_size = viewport->get_visible_rect().size;
+        set_global_position(screen_size / 2.0f);
+    } else {
+        set_global_position(Vector2(640.0f, 360.0f));
+    }
+
+    // 随机方向（-45° 到 45° 之间，向左或向右随机）
+    float angle = (UtilityFunctions::randf() - 0.5f) * Math_PI / 2.0f;  // -45° ~ 45°
+    int side = (UtilityFunctions::randf() > 0.5f) ? 1 : -1;
+    direction = Vector2((float)side * std::cos(angle), std::sin(angle)).normalized();
+
+    // 确保水平分量足够（避免球过于垂直）
+    if (std::abs(direction.x) < 0.3f) {
+        direction.x = (direction.x > 0 ? 1.0f : -1.0f) * 0.3f;
+        direction = direction.normalized();
+    }
+}
+
+void PingPongBall::set_speed(float p_speed) {
+    speed = p_speed;
+}
+
+float PingPongBall::get_speed() const {
+    return speed;
+}