ADD: planet prototype

src/scene/planet/planet_system.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <core/world.h>
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <vector>
+
+class EngineContext;
+class SceneManager;
+struct DrawContext;
+class MeshAsset;
+struct GLTFMaterial;
+
+class PlanetSystem
+{
+public:
+    enum class BodyID : uint8_t
+    {
+        Earth = 0,
+        Moon = 1,
+    };
+
+    struct PlanetBody
+    {
+        std::string name;
+        WorldVec3 center_world{0.0, 0.0, 0.0};
+        double radius_m = 1.0;
+        bool visible = true;
+
+        std::shared_ptr<MeshAsset> mesh;
+        std::shared_ptr<GLTFMaterial> material;
+    };
+
+    void init(EngineContext *context);
+
+    void update_and_emit(const SceneManager &scene, DrawContext &draw_context);
+
+    bool enabled() const { return _enabled; }
+    void set_enabled(bool enabled) { _enabled = enabled; }
+
+    const PlanetBody *get_body(BodyID id) const;
+    PlanetBody *get_body(BodyID id);
+    const std::vector<PlanetBody> &bodies() const { return _bodies; }
+
+private:
+    void ensure_bodies_created();
+
+    EngineContext *_context = nullptr;
+    bool _enabled = true;
+    std::vector<PlanetBody> _bodies;
+};
+