Component+Scene+System: Implement parent-child transform components

README.org

@@ -48,3 +48,5 @@ $ cmake .. && make
 - [[https://www.glfw.org/docs/latest/build_guide.html#build_link_cmake_source][Build GLFW using CMake]]
 - [[https://learnopengl.com][Learn OpenGL]]
 - [[https://www.youtube.com/playlist?list=PLlrATfBNZ98dC-V-N3m0Go4deliWHPFwT][Game Engine]] by The Cherno
+- [[https://www.youtube.com/watch?v=mnIQEQoHHCU][OpenGL 3D Game Tutorial 32: Font Rendering]]
+- [[https://youtu.be/d8cfgcJR9Tk][OpenGL 3D Game Tutorial 33: Distance Field Text Rendering]]

assets/scene/scene1.json

@@ -44,14 +44,44 @@
 			"id": { "id": 3424242 },
 			"tag": { "tag": "Quad 3" },
 			"transform" : {
-				"translate": [ 2.2, 0.0, 0.0 ],
-				"rotate": [ 0.0, 0.0, 0.0 ],
+				"translate": [ 2.2, 1.0, 0.0 ],
+				"rotate": [ 0.0, 0.0, -20.0 ],
 				"scale": [ 1.0, 1.0, 1.0 ]
 			},
 			"sprite": {
 				"color": [ 1.0, 1.0, 1.0, 1.0 ],
 				"texture": "assets/gfx/test-inverted.png"
-			}
+			},
+			"children": [
+				{
+					"id": { "id": 4345472 },
+					"tag": { "tag": "Quad 4" },
+					"transform" : {
+						"translate": [ 0.85, 0.0, 0.0 ],
+						"rotate": [ 0.0, 0.0, 0.0 ],
+						"scale": [ 0.5, 0.5, 1.0 ]
+					},
+					"sprite": {
+						"color": [ 1.0, 1.0, 1.0, 1.0 ],
+						"texture": "assets/gfx/test-inverted.png"
+					},
+					"children": [
+						{
+							"id": { "id": 5234723 },
+							"tag": { "tag": "Quad 5" },
+							"transform" : {
+								"translate": [ 1.0, 0.0, 0.0 ],
+								"rotate": [ 0.0, 0.0, -20.0 ],
+								"scale": [ 0.5, 0.5, 1.0 ]
+							},
+							"sprite": {
+								"color": [ 1.0, 1.0, 1.0, 1.0 ],
+								"texture": "assets/gfx/test-inverted.png"
+							}
+						}
+					]
+				}
+			]
 		},
 		{
 			"id": { "id": 675754 },

src/inferno/component/textareacomponent.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022-2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
@@ -18,7 +18,7 @@ namespace Inferno {
 struct TextAreaComponent {
 	std::string content;
 	std::string font;
-	unsigned char fontSize { 0 };
+	unsigned char fontSize { 12 };
 	float lineSpacing { 1.0f };
 	uint32_t width { 0 };
 

src/inferno/component/transformcomponent.h

@@ -1,11 +1,16 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022,2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
 
 #pragma once
 
+#include <cstdint> // uint32_t
+#include <optional>
+
+#include "entt/entity/entity.hpp"      // entt::null
+#include "entt/entity/fwd.hpp"         // entt::entity
 #include "glm/ext/matrix_float4x4.hpp" // glm::mat4
 #include "glm/ext/vector_float3.hpp"   // glm::vec3
 #include "ruc/format/format.h"
@@ -17,6 +22,8 @@ struct TransformComponent {
 	glm::vec3 translate { 0.0f, 0.0f, 0.0f };
 	glm::vec3 rotate { 0.0f, 0.0f, 0.0f };
 	glm::vec3 scale { 1.0f, 1.0f, 1.0f };
+	entt::entity parent { entt::null };
+
 	glm::mat4 transform { 1.0f }; // Identity matrix
 };
 

src/inferno/scene/scene.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022-2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
@@ -8,6 +8,7 @@
 #include <cstdint> // uint32_t
 #include <limits>  // std::numeric_limits
 
+#include "entt/entity/entity.hpp" // ent::entity
 #include "ruc/file.h"
 #include "ruc/format/log.h"
 #include "ruc/json/json.h"
@@ -62,54 +63,7 @@ void Scene::initialize()
 		VERIFY(entityJson.type() == ruc::Json::Type::Array);
 		const auto& entities = entityJson.asArray();
 		for (size_t i = 0; i < entities.size(); ++i) {
-
-			uint32_t entity = createEntity();
-
-			VERIFY(entities.at(i).type() == ruc::Json::Type::Object);
-			const auto& components = entities.at(i);
-
-			// ID is required
-			VERIFY(components.exists("id"), "id not found");
-			auto& id = getComponent<IDComponent>(entity);
-			components.at("id").getTo(id);
-
-			if (components.exists("tag")) {
-				auto& tag = getComponent<TagComponent>(entity);
-				components.at("tag").getTo(tag);
-			}
-			if (components.exists("transform")) {
-				auto& transform = getComponent<TransformComponent>(entity);
-				components.at("transform").getTo(transform);
-			}
-			if (components.exists("camera")) {
-				auto& camera = addComponent<CameraComponent>(entity);
-				components.at("camera").getTo(camera);
-			}
-			if (components.exists("lua-scripts")) {
-				VERIFY(components.at("lua-scripts").type() == ruc::Json::Type::Array);
-				const auto& scripts = components.at("lua-scripts").asArray();
-				for (size_t j = 0; j < scripts.size(); ++j) {
-					auto& script = addComponent<LuaScriptComponent>(entity);
-					scripts.at(j).getTo(script);
-				}
-			}
-			if (components.exists("native-scripts")) {
-				VERIFY(components.at("native-scripts").type() == ruc::Json::Type::Array);
-				const auto& scripts = components.at("native-scripts").asArray();
-				for (size_t j = 0; j < scripts.size(); ++j) {
-					auto& script = addComponent<NativeScriptComponent>(entity);
-					scripts.at(j).getTo(script);
-					script.bind();
-				}
-			}
-			if (components.exists("sprite")) {
-				auto& sprite = addComponent<SpriteComponent>(entity);
-				components.at("sprite").getTo(sprite);
-			}
-			if (components.exists("text")) {
-				auto& text = addComponent<TextAreaComponent>(entity);
-				components.at("text").getTo(text);
-			}
+			loadEntity(entities.at(i));
 		}
 	}
 
@@ -138,6 +92,8 @@ void Scene::destroy()
 	TransformSystem::destroy();
 }
 
+// -----------------------------------------
+
 uint32_t Scene::createEntity(const std::string& name)
 {
 	return createEntityWithUID(UID(), name);
@@ -150,6 +106,68 @@ uint32_t Scene::createEntityWithUID(UID id, const std::string& name)
 	addComponent<TagComponent>(entity, name.empty() ? "Unnamed Entity" : name);
 	addComponent<TransformComponent>(entity);
 
+	TransformSystem::the().add(entity);
+
+	return entity;
+}
+
+uint32_t Scene::loadEntity(ruc::Json components, uint32_t parentEntity)
+{
+	VERIFY(components.type() == ruc::Json::Type::Object);
+
+	uint32_t entity = createEntity();
+
+	// At minimum, ID is required
+	VERIFY(components.exists("id"), "id not found");
+	auto& id = getComponent<IDComponent>(entity);
+	components.at("id").getTo(id);
+
+	if (components.exists("tag")) {
+		auto& tag = getComponent<TagComponent>(entity);
+		components.at("tag").getTo(tag);
+	}
+	if (components.exists("transform")) {
+		auto& transform = getComponent<TransformComponent>(entity);
+		components.at("transform").getTo(transform);
+		transform.parent = static_cast<entt::entity>(parentEntity);
+	}
+	if (components.exists("camera")) {
+		auto& camera = addComponent<CameraComponent>(entity);
+		components.at("camera").getTo(camera);
+	}
+	if (components.exists("lua-scripts")) {
+		VERIFY(components.at("lua-scripts").type() == ruc::Json::Type::Array);
+		const auto& scripts = components.at("lua-scripts").asArray();
+		for (size_t i = 0; i < scripts.size(); ++i) {
+			auto& script = addComponent<LuaScriptComponent>(entity);
+			scripts.at(i).getTo(script);
+		}
+	}
+	if (components.exists("native-scripts")) {
+		VERIFY(components.at("native-scripts").type() == ruc::Json::Type::Array);
+		const auto& scripts = components.at("native-scripts").asArray();
+		for (size_t i = 0; i < scripts.size(); ++i) {
+			auto& script = addComponent<NativeScriptComponent>(entity);
+			scripts.at(i).getTo(script);
+			script.bind();
+		}
+	}
+	if (components.exists("sprite")) {
+		auto& sprite = addComponent<SpriteComponent>(entity);
+		components.at("sprite").getTo(sprite);
+	}
+	if (components.exists("text")) {
+		auto& text = addComponent<TextAreaComponent>(entity);
+		components.at("text").getTo(text);
+	}
+	if (components.exists("children")) {
+		VERIFY(components.at("children").type() == ruc::Json::Type::Array);
+		const auto& children = components.at("children").asArray();
+		for (size_t i = 0; i < children.size(); ++i) {
+			loadEntity(components.at("children")[i], entity);
+		}
+	}
+
 	return entity;
 }
 
@@ -172,6 +190,8 @@ void Scene::destroyEntity(uint32_t entity)
 	m_registry->destroy(entt::entity { entity });
 }
 
+// -----------------------------------------
+
 glm::mat4 Scene::cameraProjectionView()
 {
 	return CameraSystem::the().projectionView();

src/inferno/scene/scene.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022,2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
@@ -31,6 +31,7 @@ public:
 
 	uint32_t createEntity(const std::string& name = "");
 	uint32_t createEntityWithUID(UID id, const std::string& name = "");
+	uint32_t loadEntity(ruc::Json components, uint32_t parentEntity = entt::null);
 	uint32_t findEntity(std::string_view name);
 	void destroyEntity(uint32_t entity);
 

src/inferno/system/transformsystem.cpp

@@ -1,9 +1,13 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022,2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
 
+#include <algorithm> // std::sort
+#include <cstdint>   // uint32_t
+
+#include "entt/entity/fwd.hpp"          // entt:entity
 #include "glm/ext/matrix_transform.hpp" // glm::translate, glm::rotate, glm::scale, glm::radians
 #include "ruc/format/log.h"
 
@@ -25,7 +29,7 @@ void TransformSystem::update()
 {
 	auto view = m_registry->view<TransformComponent>();
 
-	for (auto entity : view) {
+	for (auto entity : m_hierarchy) {
 
 		auto& component = view.get<TransformComponent>(entity);
 
@@ -42,7 +46,29 @@ void TransformSystem::update()
 
 		// Scale
 		component.transform = glm::scale(component.transform, component.scale);
+
+		// Apply the parent transform to the child transform
+		if (component.parent != entt::null) {
+			auto& parent = view.get<TransformComponent>(component.parent);
+			component.transform = parent.transform * component.transform;
+		}
 	}
 }
 
+void TransformSystem::add(uint32_t entity)
+{
+	m_hierarchy.push_back(static_cast<entt::entity>(entity));
+}
+
+void TransformSystem::sort()
+{
+	std::sort(m_hierarchy.begin(), m_hierarchy.end(),
+	          [](entt::entity a, entt::entity b) {
+				  return (a == entt::null && b == entt::null) ? false
+		                 : (a == entt::null)                  ? true
+		                 : (b == entt::null)                  ? false
+		                                                      : a < b;
+			  });
+}
+
 } // namespace Inferno

src/inferno/system/transformsystem.h

@@ -1,12 +1,14 @@
 /*
- * Copyright (C) 2022 Riyyi
+ * Copyright (C) 2022,2024 Riyyi
  *
  * SPDX-License-Identifier: MIT
  */
 
 #pragma once
 
-#include <memory> // std::shared_ptr
+#include <cstdint> // uint32_t
+#include <memory>  // std::shared_ptr
+#include <vector>
 
 #include "entt/entity/registry.hpp" // entt::entity, entt::registry
 #include "ruc/singleton.h"
@@ -20,9 +22,14 @@ public:
 
 	void update();
 
+	void add(uint32_t entity);
+	void sort();
+
 	void setRegistry(std::shared_ptr<entt::registry> registry) { m_registry = registry; };
 
 private:
+	std::vector<entt::entity> m_hierarchy;
+
 	std::shared_ptr<entt::registry> m_registry;
 };