Move camera to world space position of player

src/engine/geometry.c

@@ -9,9 +9,9 @@ Transform identity() {
 	                     .d1 = 0.0f, .d2 = 0.0f, .d3 = 0.0f, .d4 = 1.0f };
 }
 
-void multiply(Transform* transform, Transform by) {
-	GLfloat* a = (GLfloat*) &by;
-	GLfloat* b = (GLfloat*) transform;
+Transform multiply(Transform t1, Transform t2) {
+	GLfloat* a = (GLfloat*) &t1;
+	GLfloat* b = (GLfloat*) &t2;
 
 	for (size_t row = 0; row < 4; ++row) {
 		for (size_t col = 0; col < 4; ++col) {
@@ -22,13 +22,16 @@ void multiply(Transform* transform, Transform by) {
 				+ a[(row * 4) + 3] * b[(3 * 4) + col];
 		}
 	}
+	return t2;
 }
 
 void translate(Transform* transform, Vector3D vec) {
-	multiply(transform, (Transform) { .a1 = 1.0f, .a2 = 0.0f, .a3 = 0.0f, .a4 = vec.x,
-                                      .b1 = 0.0f, .b2 = 1.0f, .b3 = 0.0f, .b4 = vec.y,
-                                      .c1 = 0.0f, .c2 = 0.0f, .c3 = 1.0f, .c4 = vec.z,
-                                      .d1 = 0.0f, .d2 = 0.0f, .d3 = 0.0f, .d4 = 1.0f });
+	*transform = multiply(
+		(Transform) { .a1 = 1.0f, .a2 = 0.0f, .a3 = 0.0f, .a4 = vec.x,
+		              .b1 = 0.0f, .b2 = 1.0f, .b3 = 0.0f, .b4 = vec.y,
+		              .c1 = 0.0f, .c2 = 0.0f, .c3 = 1.0f, .c4 = vec.z,
+		              .d1 = 0.0f, .d2 = 0.0f, .d3 = 0.0f, .d4 = 1.0f },
+		*transform);
 }
 
 Vector3D translationOf(Transform transform) {

src/engine/geometry.h

@@ -20,6 +20,7 @@ struct Transform {
 };
 
 Transform identity();
+Transform multiply(Transform t1, Transform t2);
 void translate(Transform* transform, Vector3D vec);
 Vector3D translationOf(Transform transform);
 

src/engine/render.c

@@ -96,7 +96,7 @@ static void setupCamera() {
 static void moveCameraTo(const Scene* anchor) {
 	glMatrixMode(GL_PROJECTION);
 	// TODO This needs to account for parent nodes as well
-	Vector3D pos = translationOf(anchor->transform);
+	Vector3D pos = translationOf(worldTransform(anchor));
 	glTranslatef(-pos.x, -pos.y, -pos.z);
 }
 

src/engine/scene.c

@@ -24,7 +24,7 @@ void insertChildScene(Scene* scene, Scene* newChild) {
 	}
 	if (newChild->parent) {
 		logError(
-			"Cannot insert scene 0x%p as child of 0x%p, because it is already child of 0x%p",
+			"Cannot insert Scene 0x%p as child of 0x%p, because it is already child of 0x%p",
 			newChild,
 			scene,
 			newChild->parent);
@@ -67,3 +67,18 @@ void reparentScene(Scene* scene, Scene* newParent) {
 
 	insertChildScene(newParent, scene);
 }
+
+Transform worldTransform(const Scene* scene) {
+	if (!scene) {
+		logError("Cannot compute world space Transform of null Scene");
+		return identity();
+	}
+
+	if (scene->parent) {
+		return multiply(scene->transform, worldTransform(scene->parent));
+	}
+	else {
+		return scene->transform;
+	}
+}
+

src/engine/scene.h

@@ -18,5 +18,6 @@ Scene* currentScene;
 Scene* newScene();
 void insertChildScene(Scene* scene, Scene* newChild);
 void reparentScene(Scene* scene, Scene* newParent);
+Transform worldTransform(const Scene* scene);
 
 #endif // SCENE_H_