Remove Objects/Node from Scene

Hi, I am new for Urho3D and Graphics Engines world. I am trying to learn Urho to create my simulation enviorenment then apply bullet physics.

Today, I tried to remove node from scene. I tried node->Remove() function but it is not worked. Actually it is worked when I call scene_->Clear() function after node->Remove() and create again node with same properties and object created in gray (because of light) and call again node->Remove() and the node is dissappeard.

Yet, it is not I want because I do not want to re-create scene. Therefore I seached a lot and in this topic, I found solution. I used same approach (create vector for deleting nodes and iterate it to delete) and it is worked.

So what is question? The question is why this is worked? I do not understand the reason. Also, I wonder why node->Remove() not work proper for me?

I am not CS guy; thus, I lost sometimes . Maybe this topic is not needed but I want to ask them.

Thanks in advance…

Did the node have any custom component children? Overriding OnNodeSet Or OnSceneSet without calling base function or checking nullptr will crash your program.
What do you have inside the nodes you’re trying to remove?

You shouldn’t need to do anything else.

Looks like problem is somewhere else… Can you show the code?

If node->Remove() is called on the same node that you call node->CreateComponent<StaticModel>(), then it should work…

Thanks for answers,

I had an node that has sphere with static model. So, I don’t have custom component.

Yes, it is :

#include "app.h"

void gApp::Setup()
{
	engineParameters_[EP_FULL_SCREEN] = false;
	engineParameters_[EP_WINDOW_RESIZABLE] = true;
	engineParameters_[EP_WINDOW_WIDTH] = 1280;
	engineParameters_[EP_WINDOW_HEIGHT] = 720;

	InitGlobalHandleFunctions();
}


void gApp::InitGlobalHandleFunctions()
{
	SubscribeToEvent(E_KEYDOWN, URHO3D_HANDLER(gApp, KeyPressed));
	SubscribeToEvent(E_UPDATE, URHO3D_HANDLER(gApp, UpdateFrame));
}


void gApp::Start()
{
	// create resource cache
	ResourceCache* cache = GetSubsystem<ResourceCache>();

	// create scene
	scene_ = new Scene(context_);
	scene_->CreateComponent<Octree>(); // create scene component

	// create ground
	Node* groundNode = scene_->CreateChild("Ground");
	groundNode->SetPosition(Vector3(0, 0, 0));
	groundNode->SetScale(Vector3(50, 3, 50));
	StaticModel* groundObj = groundNode->CreateComponent<StaticModel>();
	groundObj->SetModel(cache->GetResource<Model>("Models/Box.mdl"));

	// create ui style
	auto* uiStyle = cache->GetResource<XMLFile>("UI/DefaultStyle.xml"); // load window style from souce

	uiRoot_ = GetSubsystem<UI>()->GetRoot();
	uiRoot_->SetDefaultStyle(uiStyle);

	// make window
	window_ = new Window(context_);
	window_->SetSize(300,400);
	window_->SetLayout(LM_VERTICAL, 6, IntRect(6, 6, 6, 6));
	window_->SetAlignment(HA_LEFT, VA_TOP);
	window_->SetName("Window");

	// make window title
	auto* windowTitle = new Text(context_);
	windowTitle->SetName("WindowTitle");
	windowTitle->SetText("Debug Console!");

	// make fps text
	fpsText = new Text(context_);
	fpsText->SetName("FpsText");

	// make obj text
	objText = new Text(context_);
	objText->SetName("ObjText");

	// edit window and its childs
	window_->SetStyleAuto();
	window_->AddChild(windowTitle);
	window_->AddChild(fpsText);
	window_->AddChild(objText);
	windowTitle->SetStyleAuto();
	fpsText->SetStyleAuto();
	objText->SetStyleAuto();

	// add window to ui
	uiRoot_->AddChild(window_);


	// We need a camera from which the viewport can render.
	cameraNode_ = scene_->CreateChild("Camera");
	cameraNode_->SetPosition(Vector3(0, 30, -50));
	cameraNode_->Yaw(-0);
	cameraNode_->Pitch(30);
	Camera* camera = cameraNode_->CreateComponent<Camera>();
	camera->SetFarClip(1000);

	// Create a directional light (sun)
	{
		lightNode = scene_->CreateChild();
		lightNode->SetDirection(Vector3::FORWARD);
		lightNode->SetPosition(Vector3(0, 30, -30));
		lightNode->Yaw(0);     // horizontal
		lightNode->Pitch(20);   // vertical
		lightDirection = 1;
		Light* light = lightNode->CreateComponent<Light>();
		light->SetLightType(LIGHT_POINT);
		light->SetBrightness(1.6);
		light->SetRange(150);
		light->SetColor(Color(1.0, 1., 1., 1));
		light->SetCastShadows(true);
	}

	// Now we setup the viewport. Of course, you can have more than one!
	Renderer* renderer = GetSubsystem<Renderer>();
	SharedPtr<Viewport> viewport(new Viewport(context_, scene_, cameraNode_->GetComponent<Camera>()));
	renderer->SetViewport(0, viewport);
}


void gApp::Stop()
{}


void gApp::KeyPressed(StringHash eventType, VariantMap& eventData)
{
	using namespace KeyDown;
	int key = eventData[P_KEY].GetInt();
	if (key == KEY_ESCAPE)
		engine_->Exit();

	if (key == KEY_TAB)    // toggle mouse cursor when pressing tab
	{
		GetSubsystem<Input>()->SetMouseVisible(!GetSubsystem<Input>()->IsMouseVisible());
	}
}


void gApp::UpdateFrame(StringHash eventType, VariantMap& eventData)
{
	float timeStep = eventData[Update::P_TIMESTEP].GetFloat();
	framecount_++;
	time_ += timeStep;
	if (time_ > 0)
	{
		float diffFrame = framecount_ - oldframe_;
		framecount_ = 0;
		oldframe_ = framecount_;
		// update debug console values
		fpsText->SetText("FPS : " + String(diffFrame / timeStep) + " " + String(lightNode->GetPosition().x_));
	}

	// move light
	if (lightNode->GetPosition().x_ < -10 || lightNode->GetPosition().x_ > +10)
		lightDirection *= -1;
	float locX = lightNode->GetPosition().x_ + timeStep*lightDirection;
	lightNode->SetPosition(Vector3(locX , 20, 0));

	// Movement speed as world units per second
	float MOVE_SPEED = 10.0f;
	// Mouse sensitivity as degrees per pixel
	const float MOUSE_SENSITIVITY = 0.1f;

	// Key Inputs
	Input* input = GetSubsystem<Input>();
	if (input->GetKeyDown(KEY_SHIFT))
		MOVE_SPEED *= 10;
	if (input->GetKeyDown(KEY_W))
		cameraNode_->Translate(Vector3(0, 0, 1)*MOVE_SPEED*timeStep);
	if (input->GetKeyDown(KEY_S))
		cameraNode_->Translate(Vector3(0, 0, -1)*MOVE_SPEED*timeStep);
	if (input->GetKeyDown(KEY_A))
		cameraNode_->Translate(Vector3(-1, 0, 0)*MOVE_SPEED*timeStep);
	if (input->GetKeyDown(KEY_D))
		cameraNode_->Translate(Vector3(1, 0, 0)*MOVE_SPEED*timeStep);

	if (input->GetMouseButtonDown(MOUSEB_LEFT))
		SpawnObject();
	if (input->GetMouseButtonDown(MOUSEB_RIGHT))
	{
		DeleteObject();
	}

	// Update POV with Mouse Movement
	if (!GetSubsystem<Input>()->IsMouseVisible())
	{
		// Use this frame's mouse motion to adjust camera node yaw and pitch. Clamp the pitch between -90 and 90 degrees
		IntVector2 mouseMove = input->GetMouseMove();
		float yaw_ = cameraNode_->GetRotation().YawAngle();
		float pitch_ = cameraNode_->GetRotation().PitchAngle();
		yaw_ += MOUSE_SENSITIVITY*mouseMove.x_;
		pitch_ += MOUSE_SENSITIVITY*mouseMove.y_;
		pitch_ = Clamp(pitch_, -90.0f, 90.0f);
		// Reset rotation and set yaw and pitch again
		cameraNode_->SetDirection(Vector3::FORWARD);
		cameraNode_->Yaw(yaw_);
		cameraNode_->Pitch(pitch_);
	}

}


void gApp::SpawnObject()
{
	// Spawn object when left mouse button clicked
	ResourceCache* cache = GetSubsystem<ResourceCache>();
	sphereNode_ = scene_->CreateChild("SmallBox");
	sphereNode_->SetPosition(Vector3(0, 10, 0));
	StaticModel *sphereObject = sphereNode_->CreateComponent<StaticModel>();
	sphereObject->SetModel(cache->GetResource<Model>("Models/Sphere.mdl"));
	sphereObject->SetMaterial(cache->GetResource<Material>("Materials/uvMat.xml"));
	sphereObject->SetCastShadows(true);
	objText->SetText("Object created!");
	vWeakPtrDelete.Push(sphereNode_); // deleter vector store nodes which will be delete
}

void gApp::DeleteObject()
{
	// delete objects which stored deleter vector when right mouse button clicked
	for (auto itr = vWeakPtrDelete.Begin(); itr != vWeakPtrDelete.End(); itr++)
	{
		WeakPtr<Node> node = *itr;

		if (!node || !node->GetParent() || !node->GetScene())
			continue;

		node->Remove();

		objText->SetText("Object removed!");
	}
	vWeakPtrDelete.Clear();
}

This is my arranged code. As I said above actually it is removed but not from scene_. This version of code working but when I used sphereNode_->Remove() instead of DeleteObject() function error occured.

I suspect that your problem was that you didn’t check if sphereNode_ was a valid pointer (i.e. if (sphereNode_) sphereNode_->Remove();), so the second time you called sphereNode_->Remove() the node had already been deleted.

Thank you for answer,

I tried your suggestion. Unfortunately it is not work.

Maybe try an assert(sphereNode_); for testing purposes, to make sure it’s there?

Welcome to the forums, btw.

Hi , Thanks for answer, it is not worked .

Actually I found the problem, problem is when I spawn object, it create more than 1. For example, when I clicked left mouse button, It creates 5 sphere. When I called remove sphereNode_, it removes just one of them.

I understand the problem during applying linear velocity . So, why it creates more than one sphere?

As i see you use GetMouseButtonDown for spawning objects. This function will return true constantly until you release the button so it might run 5 more frames until you release it. Use GetMouseButtonPress This function return true only once until you release the button and press again.

Thank you so much, I did not focus on that. To learn how it works, I dive on samples so i take some parts directly. Anyway this topic can be closed. Thank you everyone