Urho3D/Source/Samples/32_Urho2DConstraints/Urho2DConstraints.cpp

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#include <Urho3D/Container/Vector.h>
#include <Urho3D/Core/CoreEvents.h>
#include <Urho3D/Engine/Engine.h>
#include <Urho3D/Graphics/Camera.h>
#include <Urho3D/Graphics/DebugRenderer.h>
#include <Urho3D/Graphics/Graphics.h>
#include <Urho3D/Graphics/Octree.h>
#include <Urho3D/Graphics/Renderer.h>
#include <Urho3D/Graphics/Zone.h>
#include <Urho3D/Input/Input.h>
#include <Urho3D/IO/FileSystem.h>
#include <Urho3D/Resource/ResourceCache.h>
#include <Urho3D/Scene/Scene.h>
#include <Urho3D/Scene/SceneEvents.h>
#include <Urho3D/UI/Font.h>
#include <Urho3D/UI/Text.h>
#include <Urho3D/UI/Text3D.h>
#include <Urho3D/Urho2D/CollisionBox2D.h>
#include <Urho3D/Urho2D/CollisionCircle2D.h>
#include <Urho3D/Urho2D/CollisionEdge2D.h>
#include <Urho3D/Urho2D/CollisionPolygon2D.h>
#include <Urho3D/Urho2D/ConstraintDistance2D.h>
#include <Urho3D/Urho2D/ConstraintFriction2D.h>
#include <Urho3D/Urho2D/ConstraintGear2D.h>
#include <Urho3D/Urho2D/ConstraintMotor2D.h>
#include <Urho3D/Urho2D/ConstraintMouse2D.h>
#include <Urho3D/Urho2D/ConstraintPrismatic2D.h>
#include <Urho3D/Urho2D/ConstraintPulley2D.h>
#include <Urho3D/Urho2D/ConstraintRevolute2D.h>
#include <Urho3D/Urho2D/ConstraintRope2D.h>
#include <Urho3D/Urho2D/ConstraintWeld2D.h>
#include <Urho3D/Urho2D/ConstraintWheel2D.h>
#include <Urho3D/Urho2D/Drawable2D.h>
#include <Urho3D/Urho2D/PhysicsWorld2D.h>
#include <Urho3D/Urho2D/RigidBody2D.h>
#include <Urho3D/Urho2D/Sprite2D.h>
#include <Urho3D/Urho2D/StaticSprite2D.h>

#include "Urho2DConstraints.h"

#include <Urho3D/DebugNew.h>

URHO3D_DEFINE_APPLICATION_MAIN(Urho2DConstraints)

Node* pickedNode;
RigidBody2D* dummyBody;

Urho2DConstraints::Urho2DConstraints(Context* context) :
    Sample(context)
{
}

void Urho2DConstraints::Start()
{
    // Execute base class startup
    Sample::Start();

    // Create the scene content
    CreateScene();

    // Enable OS cursor
    GetSubsystem<Input>()->SetMouseVisible(true);

    // Create the UI content
    CreateInstructions();

    // Hook up to the frame update events
    SubscribeToEvents();

    // Set the mouse mode to use in the sample
    Sample::InitMouseMode(MM_FREE);
}

void Urho2DConstraints::CreateScene()
{
    scene_ = new Scene(context_);
    scene_->CreateComponent<Octree>();
    scene_->CreateComponent<DebugRenderer>();
    auto* physicsWorld = scene_->CreateComponent<PhysicsWorld2D>(); // Create 2D physics world component
    physicsWorld->SetDrawJoint(true); // Display the joints (Note that DrawDebugGeometry() must be set to true to acually draw the joints)
    drawDebug_ = true; // Set DrawDebugGeometry() to true

    // Create camera
    cameraNode_ = scene_->CreateChild("Camera");
    // Set camera's position
    cameraNode_->SetPosition(Vector3(0.0f, 0.0f, 0.0f)); // Note that Z setting is discarded; use camera.zoom instead (see MoveCamera() below for example)

    camera_ = cameraNode_->CreateComponent<Camera>();
    camera_->SetOrthographic(true);

    auto* graphics = GetSubsystem<Graphics>();
    camera_->SetOrthoSize((float)graphics->GetHeight() * PIXEL_SIZE);
    camera_->SetZoom(1.2f * Min((float)graphics->GetWidth() / 1280.0f, (float)graphics->GetHeight() / 800.0f)); // Set zoom according to user's resolution to ensure full visibility (initial zoom (1.2) is set for full visibility at 1280x800 resolution)

    // Set up a viewport to the Renderer subsystem so that the 3D scene can be seen
    SharedPtr<Viewport> viewport(new Viewport(context_, scene_, camera_));
    auto* renderer = GetSubsystem<Renderer>();
    renderer->SetViewport(0, viewport);

    Zone* zone = renderer->GetDefaultZone();
    zone->SetFogColor(Color(0.1f, 0.1f, 0.1f)); // Set background color for the scene

    // Create 4x3 grid
    for (unsigned i = 0; i<5; ++i)
    {
        Node* edgeNode = scene_->CreateChild("VerticalEdge");
        auto* edgeBody = edgeNode->CreateComponent<RigidBody2D>();
        if (!dummyBody)
            dummyBody = edgeBody; // Mark first edge as dummy body (used by mouse pick)
        auto* edgeShape = edgeNode->CreateComponent<CollisionEdge2D>();
        edgeShape->SetVertices(Vector2(i*2.5f -5.0f, -3.0f), Vector2(i*2.5f -5.0f, 3.0f));
        edgeShape->SetFriction(0.5f); // Set friction
    }

    for (unsigned j = 0; j<4; ++j)
    {
        Node* edgeNode = scene_->CreateChild("HorizontalEdge");
        /*RigidBody2D* edgeBody = */edgeNode->CreateComponent<RigidBody2D>();
        auto* edgeShape = edgeNode->CreateComponent<CollisionEdge2D>();
        edgeShape->SetVertices(Vector2(-5.0f, j*2.0f -3.0f), Vector2(5.0f, j*2.0f -3.0f));
        edgeShape->SetFriction(0.5f); // Set friction
    }

    auto* cache = GetSubsystem<ResourceCache>();

    // Create a box (will be cloned later)
    Node* box  = scene_->CreateChild("Box");
    box->SetPosition(Vector3(0.8f, -2.0f, 0.0f));
    auto* boxSprite = box->CreateComponent<StaticSprite2D>();
    boxSprite->SetSprite(cache->GetResource<Sprite2D>("Urho2D/Box.png"));
    auto* boxBody = box->CreateComponent<RigidBody2D>();
    boxBody->SetBodyType(BT_DYNAMIC);
    boxBody->SetLinearDamping(0.0f);
    boxBody->SetAngularDamping(0.0f);
    auto* shape = box->CreateComponent<CollisionBox2D>(); // Create box shape
    shape->SetSize(Vector2(0.32f, 0.32f)); // Set size
    shape->SetDensity(1.0f); // Set shape density (kilograms per meter squared)
    shape->SetFriction(0.5f); // Set friction
    shape->SetRestitution(0.1f); // Set restitution (slight bounce)

    // Create a ball (will be cloned later)
    Node* ball  = scene_->CreateChild("Ball");
    ball->SetPosition(Vector3(1.8f, -2.0f, 0.0f));
    auto* ballSprite = ball->CreateComponent<StaticSprite2D>();
    ballSprite->SetSprite(cache->GetResource<Sprite2D>("Urho2D/Ball.png"));
    auto* ballBody = ball->CreateComponent<RigidBody2D>();
    ballBody->SetBodyType(BT_DYNAMIC);
    ballBody->SetLinearDamping(0.0f);
    ballBody->SetAngularDamping(0.0f);
    auto* ballShape = ball->CreateComponent<CollisionCircle2D>(); // Create circle shape
    ballShape->SetRadius(0.16f); // Set radius
    ballShape->SetDensity(1.0f); // Set shape density (kilograms per meter squared)
    ballShape->SetFriction(0.5f); // Set friction
    ballShape->SetRestitution(0.6f); // Set restitution: make it bounce

    // Create a polygon
    Node* polygon = scene_->CreateChild("Polygon");
    polygon->SetPosition(Vector3(1.6f, -2.0f, 0.0f));
    polygon->SetScale(0.7f);
    auto* polygonSprite = polygon->CreateComponent<StaticSprite2D>();
    polygonSprite->SetSprite(cache->GetResource<Sprite2D>("Urho2D/Aster.png"));
    auto* polygonBody = polygon->CreateComponent<RigidBody2D>();
    polygonBody->SetBodyType(BT_DYNAMIC);
    auto* polygonShape = polygon->CreateComponent<CollisionPolygon2D>();
    // TODO: create from PODVector<Vector2> using SetVertices()
    polygonShape->SetVertexCount(6); // Set number of vertices (mandatory when using SetVertex())
    polygonShape->SetVertex(0, Vector2(-0.8f, -0.3f));
    polygonShape->SetVertex(1, Vector2(0.5f, -0.8f));
    polygonShape->SetVertex(2, Vector2(0.8f, -0.3f));
    polygonShape->SetVertex(3, Vector2(0.8f, 0.5f));
    polygonShape->SetVertex(4, Vector2(0.5f, 0.9f));
    polygonShape->SetVertex(5, Vector2(-0.5f, 0.7f));
    polygonShape->SetDensity(1.0f); // Set shape density (kilograms per meter squared)
    polygonShape->SetFriction(0.3f); // Set friction
    polygonShape->SetRestitution(0.0f); // Set restitution (no bounce)

    // Create a ConstraintDistance2D
    CreateFlag("ConstraintDistance2D", -4.97f, 3.0f); // Display Text3D flag
    Node* boxDistanceNode = box->Clone();
    Node* ballDistanceNode = ball->Clone();
    auto* ballDistanceBody = ballDistanceNode->GetComponent<RigidBody2D>();
    boxDistanceNode->SetPosition(Vector3(-4.5f, 2.0f, 0.0f));
    ballDistanceNode->SetPosition(Vector3(-3.0f, 2.0f, 0.0f));

    auto* constraintDistance = boxDistanceNode->CreateComponent<ConstraintDistance2D>(); // Apply ConstraintDistance2D to box
    constraintDistance->SetOtherBody(ballDistanceBody); // Constrain ball to box
    constraintDistance->SetOwnerBodyAnchor(boxDistanceNode->GetPosition2D());
    constraintDistance->SetOtherBodyAnchor(ballDistanceNode->GetPosition2D());
    // Make the constraint soft (comment to make it rigid, which is its basic behavior)
    constraintDistance->SetFrequencyHz(4.0f);
    constraintDistance->SetDampingRatio(0.5f);

    // Create a ConstraintFriction2D ********** Not functional. From Box2d samples it seems that 2 anchors are required, Urho2D only provides 1, needs investigation ***********
    CreateFlag("ConstraintFriction2D", 0.03f, 1.0f); // Display Text3D flag
    Node* boxFrictionNode = box->Clone();
    Node* ballFrictionNode = ball->Clone();
    boxFrictionNode->SetPosition(Vector3(0.5f, 0.0f, 0.0f));
    ballFrictionNode->SetPosition(Vector3(1.5f, 0.0f, 0.0f));

    auto* constraintFriction = boxFrictionNode->CreateComponent<ConstraintFriction2D>(); // Apply ConstraintDistance2D to box
    constraintFriction->SetOtherBody(ballFrictionNode->GetComponent<RigidBody2D>()); // Constraint ball to box
    //constraintFriction->SetOwnerBodyAnchor(boxNode->GetPosition2D());
    //constraintFriction->SetOtherBodyAnchor(ballNode->GetPosition2D());
    //constraintFriction->SetMaxForce(10.0f); // ballBody.mass * gravity
    //constraintDistance->SetMaxTorque(10.0f); // ballBody.mass * radius * gravity

    // Create a ConstraintGear2D
    CreateFlag("ConstraintGear2D", -4.97f, -1.0f); // Display Text3D flag
    Node* baseNode = box->Clone();
    auto* tempBody = baseNode->GetComponent<RigidBody2D>(); // Get body to make it static
    tempBody->SetBodyType(BT_STATIC);
    baseNode->SetPosition(Vector3(-3.7f, -2.5f, 0.0f));
    Node* ball1Node = ball->Clone();
    ball1Node->SetPosition(Vector3(-4.5f, -2.0f, 0.0f));
    auto* ball1Body = ball1Node->GetComponent<RigidBody2D>();
    Node* ball2Node = ball->Clone();
    ball2Node->SetPosition(Vector3(-3.0f, -2.0f, 0.0f));
    auto* ball2Body = ball2Node->GetComponent<RigidBody2D>();

    auto* gear1 = baseNode->CreateComponent<ConstraintRevolute2D>(); // Apply constraint to baseBox
    gear1->SetOtherBody(ball1Body); // Constrain ball1 to baseBox
    gear1->SetAnchor(ball1Node->GetPosition2D());
    auto* gear2 = baseNode->CreateComponent<ConstraintRevolute2D>(); // Apply constraint to baseBox
    gear2->SetOtherBody(ball2Body); // Constrain ball2 to baseBox
    gear2->SetAnchor(ball2Node->GetPosition2D());

    auto* constraintGear = ball1Node->CreateComponent<ConstraintGear2D>(); // Apply constraint to ball1
    constraintGear->SetOtherBody(ball2Body); // Constrain ball2 to ball1
    constraintGear->SetOwnerConstraint(gear1);
    constraintGear->SetOtherConstraint(gear2);
    constraintGear->SetRatio(1.0f);

    ball1Body->ApplyAngularImpulse(0.015f, true); // Animate

    // Create a vehicle from a compound of 2 ConstraintWheel2Ds
    CreateFlag("ConstraintWheel2Ds compound", -2.45f, -1.0f); // Display Text3D flag
    Node* car = box->Clone();
    car->SetScale(Vector3(4.0f, 1.0f, 0.0f));
    car->SetPosition(Vector3(-1.2f, -2.3f, 0.0f));
    auto* tempSprite = car->GetComponent<StaticSprite2D>(); // Get car Sprite in order to draw it on top
    tempSprite->SetOrderInLayer(0); // Draw car on top of the wheels (set to -1 to draw below)
    Node* ball1WheelNode = ball->Clone();
    ball1WheelNode->SetPosition(Vector3(-1.6f, -2.5f, 0.0f));
    Node* ball2WheelNode = ball->Clone();
    ball2WheelNode->SetPosition(Vector3(-0.8f, -2.5f, 0.0f));

    auto* wheel1 = car->CreateComponent<ConstraintWheel2D>();
    wheel1->SetOtherBody(ball1WheelNode->GetComponent<RigidBody2D>());
    wheel1->SetAnchor(ball1WheelNode->GetPosition2D());
    wheel1->SetAxis(Vector2(0.0f, 1.0f));
    wheel1->SetMaxMotorTorque(20.0f);
    wheel1->SetFrequencyHz(4.0f);
    wheel1->SetDampingRatio(0.4f);

    auto* wheel2 = car->CreateComponent<ConstraintWheel2D>();
    wheel2->SetOtherBody(ball2WheelNode->GetComponent<RigidBody2D>());
    wheel2->SetAnchor(ball2WheelNode->GetPosition2D());
    wheel2->SetAxis(Vector2(0.0f, 1.0f));
    wheel2->SetMaxMotorTorque(10.0f);
    wheel2->SetFrequencyHz(4.0f);
    wheel2->SetDampingRatio(0.4f);

    // ConstraintMotor2D
    CreateFlag("ConstraintMotor2D", 2.53f, -1.0f); // Display Text3D flag
    Node* boxMotorNode = box->Clone();
    tempBody = boxMotorNode->GetComponent<RigidBody2D>(); // Get body to make it static
    tempBody->SetBodyType(BT_STATIC);
    Node* ballMotorNode = ball->Clone();
    boxMotorNode->SetPosition(Vector3(3.8f, -2.1f, 0.0f));
    ballMotorNode->SetPosition(Vector3(3.8f, -1.5f, 0.0f));

    auto* constraintMotor = boxMotorNode->CreateComponent<ConstraintMotor2D>();
    constraintMotor->SetOtherBody(ballMotorNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintMotor->SetLinearOffset(Vector2(0.0f, 0.8f)); // Set ballNode position relative to boxNode position = (0,0)
    constraintMotor->SetAngularOffset(0.1f);
    constraintMotor->SetMaxForce(5.0f);
    constraintMotor->SetMaxTorque(10.0f);
    constraintMotor->SetCorrectionFactor(1.0f);
    constraintMotor->SetCollideConnected(true); // doesn't work

    // ConstraintMouse2D is demonstrated in HandleMouseButtonDown() function. It is used to "grasp" the sprites with the mouse.
    CreateFlag("ConstraintMouse2D", 0.03f, -1.0f); // Display Text3D flag

    // Create a ConstraintPrismatic2D
    CreateFlag("ConstraintPrismatic2D", 2.53f, 3.0f); // Display Text3D flag
    Node* boxPrismaticNode = box->Clone();
    tempBody = boxPrismaticNode->GetComponent<RigidBody2D>(); // Get body to make it static
    tempBody->SetBodyType(BT_STATIC);
    Node* ballPrismaticNode = ball->Clone();
    boxPrismaticNode->SetPosition(Vector3(3.3f, 2.5f, 0.0f));
    ballPrismaticNode->SetPosition(Vector3(4.3f, 2.0f, 0.0f));

    auto* constraintPrismatic = boxPrismaticNode->CreateComponent<ConstraintPrismatic2D>();
    constraintPrismatic->SetOtherBody(ballPrismaticNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintPrismatic->SetAxis(Vector2(1.0f, 1.0f)); // Slide from [0,0] to [1,1]
    constraintPrismatic->SetAnchor(Vector2(4.0f, 2.0f));
    constraintPrismatic->SetLowerTranslation(-1.0f);
    constraintPrismatic->SetUpperTranslation(0.5f);
    constraintPrismatic->SetEnableLimit(true);
    constraintPrismatic->SetMaxMotorForce(1.0f);
    constraintPrismatic->SetMotorSpeed(0.0f);

    // ConstraintPulley2D
    CreateFlag("ConstraintPulley2D", 0.03f, 3.0f); // Display Text3D flag
    Node* boxPulleyNode = box->Clone();
    Node* ballPulleyNode = ball->Clone();
    boxPulleyNode->SetPosition(Vector3(0.5f, 2.0f, 0.0f));
    ballPulleyNode->SetPosition(Vector3(2.0f, 2.0f, 0.0f));

    auto* constraintPulley = boxPulleyNode->CreateComponent<ConstraintPulley2D>(); // Apply constraint to box
    constraintPulley->SetOtherBody(ballPulleyNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintPulley->SetOwnerBodyAnchor(boxPulleyNode->GetPosition2D());
    constraintPulley->SetOtherBodyAnchor(ballPulleyNode->GetPosition2D());
    constraintPulley->SetOwnerBodyGroundAnchor(boxPulleyNode->GetPosition2D() + Vector2(0.0f, 1.0f));
    constraintPulley->SetOtherBodyGroundAnchor(ballPulleyNode->GetPosition2D() + Vector2(0.0f, 1.0f));
    constraintPulley->SetRatio(1.0); // Weight ratio between ownerBody and otherBody

    // Create a ConstraintRevolute2D
    CreateFlag("ConstraintRevolute2D", -2.45f, 3.0f); // Display Text3D flag
    Node* boxRevoluteNode = box->Clone();
    tempBody = boxRevoluteNode->GetComponent<RigidBody2D>(); // Get body to make it static
    tempBody->SetBodyType(BT_STATIC);
    Node* ballRevoluteNode = ball->Clone();
    boxRevoluteNode->SetPosition(Vector3(-2.0f, 1.5f, 0.0f));
    ballRevoluteNode->SetPosition(Vector3(-1.0f, 2.0f, 0.0f));

    auto* constraintRevolute = boxRevoluteNode->CreateComponent<ConstraintRevolute2D>(); // Apply constraint to box
    constraintRevolute->SetOtherBody(ballRevoluteNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintRevolute->SetAnchor(Vector2(-1.0f, 1.5f));
    constraintRevolute->SetLowerAngle(-1.0f); // In radians
    constraintRevolute->SetUpperAngle(0.5f); // In radians
    constraintRevolute->SetEnableLimit(true);
    constraintRevolute->SetMaxMotorTorque(10.0f);
    constraintRevolute->SetMotorSpeed(0.0f);
    constraintRevolute->SetEnableMotor(true);

    // Create a ConstraintRope2D
    CreateFlag("ConstraintRope2D", -4.97f, 1.0f); // Display Text3D flag
    Node* boxRopeNode = box->Clone();
    tempBody = boxRopeNode->GetComponent<RigidBody2D>();
    tempBody->SetBodyType(BT_STATIC);
    Node* ballRopeNode = ball->Clone();
    boxRopeNode->SetPosition(Vector3(-3.7f, 0.7f, 0.0f));
    ballRopeNode->SetPosition(Vector3(-4.5f, 0.0f, 0.0f));

    auto* constraintRope = boxRopeNode->CreateComponent<ConstraintRope2D>();
    constraintRope->SetOtherBody(ballRopeNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintRope->SetOwnerBodyAnchor(Vector2(0.0f, -0.5f)); // Offset from box (OwnerBody) : the rope is rigid from OwnerBody center to this ownerBodyAnchor
    constraintRope->SetMaxLength(0.9f); // Rope length
    constraintRope->SetCollideConnected(true);

    // Create a ConstraintWeld2D
    CreateFlag("ConstraintWeld2D", -2.45f, 1.0f); // Display Text3D flag
    Node* boxWeldNode = box->Clone();
    Node* ballWeldNode = ball->Clone();
    boxWeldNode->SetPosition(Vector3(-0.5f, 0.0f, 0.0f));
    ballWeldNode->SetPosition(Vector3(-2.0f, 0.0f, 0.0f));

    auto* constraintWeld = boxWeldNode->CreateComponent<ConstraintWeld2D>();
    constraintWeld->SetOtherBody(ballWeldNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintWeld->SetAnchor(boxWeldNode->GetPosition2D());
    constraintWeld->SetFrequencyHz(4.0f);
    constraintWeld->SetDampingRatio(0.5f);

    // Create a ConstraintWheel2D
    CreateFlag("ConstraintWheel2D",  2.53f, 1.0f); // Display Text3D flag
    Node* boxWheelNode = box->Clone();
    Node* ballWheelNode = ball->Clone();
    boxWheelNode->SetPosition(Vector3(3.8f, 0.0f, 0.0f));
    ballWheelNode->SetPosition(Vector3(3.8f, 0.9f, 0.0f));

    auto* constraintWheel = boxWheelNode->CreateComponent<ConstraintWheel2D>();
    constraintWheel->SetOtherBody(ballWheelNode->GetComponent<RigidBody2D>()); // Constrain ball to box
    constraintWheel->SetAnchor(ballWheelNode->GetPosition2D());
    constraintWheel->SetAxis(Vector2(0.0f, 1.0f));
    constraintWheel->SetEnableMotor(true);
    constraintWheel->SetMaxMotorTorque(1.0f);
    constraintWheel->SetMotorSpeed(0.0f);
    constraintWheel->SetFrequencyHz(4.0f);
    constraintWheel->SetDampingRatio(0.5f);
    constraintWheel->SetCollideConnected(true); // doesn't work
}

void Urho2DConstraints::CreateFlag(const String& text, float x, float y) // Used to create Tex3D flags
{
    Node* flagNode = scene_->CreateChild("Flag");
    flagNode->SetPosition(Vector3(x, y, 0.0f));
    auto* flag3D = flagNode->CreateComponent<Text3D>(); // We use Text3D in order to make the text affected by zoom (so that it sticks to 2D)
    flag3D->SetText(text);
    auto* cache = GetSubsystem<ResourceCache>();
    flag3D->SetFont(cache->GetResource<Font>("Fonts/Anonymous Pro.ttf"), 15);
}

void Urho2DConstraints::CreateInstructions()
{
    auto* cache = GetSubsystem<ResourceCache>();
    auto* ui = GetSubsystem<UI>();

    // Construct new Text object, set string to display and font to use
    auto* instructionText = ui->GetRoot()->CreateChild<Text>();
    instructionText->SetText("Use WASD keys and mouse to move, Use PageUp PageDown to zoom.\n Space to toggle debug geometry and joints - F5 to save the scene.");
    instructionText->SetFont(cache->GetResource<Font>("Fonts/Anonymous Pro.ttf"), 15);
    instructionText->SetTextAlignment(HA_CENTER); // Center rows in relation to each other

    // Position the text relative to the screen center
    instructionText->SetHorizontalAlignment(HA_CENTER);
    instructionText->SetVerticalAlignment(VA_CENTER);
    instructionText->SetPosition(0, ui->GetRoot()->GetHeight() / 4);
}

void Urho2DConstraints::MoveCamera(float timeStep)
{
    // Do not move if the UI has a focused element (the console)
    if (GetSubsystem<UI>()->GetFocusElement())
        return;

    auto* input = GetSubsystem<Input>();

    // Movement speed as world units per second
    const float MOVE_SPEED = 4.0f;

    // Read WASD keys and move the camera scene node to the corresponding direction if they are pressed
    if (input->GetKeyDown(KEY_W))
        cameraNode_->Translate(Vector3::UP * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_S))
        cameraNode_->Translate(Vector3::DOWN * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_A))
        cameraNode_->Translate(Vector3::LEFT * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_D))
        cameraNode_->Translate(Vector3::RIGHT * MOVE_SPEED * timeStep);

    if (input->GetKeyDown(KEY_PAGEUP))
        camera_->SetZoom(camera_->GetZoom() * 1.01f);

    if (input->GetKeyDown(KEY_PAGEDOWN))
        camera_->SetZoom(camera_->GetZoom() * 0.99f);
}

void Urho2DConstraints::SubscribeToEvents()
{
    // Subscribe HandleUpdate() function for processing update events
    SubscribeToEvent(E_UPDATE, URHO3D_HANDLER(Urho2DConstraints, HandleUpdate));

    // Subscribe HandlePostRenderUpdate() function for processing the post-render update event, during which we request debug geometry
    SubscribeToEvent(E_POSTRENDERUPDATE, URHO3D_HANDLER(Urho2DConstraints, HandlePostRenderUpdate));

    // Subscribe to mouse click
    SubscribeToEvent(E_MOUSEBUTTONDOWN, URHO3D_HANDLER(Urho2DConstraints, HandleMouseButtonDown));

    // Unsubscribe the SceneUpdate event from base class to prevent camera pitch and yaw in 2D sample
    UnsubscribeFromEvent(E_SCENEUPDATE);

    if (touchEnabled_)
        SubscribeToEvent(E_TOUCHBEGIN, URHO3D_HANDLER(Urho2DConstraints, HandleTouchBegin3));
}

void Urho2DConstraints::HandleUpdate(StringHash eventType, VariantMap& eventData)
{
    using namespace Update;

    // Take the frame time step, which is stored as a float
    float timeStep = eventData[P_TIMESTEP].GetFloat();

    // Move the camera, scale movement with time step
    MoveCamera(timeStep);

    auto* input = GetSubsystem<Input>();

    // Toggle physics debug geometry with space
    if (input->GetKeyPress(KEY_SPACE))
        drawDebug_ = !drawDebug_;

    // Save scene
    if (input->GetKeyPress(KEY_F5))
    {
        File saveFile(context_, GetSubsystem<FileSystem>()->GetProgramDir() + "Data/Scenes/Constraints.xml", FILE_WRITE);
        scene_->SaveXML(saveFile);
    }
}

void Urho2DConstraints::HandlePostRenderUpdate(StringHash eventType, VariantMap& eventData)
{
    auto* physicsWorld = scene_->GetComponent<PhysicsWorld2D>();
    if (drawDebug_) physicsWorld->DrawDebugGeometry();
}

void Urho2DConstraints::HandleMouseButtonDown(StringHash eventType, VariantMap& eventData)
{
    auto* input = GetSubsystem<Input>();
    auto* physicsWorld = scene_->GetComponent<PhysicsWorld2D>();
    RigidBody2D* rigidBody = physicsWorld->GetRigidBody(input->GetMousePosition().x_, input->GetMousePosition().y_); // Raycast for RigidBody2Ds to pick
    if (rigidBody)
    {
        pickedNode = rigidBody->GetNode();
        //log.Info(pickedNode.name);
        auto* staticSprite = pickedNode->GetComponent<StaticSprite2D>();
        staticSprite->SetColor(Color(1.0f, 0.0f, 0.0f, 1.0f)); // Temporary modify color of the picked sprite

        // Create a ConstraintMouse2D - Temporary apply this constraint to the pickedNode to allow grasping and moving with the mouse
        auto* constraintMouse = pickedNode->CreateComponent<ConstraintMouse2D>();
        constraintMouse->SetTarget(GetMousePositionXY());
        constraintMouse->SetMaxForce(1000 * rigidBody->GetMass());
        constraintMouse->SetCollideConnected(true);
        constraintMouse->SetOtherBody(dummyBody);  // Use dummy body instead of rigidBody. It's better to create a dummy body automatically in ConstraintMouse2D
    }
    SubscribeToEvent(E_MOUSEMOVE, URHO3D_HANDLER(Urho2DConstraints, HandleMouseMove));
    SubscribeToEvent(E_MOUSEBUTTONUP, URHO3D_HANDLER(Urho2DConstraints, HandleMouseButtonUp));
}

void Urho2DConstraints::HandleMouseButtonUp(StringHash eventType, VariantMap& eventData)
{
    if (pickedNode)
    {
        auto* staticSprite = pickedNode->GetComponent<StaticSprite2D>();
        staticSprite->SetColor(Color(1.0f, 1.0f, 1.0f, 1.0f)); // Restore picked sprite color

        pickedNode->RemoveComponent<ConstraintMouse2D>(); // Remove temporary constraint
        pickedNode = nullptr;
    }
    UnsubscribeFromEvent(E_MOUSEMOVE);
    UnsubscribeFromEvent(E_MOUSEBUTTONUP);
}

Vector2 Urho2DConstraints::GetMousePositionXY()
{
    auto* input = GetSubsystem<Input>();
    auto* graphics = GetSubsystem<Graphics>();
    Vector3 screenPoint = Vector3((float)input->GetMousePosition().x_ / graphics->GetWidth(), (float)input->GetMousePosition().y_ / graphics->GetHeight(), 0.0f);
    Vector3 worldPoint = camera_->ScreenToWorldPoint(screenPoint);
    return Vector2(worldPoint.x_, worldPoint.y_);
}

void Urho2DConstraints::HandleMouseMove(StringHash eventType, VariantMap& eventData)
{
    if (pickedNode)
    {
        auto* constraintMouse = pickedNode->GetComponent<ConstraintMouse2D>();
        constraintMouse->SetTarget(GetMousePositionXY());
    }
}

void Urho2DConstraints::HandleTouchBegin3(StringHash eventType, VariantMap& eventData)
{
    auto* graphics = GetSubsystem<Graphics>();
    auto* physicsWorld = scene_->GetComponent<PhysicsWorld2D>();
    using namespace TouchBegin;
    RigidBody2D* rigidBody = physicsWorld->GetRigidBody(eventData[P_X].GetInt(), eventData[P_Y].GetInt()); // Raycast for RigidBody2Ds to pick
    if (rigidBody)
    {
        pickedNode = rigidBody->GetNode();
        auto* staticSprite = pickedNode->GetComponent<StaticSprite2D>();
        staticSprite->SetColor(Color(1.0f, 0.0f, 0.0f, 1.0f)); // Temporary modify color of the picked sprite
        auto* rigidBody = pickedNode->GetComponent<RigidBody2D>();

        // Create a ConstraintMouse2D - Temporary apply this constraint to the pickedNode to allow grasping and moving with touch
        auto* constraintMouse = pickedNode->CreateComponent<ConstraintMouse2D>();
        Vector3 pos = camera_->ScreenToWorldPoint(Vector3((float)eventData[P_X].GetInt() / graphics->GetWidth(), (float)eventData[P_Y].GetInt() / graphics->GetHeight(), 0.0f));
        constraintMouse->SetTarget(Vector2(pos.x_, pos.y_));
        constraintMouse->SetMaxForce(1000 * rigidBody->GetMass());
        constraintMouse->SetCollideConnected(true);
        constraintMouse->SetOtherBody(dummyBody);  // Use dummy body instead of rigidBody. It's better to create a dummy body automatically in ConstraintMouse2D
        constraintMouse->SetDampingRatio(0);
    }
    SubscribeToEvent(E_TOUCHMOVE, URHO3D_HANDLER(Urho2DConstraints, HandleTouchMove3));
    SubscribeToEvent(E_TOUCHEND, URHO3D_HANDLER(Urho2DConstraints, HandleTouchEnd3));
}

void Urho2DConstraints::HandleTouchMove3(StringHash eventType, VariantMap& eventData)
{
    if (pickedNode)
    {
        auto* graphics = GetSubsystem<Graphics>();
        auto* constraintMouse = pickedNode->GetComponent<ConstraintMouse2D>();
        using namespace TouchMove;
        Vector3 pos = camera_->ScreenToWorldPoint(Vector3(float(eventData[P_X].GetInt()) / graphics->GetWidth(), float(eventData[P_Y].GetInt()) / graphics->GetHeight(), 0.0f));
        constraintMouse->SetTarget(Vector2(pos.x_, pos.y_));
    }
}

void Urho2DConstraints::HandleTouchEnd3(StringHash eventType, VariantMap& eventData)
{
    if (pickedNode)
    {
        auto* staticSprite = pickedNode->GetComponent<StaticSprite2D>();
        staticSprite->SetColor(Color(1.0f, 1.0f, 1.0f, 1.0f)); // Restore picked sprite color

        pickedNode->RemoveComponent<ConstraintMouse2D>(); // Remove temporary constraint
        pickedNode = nullptr;
    }
    UnsubscribeFromEvent(E_TOUCHMOVE);
    UnsubscribeFromEvent(E_TOUCHEND);
}