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Using Manipulators to Transform Objects

Using Manipulators to Transform Objects

After adding an object to the scene in Unigine Editor, you can control object transformations with control devices. But sometimes transformations are supposed to be made at application runtime. For example, when you create your own game with a world editor, where you can place objects in the world and move them around.

This usage example will teach you how to:

Select an object on the screen with the mouse using Intersections.
Use manipulator widgets to modify the object transform matrix.
Switch between different manipulator widgets using the keyboard.

Creating Manipulators to Control Object Transformations#

There are 3 types of manipulator widgets used for object transforming:

Widget Manipulator Translator creates a mover manipulator used to translate objects along three axes with arrows at the end.
Widget Manipulator Rotator creates a rotation manipulator used to rotate objects around three axes in the form of a sphere.
Widget Manipulator Scaler creates a scaling manipulator used to scale objects along three axes in the form of a triangle.

All these manipulators work the same way, each of them visually represents a part of the transformation matrix that you can change by dragging the control elements of the widget. Use the CHANGED callback of the widget to make the selected object follow manipulators transformations.

Source code (C#)

public class Manipulator : Component
{
	// declare object and translator widget manipulator variables
    Unigine.Node obj;
	WidgetManipulator ObjManTranslator;
	
    private void Init()
    {
        // write here code to be called on component initialization
		
		// create a manipulator class instance and add it to the UI
        gui = Gui.Get();
        ObjManTranslator = new WidgetManipulatorTranslator(gui);
        gui.AddChild(ObjManTranslator);
		
		// setting the ApplyTransform method as a callback on changing the widget state
		ObjManTranslator.AddCallback(Gui.CALLBACK_INDEX.CHANGED, ApplyTransform);
    }
	
	// a callback method used to transform an object
	private void ApplyTransform()
	{
		if(obj != null)
			obj.WorldTransform = ObjManTranslator.Transform;
	}
}

Selecting Objects Using Mouse Cursor#

To select an object under the mouse cursor we should cast a ray from the cursor location in the view direction of the camera using the World.GetIntersection() method, that returns an intersected object (if any).

Source code (C#)

private Unigine.Node GetNoteUnderCursor()
{
	WorldIntersection intersection = new WorldIntersection();
	ivec2 mouse = Input.MouseCoord;
	
	// find a point 100 units away in front of the camera
	vec3 p0 = Game.Player.WorldPosition;
	vec3 p1 = p0 + new vec3(Game.Player.GetDirectionFromScreen(mouse.x, mouse.y)) * 100;
	
	// cast a ray, that will detect an object within 100 units in front of the camera and return it
	return World.GetIntersection(p0, p1, 1, intersection);
}

Putting it All Together#

Now let's put it all together and add a keyboard handler to switch the current manipulator. For example, let's use Z, X, C keys to select Translator, Rotator, Scaler Manipulators accordingly. The selected widget will be displayed on the screen where the object is located (i.e. it will have the same transformation).

Create a new C# component — Manipulator. Double-click it in the Asset Browser to edit code in your IDE.
Copy the code below and paste it to your component.
Assign Manipulator to any enabled node in the world and click Play.

Source code (C#)

// Manipulator.cs
public class Manipulator : Component
{
    // WorldIntersection object to store the information about the intersection 
    WorldIntersection intersection = new WorldIntersection();
 
    // Unigine.Object object to gain access to a selected object's transform in Unigine 
    Unigine.Node obj;
 
    // create manipulators for each type of transform(Translating, Scaling, Rotating) 
    WidgetManipulator ObjManTranslator;
    WidgetManipulator ObjManScaler;
    WidgetManipulator ObjManRotator;
	
	// create widget manipulator used to store transformation matrix of an active widget
	WidgetManipulator CurrentObjectManipulator;
    Gui gui;
 
    [Method(Order=2)] private void Init()
    {
        // write here code to be called on component initialization 
        gui = Gui.Get();

		// create widget for each transformation type
        ObjManTranslator = new WidgetManipulatorTranslator(gui);
        ObjManScaler = new WidgetManipulatorScaler(gui);
        ObjManRotator = new WidgetManipulatorRotator(gui);
		
		// set projection for the widgets
        ObjManTranslator.Projection= Game.Player.Camera.Projection;
        ObjManScaler.Projection = Game.Player.Camera.Projection;
        ObjManRotator.Projection = Game.Player.Camera.Projection;

		// add widgets to UI
        gui.AddChild(ObjManTranslator);
        gui.AddChild(ObjManScaler);
        gui.AddChild(ObjManRotator);

        // add a callback for each widget   
        ObjManTranslator.AddCallback(Gui.CALLBACK_INDEX.CHANGED, ApplyTransform);
        ObjManRotator.AddCallback(Gui.CALLBACK_INDEX.CHANGED, ApplyTransform);
        ObjManScaler.AddCallback(Gui.CALLBACK_INDEX.CHANGED, ApplyTransform);


		// hide created widgets
        ObjManScaler.Hidden = true;
        ObjManRotator.Hidden = true;
        ObjManTranslator.Hidden = true;
    }
 
    private void Update()
    {
        // write here code to be called before updating each render frame
         if (!Game.Player)
            return;
	
		// set modelview for each widget manipulator every frame
        ObjManTranslator.Modelview = Game.Player.Camera.Modelview;
        ObjManScaler.Modelview = Game.Player.Camera.Modelview;
        ObjManRotator.Modelview = Game.Player.Camera.Modelview;

        // select an object with right-click
		if (Input.IsMouseButtonDown(Input.MOUSE_BUTTON.RIGHT))
        {
            obj = GetNoteUnderCursor();
        }

		// choose manipulator with Z,X,C keys
		if(obj)
		{
			if(Input.IsKeyDown(Input.KEY.Z))
				SwitchManipulator(ObjManTranslator);
			if(Input.IsKeyDown(Input.KEY.X))
				SwitchManipulator(ObjManRotator);
			if(Input.IsKeyDown(Input.KEY.C))
				SwitchManipulator(ObjManScaler);
            CurrentObjectManipulator.Transform = obj.WorldTransform;
		}
    }
 
    // transform an object
	private void ApplyTransform()
	{
		if(obj != null)
			obj.WorldTransform = CurrentObjectManipulator.Transform;
	}
 
    // find an object under the cursor
    private Unigine.Node GetNoteUnderCursor()
    {
        ivec2 mouse = Input.MouseCoord;

        // find a point 100 units away in front of the camera
        vec3 p0 = Game.Player.WorldPosition;
        vec3 p1 = p0 + new vec3(Game.Player.GetDirectionFromScreen(mouse.x, mouse.y)) * 100;
		
        // cast a ray, that will detect an object within 100 units in front of the camera
        return World.GetIntersection(p0, p1, 1, intersection);
    }

	// relocate chosen manipulator to the position of selected object and make it visible
	void SwitchManipulator(WidgetManipulator CurrentManipulator)
	{
		// relocate a widget and making it visible
		CurrentManipulator.Transform = obj.WorldTransform;
		CurrentManipulator.Hidden = false;
		
		// make other widgets hidden
		CurrentObjectManipulator = CurrentManipulator;
		if(ObjManTranslator != CurrentManipulator)
			ObjManTranslator.Hidden = true;
		if(ObjManRotator != CurrentManipulator)
			ObjManRotator.Hidden = true;
		if(ObjManScaler != CurrentManipulator)
			ObjManScaler.Hidden = true;
	}
}

Last update: 2021-12-13

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Using Manipulators to Transform Objects

In This Article:

See Also#

Creating Manipulators to Control Object Transformations#

Selecting Objects Using Mouse Cursor#

Putting it All Together#