Basic Object Movements

WarningThe scope of applications for UnigineScript is limited to implementing materials-related logic (material expressions, scriptable materials, brush materials). Do not use UnigineScript as a language for application logic, please consider C#/C++ instead, as these APIs are the preferred ones. Availability of new Engine features in UnigineScipt (beyond its scope of applications) is not guaranteed, as the current level of support assumes only fixing critical issues.

Direction Vector#

A direction vector is an important concept of mesh transformation. To move the node forward, you should know where is the forward direction of the mesh. When the mesh is exported from a 3D editor, it saves the information about the forward direction. And when you add the mesh to the Unigine, it will have the same orientation as it had in a 3D editor.


A mesh in Maya	The same mesh in Unigine

On pictures given above, the direction vector has positive Y-direction. To move this mesh forward, you should get the direction of the mesh by using the Y component (the second column) of the world transformation matrix of the mesh.

The point is that content creators and programmers should make an arrangement about the direction vector.

Basic Movements#

Moving Forward#

This section contains different ways of setting the forward movement of the mesh.

In this example, we used the "p" key pressing to move the mesh forward. The direction vector is visualized for clarity.

Source code (UnigineScript)

// define the ObjectMeshStatic mesh, player, and movement speed
ObjectMeshStatic mesh;
float movement_speed = 5.0f;
Player player;

/* 
	the world script init() function
 */
int init() {
	
	// enable visualizer
	engine.visualizer.setEnabled(1);

	// create a camera and add it to the world
	player = new PlayerSpectator();
	player.setPosition(Vec3(4.0f, -3.401f, 1.5f));
	player.setDirection(vec3(0.0f, 1.0f, -0.4f),player.getUp());
	engine.game.setPlayer(player);
	
	// create a mesh by adding a box surface to it
	Mesh mesh_0 = new Mesh();
	mesh_0.addBoxSurface("box_surface", vec3(1.0f));
	// add the mesh to the editor as the ObjectMeshStatic
	mesh = new ObjectMeshStatic(mesh_0);
	// set the mesh position and material
	mesh.setPosition(Vec3(4.0f,0.0f,1.0f));
	mesh.setMaterial("mesh_base", "*");

	// check if the key is pressed and update the state of the specified control
	// you can use both 'p' or ASCII code (112)
	engine.controls.setStateKey(CONTROLS_STATE_AUX_0,'p');

	return 1;
}

/* 
	the world script update() function
*/
int update() {

	// get the frame duration
	float ifps = engine.game.getIFps();

	// get the current world transform matrix of the mesh
	Mat4 transform = mesh.getWorldTransform();

	// get the direction vector of the mesh by using swizzling
	Vec3 direction = transform.m01m11m21;
	
	// render the direction vector for visual clarity
	engine.visualizer.renderDirection(mesh.getWorldPosition(), vec3(direction), vec4(1.0f, 0.0f, 0.0f, 1.0f), 0.1f, 0);
	
	// check if the control key is pressed
	if(engine.controls.getState(CONTROLS_STATE_AUX_0)) {

		// calculate the delta of movement
		Vec3 delta_movement = direction * movement_speed * ifps;

		// set a new position to the mesh
		mesh.setWorldPosition(mesh.getWorldPosition() + delta_movement);
	}

	return 1;
}

Another way of getting the direction vector is by using this command:

Source code (UnigineScript)

Vec3 direction = Vec3(transform.col1);

Another Way of Setting Mesh Position

The new position can be also set by setting the WorldTransform variable. The following examples contain the code from the Update() function of the AppWorldLogic class. The part of controls initialization is the same for this method, the difference is in the Update() function only.

Source code (UnigineScript)

// check if the control key is pressed
if(engine.controls.getState(CONTROLS_STATE_AUX_0)) {

	// calculate the delta of movement
	Vec3 delta_movement = direction * movement_speed * ifps;

	// set a new position to the mesh
	mesh.setWorldTransform(translate(delta_movement) * transform);
}

Or you can change the translation column of the world transformation matrix (see the Matrix Transformations article) to move the mesh:

Source code (UnigineScript)

// check if the control key is pressed
if(engine.controls.getState(CONTROLS_STATE_AUX_0)) {

	// calculate the delta of movement
	Vec3 delta_movement = direction * movement_speed * ifps;

	// set a new position
	// here, you can also use swizzling: transform.m03m13m23 += delta_movement;
	transform.col3 += Vec4(delta_movement,1.0f);
	
	// set a new position to the mesh
	mesh.setWorldTransform(transform);
}

Rotation#

This section contains implementation of the mesh rotation.

You can rotate the mesh in two ways, by changing the transformation matrix represented by the WorldTransform variable (recommended way) or via the SetWorldRotation() function. The following example uses the second one:

Source code (UnigineScript)

// define the ObjectMeshStatic mesh, player, and rotation speed
ObjectMeshStatic mesh;
float rotation_speed = 30.0f;
Player player;

/* 
	the world script init() function
 */
int init() {
	// enable visualizer
	engine.visualizer.setEnabled(1);

	// create a camera and add it to the world
	player = new PlayerSpectator();
	player.setPosition(Vec3(4.0f, -3.401f, 1.5f));
	player.setDirection(vec3(0.0f, 1.0f, -0.4f),player.getUp());
	engine.game.setPlayer(player);
	
	// create a mesh by adding a box surface to it
	Mesh mesh_0 = new Mesh();
	mesh_0.addBoxSurface("box_surface", vec3(1.0f));
	// add the mesh to the editor as the ObjectMeshStatic
	mesh = new ObjectMeshStatic(mesh_0);
	// set the mesh position and material
	mesh.setPosition(Vec3(4.0f,0.0f,1.0f));
	mesh.setMaterial("mesh_base", "*");

	// check if the key is pressed and update the state of the specified control
	// you can use both 'o' or ASCII code (111)
	engine.controls.setStateKey(CONTROLS_STATE_AUX_1,'o');

	return 1;
}

/* 
	the world script update() function
*/
int update() {

	// get the frame duration
	float ifps = engine.game.getIFps();

	// check if the control key is pressed
	if(engine.controls.getState(CONTROLS_STATE_AUX_1)) {
		// set the node rotation along the Z axis assuming node's scale equal to 1
		mesh.setWorldRotation(mesh.getWorldRotation() * quat(rotateZ(rotation_speed * ifps)), 1);
	}

	return 1;
}

In the example above, the node is rotated to the left by pressing the "o" keyboard key.

Notice

It is recommended to set the second argument of the SetWorldRotation() function to 1 for all non-scaled nodes to improve performance and accuracy.
Scaling of nodes should be avoided whenever possible, as it requires addidional calculations and may lead to error accumulation.

To rotate the object by via the WorldTransform variable, you should replace the line with the SetWorldRotation() function in the example above with the following one:

Source code (UnigineScript)

mesh.setWorldTransform(mesh.getWorldTransform() * rotateZ(rotation_speed * ifps));

This way is preferred, especially in case of complex transformations, as it allows to compose transformation matrix and set it only once.

Combining Movements#

Combining different movement controls is not more difficult than adding only one movement control.

The following example adds a mesh to the world and allows you to control it. You can rotate the mesh by using the "o", "[" keyboard keys and move forward by using the "p" key.

Source code (UnigineScript)

// define mesh, player, movement and rotation speed
ObjectMeshStatic mesh;
Player player;
float movement_speed = 5.0f;
float rotation_speed = 30.0f;

/* 
	the world script init() function
 */
int init() {
	// enable visualizer
	engine.visualizer.setEnabled(1);

	// create a camera and add it to the world
	player = new PlayerSpectator();
	player.setPosition(Vec3(4.0f, -3.401f, 1.5f));
	player.setDirection(vec3(0.0f, 1.0f, -0.4f),player.getUp());
	engine.game.setPlayer(player);
	
	// create a mesh by adding a box surface to it
	Mesh mesh_0 = new Mesh();
	mesh_0.addBoxSurface("box_surface", vec3(1.0f));
	// add the mesh to the editor as the ObjectMeshStatic
	mesh = new ObjectMeshStatic(mesh_0);
	// set the mesh position and material
	mesh.setPosition(Vec3(4.0f,0.0f,1.0f));
	mesh.setMaterial("mesh_base", "*");
	
	// check if the key is pressed and update the state of the specified control
	// you can use both 'p', 'o', '[' or ASCII codes (112, 111, 113)
	engine.controls.setStateKey(CONTROLS_STATE_AUX_0, 'p');
	engine.controls.setStateKey(CONTROLS_STATE_AUX_1, 'o');
	engine.controls.setStateKey(CONTROLS_STATE_AUX_2, '[');
	
	return 1;
}

/* 
	the world script update() function
*/
int update() {
	
	// get the frame duration
	float ifps = engine.game.getIFps();

	// get the current world transform matrix of the mesh
	Mat4 transform = mesh.getWorldTransform();

	// get the direction vector of the mesh by using swizzling
	Vec3 direction = transform.m01m11m21;
	
	// initialize rotation, movement, and update flag
	int update_transform = 0;
	quat rotation = quat(0.0f, 0.0f, 0.0f, 0.0f);
	Vec3 delta_movement = Vec3(0.0f);
	
	// render the direction vector for visual clarity
	engine.visualizer.renderDirection(mesh.getWorldPosition(), vec3(direction), vec4(1.0f, 0.0f, 0.0f, 1.0f));
	
	// check if the control key for movement is pressed
	if(engine.controls.getState(CONTROLS_STATE_AUX_0)) {
		// calculate the delta of movement
		delta_movement = direction * movement_speed * ifps;
		update_transform = 1;
	}

	// check if the control key for left rotation is pressed.
	if(engine.controls.getState(CONTROLS_STATE_AUX_1))
	{
		// set the node's rotation along the Z axis
		rotation = quat(rotateZ(rotation_speed * ifps));
		update_transform = 1;
	}
	// check if the control key for right rotation is pressed.
	else if(engine.controls.getState(CONTROLS_STATE_AUX_2))
	{
		// set the node's rotation along the Z axis
		rotation = quat(rotateZ(-rotation_speed * ifps));
		update_transform = 1;
	}
    
	// update transformation if necessary
    if (update_transform)
    {
		// combining transformations: movement + rotation
		transform = transform*rotation;
		transform.col3 += Vec4(delta_movement, 1.0f);
	
		// setting the resulting transformation
		mesh.setWorldTransform(transform);
	}

	return 1;
}

Last update: 2020-07-31

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Basic Object Movements

In This Article:

See Also#

Direction Vector#

Basic Movements#

Moving Forward#

Another Way of Setting Mesh Position

Rotation#

Combining Movements#