Basic Object Movements

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 and movement speed
ObjectMeshStatic mesh;
float movement_speed = 5.0f;

// add a mesh as a node to the editor
Node add_editor(Node node) {
	engine.editor.addNode(node);
	return node_remove(node);
}

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

	// create a camera and add it to the world
	Player 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 = add_editor(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));
	
	// 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 using the setWorldTransform() function. 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 via the setWorldTransform() function or via the setWorldRotation() function. The following example uses the second one:

Source code (UnigineScript)

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

// add a mesh as a node to the editor
Node add_editor(Node node) {
	engine.editor.addNode(node);
	return node_remove(node);
}

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

	// create a camera and add it to the world
	Player 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 = add_editor(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
		mesh.setWorldRotation(mesh.getWorldRotation() * quat(rotateZ(rotation_speed * ifps)));
	}

	return 1;
}

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

To rotate the object by using the setWorldTransform() function, you should replace the setWorldRotation() function with the following line:

Source code (UnigineScript)

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

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 the ObjectMeshStatic mesh, the movement and rotation speed
ObjectMeshStatic mesh;
float movement_speed = 5.0f;
float rotation_speed_left = 30.0f;
float rotation_speed_right = -30.0f;

// add a mesh as a node to the editor
Node add_editor(Node node) {
	engine.editor.addNode(node);
	return node_remove(node);
}

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

	// create a camera and add it to the world
	Player 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 = add_editor(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;
	
	// 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
		Vec3 delta_movement = direction * movement_speed * ifps;

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

	// check if the control key for left rotation is pressed.
	if(engine.controls.getState(CONTROLS_STATE_AUX_1)) {
		// set the node rotation along the Z axis
		mesh.setWorldRotation(mesh.getWorldRotation() * quat(rotateZ(rotation_speed_left * ifps)));
	}
	
	// check if the control key for right rotation is pressed.
	if(engine.controls.getState(CONTROLS_STATE_AUX_2)) {
		// set the node rotation along the Z axis
		mesh.setWorldRotation(mesh.getWorldRotation() * quat(rotateZ(rotation_speed_right * ifps)));
	}

	return 1;
}

Last update: 2017-12-21

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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