Event Handling Callbacks

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.

Usage Example#

The following section contains the complete source code of a simple callback usage example.

world_script.usc

Source code (UnigineScript)

#include <core/unigine.h>
// This file is in UnigineScript language.
// World script, it takes effect only when the world is loaded.

int init() {
	
	Player player = new PlayerSpectator();
	player.setPosition(Vec3(0.0f,3.401f,1.5f));
	player.setDirection(Vec3(0.0f,-1.0f,-0.4f));
	engine.game.setPlayer(player);

	int callback_id = functionid(callback_function);

	call(callback_id);

	return 1;
}

void callback_function() {
	log.message("Callback has been fired\n");
}

// start of the main loop
int update() {

	return 1;
}

int postUpdate() {
	
	return 1;
}

int updatePhysics() {

	return 1;
}
// end of the main loop

int shutdown() {
	
	return 1;
}

Practical Use#

Callbacks are widely used in event handling. A number of Unigine API members have several predefined events which can be handled by using callbacks in certain cases.

Triggers#

Triggers are used to detect changes in nodes position or state. Unigine offers three types of built-in triggers:

NodeTrigger fires callbacks when the trigger node is enabled or the trigger node position has changed.
WorldTrigger fires callbacks when any node (collider or not) gets inside or outside of it.
PhysicalTrigger fires callbacks when physical objects get inside or outside of it.

Here is a simple WorldTrigger usage example:

Source code (UnigineScript)

// implement the enter callback
void enter_callback(Node node) {
		if(node.getType() == NODE_OBJECT_MESH_STATIC) {
		ObjectMeshStatic mesh = node_cast(node);
		mesh.setMaterialState("emission",1,0);
	}
}

WorldTrigger trigger;

int init() {

	// create a world trigger
	trigger = new WorldTrigger(vec3(3.0f));
	// set the enter callback to be fired when a node enters the world trigger
	trigger.setEnterCallback(functionid(enter_callback));
	
	return 1;
}

Widgets#

The widgets base class Widget allows registering callbacks for events defined in the GUI class. The following example shows how to create a WidgetButton and register a callback function for the CLICKED event:

Source code (UnigineScript)

// button clicked callback
void onButtonClicked() {
	/* .. */
}

/* .. */
// getting the system GUI
Gui gui = engine.getGui();

// creating a button widget and setting its caption
widget_button = new WidgetButton(gui,"Press me");

// rearranging button size
widget_button.arrange();

// setting button position
widget_button.setPosition(10,10);

// setting onButtonClicked function to handle CLICKED event by using an intermediate redirecting function
widget_button.setCallback(GUI_CLICKED,functionid(onButtonClicked));

// adding the created button widget to the system GUI
gui.addChild(widget_button,GUI_ALIGN_OVERLAP);

Physics#

You can track certain events of the physics-related Bodies and Joints:

Body.setFrozenCallback() to track an event when a body freezes.
Body.setPositionCallback() to track an event when a body changes its position.
Body.setContactEnterCallback() to track an event when a contact emerges (body starts touching another body or collidable surface).
Body.setContactLeaveCallback() to track an event when a contact ends (body stops touching another body or collidable surface).
Body.setContactsCallback() to get all contacts of the body including new ones (enter) and the ending ones (leave). Leave contacts are removed after the callback execution stage, so this is the only point where you can still get them.
Joint.setBrokenCallback() to track an event when a joint breaks.

The following sample shows the way of registering callbacks for a BodyRigid and change the color of a mesh depending on its state:

Source code (UnigineScript)

// set the node's albedo color to red on freezing event
void frozen_callback(Body body) {
	Object object = body.getObject();
	object.setMaterialParameterFloat4("albedo_color", vec4(1.0f, 0.0f, 0.0f, 1.0f), 0)
}

// set the node's albedo color to blue on position change event
void position_callback(Body body) {
	Object object = body.getObject();
	object.setMaterialParameterFloat4("albedo_color", vec4(0.0f, 0.0f, 1.0f, 1.0f), 0)
}

// set the node's albedo color to yellow on each contact
void contact_enter_callback(Body body, int num) {
	Object object = body.getObject();
	object.setMaterialParameterFloat4("albedo_color", vec4(1.0f, 1.0f, 0.0f, 1.0f), 0)
}

// create a box static mesh
Mesh mesh = new Mesh();
mesh.addBoxSurface("box_0", vec3(1.0f));
ObjectMeshStatic node = new ObjectMeshStatic(mesh);
node.setMaterial("mesh_base", "*");
node.setPosition(Vec3(0, 0, 5.0f));

// add a rigid body
BodyRigid body = new BodyRigid(node);

// register callbacks for events
body.setFrozenCallback(functionid(frozen_callback));
body.setPositionCallback(functionid(position_callback));
body.setContactEnterCallback(functionid(contact_enter_callback));

// add a shape to the body
ShapeBox shape = new ShapeBox(body, vec3(1.0f));

NoticePhysics-based callbacks are executed in the main tread, as they are mainly used for creation, destruction or modification of other objects.

Event Handling Callbacks

In This Article:

Usage Example#

Practical Use#

Triggers#

Widgets#

See Also

Physics#

See Also

See Also#