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engine.physics Functions

This set of functions controls the simulation of physics. For more information on principles and implementation of physics in real-time rendering, see the articles Execution Sequence, Physics and Simulation of Physics.

See Also

void engine.physics.addUpdateNode (Node node)

Adds the node which physical state should be updated. If a node is not added with this function, it won't be updated when out of physics simulation distance.

Arguments

  • Node node - Node to be updated.

void engine.physics.addUpdateNodes (int id = [])

Adds multiple nodes which physical state should be updated. If nodes are not added with this function, they won't be updated when out of physics simulation distance.

Arguments

  • int id - Nodes array ID.

float engine.physics.getAngularDamping ()

Returns the current angular damping value.

Return value

Angular damping.

Body engine.physics.getBody (int id)

Returns a body instance by its ID.

Arguments

  • int id - Body ID.

Return value

The body instance.

float engine.physics.getBroadTime ()

Returns the duration of the broad phase, during which potentially colliding objects are found.

Return value

The broad phase duration value, milliseconds.

float engine.physics.getBudget ()

Returns the physics simulation budget. Physics isn't simulated when time is out of the budget.

Return value

The budget value in seconds.

string engine.physics.getData ()

Returns user data associated with the physics. This string is written directly into a *.world file. Namely, into the data child tag of the physics tag, for example:
Source code (XML)
<world version="1.21">
	<physics>
		<data>User data</data>
	</physics>
</world>
		

Return value

User data. Data can contain an XML formatted string.

float engine.physics.getDistance ()

Returns a distance after which the physics will not be simulated.

Return value

Distance in units.

int engine.physics.getFrame ()

Returns the current frame of physics update.

Return value

Frame number.

float engine.physics.getFrozenAngularVelocity ()

Returns the current angular velocity threshold for freezing object simulation. An object stops to be updated if its angular velocity remains lower than this threshold during the number of Frozen frames (together with linear one).

Return value

"Freeze" angular velocity.

float engine.physics.getFrozenLinearVelocity ()

Returns the current linear velocity threshold for freezing object simulation. An object stops to be updated if its linear velocity remains lower than this threshold during the number of Frozen frames (together with angular one).

Return value

"Freeze" linear velocity.

vec3 engine.physics.getGravity ()

Returns the current gravity value.

Return value

Gravity.

float engine.physics.getIFps ()

Returns a physics frame duration.

Return value

Frame duration (1 / FPS).

float engine.physics.getIntegrateTime ()

Returns the duration of the integrate phase, in which physics simulation results are applied to bodies.

Return value

An integrate phase duration value, milliseconds.

Object engine.physics.getIntersection (vec3 p0, vec3 p1, int mask, int exclude[] = [], variable v)

Performs tracing from the p0 point to the p1 point to find an object located on that line. If an object is assigned a body, intersection occurs with its shape. If an object has no body, this function detects intersection with surfaces (polygons) of objects with intersection flag. Intersection is found only for objects with a matching mask. Intersection does not work for disabled objects.

Notice
World space coordinates are used for this function.

Depending on the variable passed as an argument, the result will be presented as following:

Arguments

  • vec3 p0 - Start point of the line.
  • vec3 p1 - End point of the line.
  • int mask - Intersection mask.
  • int exclude[] - Array of the objects to exclude; all these objects will be skipped while checking for intersection.
  • variable v - Variable.

Return value

Reference to the first intersected object, if found; otherwise - 0.

Object engine.physics.getIntersection (vec3 p0, vec3 p1, int mask, variable v)

Performs tracing from the p0 point to the p1 point to find an collision object located on that line. If an object is assigned a body, intersection occurs with its shape. If an object has no body, this function detects intersection with surfaces (polygons) of objects with intersection flag. Intersection is found only for objects with a matching mask.

Notice
World space coordinates are used for this function.

Depending on the variable passed as an argument, the result can be presented as the PhysicsIntersection or PhysicsIntersectionNormal node.

Usage Example

The following example shows how you can get the intersection information by using the PhysicsIntersection class. In this example the line is an invisible traced line from the point of the camera (vec3 p0) to the point of the mouse pointer (vec3 p1). The executing sequence is the following:

  • Define and initialize two points (p0 and p1) by using the Unigine::getPlayerMouseDirection() function from core/scripts/utils.h.
  • Create an instance of the PhysicsIntersection class to get the intersection information.
  • Check, if there is a intersection with an object. The engine.physics.getIntersection() function returns an intersected object when the object intersects with the traced line.
  • In this example, when the object intersects with the traced line, all the surfaces of the intersected object change their material parameters. If the object has a shape, its information will be shown in console. The PhysicsIntersection class instance gets the coordinates of the intersection point, the index of the surface and the Shape class object. You can get all these fields by using getShape(), getPoint() and getSurface() functions
Source code (UnigineScript)
#include <core/scripts/utils.h>
/* ... */
// define two vec3 coordinates
vec3 p0,p1;
// get the mouse direction from camera (p0) to cursor pointer (p1)
Unigine::getPlayerMouseDirection(p0,p1);

// create the instance of the PhysicsIntersection object to save the result
PhysicsIntersection intersection = new PhysicsIntersection();
// create an instance for intersected object and check the intersection
Object object = engine.physics.getIntersection(p0,p1,1,intersection);

// if the intersection has been occurred, change the parameter and the texture of the object's material    
if(object != NULL)
{
  forloop(int i=0; object.getNumSurfaces())
  {
    object.setMaterialParameter("diffuse_color", vec4(1.0f, 0.0f, 0.0f, 1.0f),i);
    object.setMaterialTexture("diffuse","", i);
  }
  
  // if the intersected object has a shape, show the information about the intersection   
  Shape shape = intersection.getShape();
  if (shape != NULL)
  {
    log.message("physics intersection info: point: %s shape: %s surface: %i \n", typeinfo(intersection.getPoint()), typeinfo(shape.getType()), intersection.getSurface());
  }
}
/* ... */
      

Arguments

  • vec3 p0 - Start point of the line.
  • vec3 p1 - End point of the line.
  • int mask - Intersection mask.
  • variable v - Variable defining which type of intersection object will be returned:

Return value

Reference to the first intersected object, if found; otherwise - 0.

Joint engine.physics.getJoint (int num)

Returns a joint by its ID.

Arguments

  • int num - Joint ID.

Return value

The joint.

float engine.physics.getLinearDamping ()

Returns the current linear damping value.

Return value

Linear damping.

float engine.physics.getMaxAngularVelocity ()

Returns the current maximum possible angular velocity.

Return value

Maximum possible angular velocity.

float engine.physics.getMaxLinearVelocity ()

Returns the current maximum possible linear velocity.

Return value

Maximum possible linear velocity.

float engine.physics.getNarrowTime ()

Returns the duration of the narrow phase, during which exact collision tests are performed.

Return value

The narrow phase duration value, milliseconds.

int engine.physics.getNumBodies ()

Returns the number of bodies present within the physics radius.

Return value

The number of bodies.

int engine.physics.getNumContacts ()

Returns the number of contacts within the physics radius; it includes contacts between the bodies (their shapes) and body-mesh contacts.

Return value

The number of contacts.

int engine.physics.getNumFrozenFrames ()

Returns the current number of frames, during which an object should keep certain angular and linear velocities to become frozen.

Return value

Number of frames.

int engine.physics.getNumIslands ()

Returns the number of physical islands within the physics radius that could be calculated separately. The lower this number, the less efficient multi-threading is, if enabled.

Return value

The number of physical islands.

int engine.physics.getNumIterations ()

Returns the current number of iterations used to solve contacts and constraints.

Return value

Current number of iterations.

int engine.physics.getNumJoints ()

Returns the number of joints within the physics radius.

Return value

The number of joints.

float engine.physics.getPenetrationFactor ()

Returns a penalty force factor. 0 means no penalty force in contacts. The maximum value is 1.

Return value

Current penetration factor.

float engine.physics.getPenetrationTolerance ()

Returns a value indicating how deeply one object can penetrate another.

Return value

Current penetration tolerance.

float engine.physics.getResponseTime ()

Returns the duration value of the response phase, in which collision response is calculated and joints are solved.

Return value

A response phase duration value, milliseconds.

float engine.physics.getScale ()

Returns a value used to scale a frame duration.

Return value

Value to scale the frame duration.

Shape engine.physics.getShape (int num)

Returns a shape by its ID.

Arguments

  • int num - Shape ID.

Return value

The shape.

float engine.physics.getSimulationTime ()

Returns the duration of all of the simulation phases added together.

Return value

A simulation phases duration value, milliseconds.

float engine.physics.getTime ()

Returns the current time that can be used when shifting between physics update frames.

Return value

Time in seconds.

float engine.physics.getTotalTime ()

Returns the total time that both rendering and calculating of the frame took (the duration of the main loop in the application execution sequence).

Return value

The total time value, milliseconds.

float engine.physics.getUpdateTime ()

Returns the duration of the update phase, during which the objects are prepared for their collision response to be calculated.

Return value

The update phase duration value, milliseconds.

int engine.physics.isBody (variable v)

Checks a given body for validity. Either a body itself can be passed or the body ID.

Arguments

  • variable v - A body or its ID.

Return value

1 if the variable holds a valid Body instance; otherwise, 0.

int engine.physics.isEnabled ()

Returns a value indicating if physics simulation is enabled.

Return value

1 if physics is enabled; otherwise, 0.

int engine.physics.isFixed ()

Returns a flag indicating if rendering FPS is synchronized to physics one. Such FPS limitation allows to calculate physics each rendered frame (rather then interpolate it when this flag is set to 0). In this mode, there are no twitching of physical objects if they have non-linear velocities. (If the rendering FPS is lower than the physics one, this flag has no effect.)

Return value

1 to cap rendering FPS to physics one; 0 to interpolate physics if rendering FPS is higher.

int engine.physics.isJoint (variable v)

Checks a given joint for validity. Either a joint itself can be passed or the joint ID.

Arguments

  • variable v - A joint or its ID.

Return value

1 if the variable holds a valid Joint instance; otherwise, 0.

int engine.physics.isShape (variable v)

Checks a given shape for validity. Either a shape itself can be passed or the shape ID.

Arguments

  • variable v - A shape or its ID.

Return value

1 if the variable holds a valid Shape instance; otherwise, 0.

int engine.physics.isStable ()

Returns a value that indicates if objects are updated in a definite order or not.

Return value

1 if the objects are updated in a definite order; otherwise 0.

int engine.physics.loadSettings (string file)

Loads physics settings from a given file.

Arguments

  • string file - Path to an XML file with desired settings.

Return value

1 if the settings are loaded successfully; otherwise, 0.

int engine.physics.loadWorld (Xml xml)

Loads physics settings from the given Xml node.

Arguments

  • Xml xml - Xml node.

Return value

1 if settings are loaded successfully; otherwise, 0.

int engine.physics.removeScene (int id)

Removes the previously saved scene.

Arguments

  • int id - ID number of the scene.

Return value

1 if the scene was removed successfully; otherwise, 0.

int engine.physics.restoreScene (int id)

Restores the previously saved scene.

Arguments

  • int id - ID number of the scene.

Return value

1 if the scene was restored successfully; otherwise, 0.

int engine.physics.restoreState (Stream stream)

Restores physics settings from the stream.

Arguments

  • Stream stream - Stream to restore settings from.

Return value

1 if settings are restored successfully; otherwise, 0.

int engine.physics.saveScene ()

Saves the physical properties of all objects in the scene.

Return value

ID number of the saved scene.

int engine.physics.saveSettings (string file, int force = 0)

Saves the current physics settings to a given file.

Arguments

  • string file - Path to a target file.
  • int force - Forced saving of physics settings.

Return value

1 if the settings are saved successfully; otherwise, 0.

int engine.physics.saveState (Stream stream)

Saves physics settings into the stream.

Arguments

  • Stream stream - Stream to save settings into.

Return value

1 if settings are saved successfully; otherwise, 0.

int engine.physics.saveWorld (Xml xml, int force = 0)

Saves the current physics settings into the given Xml node.

Arguments

  • Xml xml - Xml node.
  • int force - Forced saving of physics settings.

Return value

1 if settings are saved successfully; otherwise, 0.

void engine.physics.setAngularDamping (float damping)

Updates the current angular damping value.

Arguments

  • float damping - New angular damping. If a negative value is provided, 0 will be used instead.

void engine.physics.setBudget (float budget)

Sets the physics simulation budget in seconds. Physics isn't simulated when time is out of the budget.

Arguments

  • float budget - The budget value in seconds. The default value is 1/20.

void engine.physics.setData (string data)

Updates user data associated with the physics. This string is written directly into a *.world file. Namely, into the data child tag of the physics tag, for example:
Source code (XML)
<world version="1.21">
	<physics>
		<data>User data</data>
	</physics>
</world>
		

Arguments

  • string data - User data. Data can contain an XML formatted string.

void engine.physics.setDistance (float distance)

Updates a distance after which the physics will not be simulated.

Arguments

  • float distance - Distance in units.

void engine.physics.setEnabled (int mode)

Enables or disables physics simulation.

Arguments

  • int mode - Positive number to enable physics, 0 to disable it.

void engine.physics.setFixed (int fixed)

Sets a flag to synchronize rendering FPS to physics one. Such FPS limitation allows to calculate physics each rendered frame (rather then interpolate it when this flag is set to 0). In this mode, there are no twitching of physical objects if they have non-linear velocities. (If the rendering FPS is lower than the physics one, this flag has no effect.)

Arguments

  • int fixed - 1 to cap rendering FPS to physics one; 0 to interpolate physics if rendering FPS is higher.

void engine.physics.setFrozenAngularVelocity (float velocity)

Updates the angular velocity threshold for freezing object simulation. If the object angular velocity remains lower than this threshold during the number of Frozen frames (together with linear one), it stops to be updated.

Arguments

  • float velocity - New "freeze" angular velocity. If a negative value is provided, 0 will be used instead.

void engine.physics.setFrozenLinearVelocity (float velocity)

Updates the linear velocity threshold for freezing object simulation. If the object linear velocity remains lower than this threshold during the number of Frozen frames (together with angular one), it stops to be updated.

Arguments

  • float velocity - New "freeze" linear velocity. If a negative value is provided, 0 will be used instead.

void engine.physics.setGravity (vec3 gravity)

Updates the current gravity value.

Arguments

  • vec3 gravity - New gravity.

void engine.physics.setIFps (float time)

Updates a frame duration. In fact, this function updates the FPS count used to calculate physics.

Arguments

  • float time - Frame duration (1/FPS).

void engine.physics.setLinearDamping (float damping)

Updates the current linear damping value.

Arguments

  • float damping - New linear damping. If a negative value is provided, 0 will be used instead.

void engine.physics.setMaxAngularVelocity (float velocity)

Updates the maximum possible angular velocity.

Arguments

  • float velocity - New maximum velocity value. If a negative value is provided, 0 will be used instead.

void engine.physics.setMaxLinearVelocity (float velocity)

Updates the maximum possible linear velocity.

Arguments

  • float velocity - New maximum velocity value. If a negative value is provided, 0 will be used instead.

void engine.physics.setNumFrozenFrames (int count)

Updates the number of frames, during which an object should keep certain angular and linear velocities to become frozen.

Arguments

  • int count - Number of frames. If a non-positive value is provided, 1 will be used instead.

void engine.physics.setNumIterations (int iterations)

Updates the number of iterations used to solve contacts and constraints. Note that if this value is too low, the precision of calculations will suffer.

Arguments

  • int iterations - New number of iterations. If a non-positive value is provided, 1 will be used instead.

void engine.physics.setPenetrationFactor (float factor)

Updates the current penalty force factor.

Arguments

  • float factor - New penetration factor. 0 means no penalty force in contacts. The provided value is saturated in the range [0; 1].

void engine.physics.setPenetrationTolerance (float tolerance)

Updates the current penetration tolerance.

Arguments

  • float tolerance - New penetration tolerance. If a negative value is provided, 0 will be used instead, however, this value should be greater than 0 for stable simulation.

void engine.physics.setScale (float factor)

Updates a value that is used to scale a frame duration. The provided value is saturated in the range [0;16].

Arguments

  • float factor - Scaling factor.

void engine.physics.setStable (int stable)

Sets a value that indicates if objects are updated in a definite order or not.

Arguments

  • int stable - 1 to indicate that the objects are updated in a definite order; 0 to indicate that an objects update order may change.

void engine.physics.setTime (float time)

Forces simulation of physics for a given time. It means, until the set time elapses, physics will be calculated each physics tick (frame) that occurs depending on physics frame rate. It allows to control the starting point for physics simulation.

Example code:

Source code (UnigineScript)
int init() {
//to prevent physics from being automatically calculated with each update, set one of the following:
engine.physics.setEnabled(0)
//or
engine.physics.setScale(0)
}

int update() {
//add the time elapsed from the last physics update to the next time count cycle:
engine.physics.setTime(engine.physics.getTime()+ifps));
}
					
In the example, ifps is the time between frames of the renderer.

Arguments

  • float time - Time to continue updating physics in seconds.
Last update: 2017-07-03