# SmoothMover¶

class SmoothMover

This class handles smoothing of sampled motion points over time, e.g. for smoothing the apparent movement of remote avatars, whose positions are sent via occasional telemetry updates.

It can operate in any of three modes: off, in which it does not smooth any motion but provides the last position it was told; smoothing only, in which it smooths motion information but never tries to anticipate where the avatar might be going; or full prediction, in which it smooths motion as well as tries to predict the avatar’s position in lead of the last position update. The assumption is that all SmoothMovers in the world will be operating in the same mode together.

Inheritance diagram

enum PredictionMode
enumerator PM_off = 0
enumerator PM_on = 1
enum SmoothMode
enumerator SM_off = 0
enumerator SM_on = 1
SmoothMover(void)
SmoothMover(SmoothMover const&) = default
void apply_smooth_hpr(NodePath &node) const

Applies the smoothed orientation to the indicated NodePath. This is equivalent to calling node.set_hpr(smooth_mover->get_smooth_hpr()). It exists as an optimization only, to avoid the overhead of passing the return value through Python.

void apply_smooth_pos(NodePath &node) const

Applies the smoothed position to the indicated NodePath. This is equivalent to calling node.set_pos(smooth_mover->get_smooth_pos()). It exists as an optimization only, to avoid the overhead of passing the return value through Python.

void apply_smooth_pos_hpr(NodePath &pos_node, NodePath &hpr_node) const

Applies the smoothed position and orientation to the indicated NodePath. This is equivalent to calling node.set_pos_hpr(smooth_mover->get_smooth_pos(), smooth_mover->get_smooth_hpr()). It exists as an optimization only, to avoid the overhead of passing the return value through Python.

void clear_positions(bool reset_velocity)

Erases all the old position reports. This should be done, for instance, prior to teleporting the avatar to a new position; otherwise, the smoother might try to lerp the avatar there. If reset_velocity is true, the velocity is also reset to 0.

void compute_and_apply_smooth_hpr(NodePath &hpr_node)

A further optimization to reduce Python calls. This computes the smooth position and applies it to the indicated node or nodes in one call. The pos_node and hpr_node might be the same NodePath.

void compute_and_apply_smooth_pos(NodePath &node)

A further optimization to reduce Python calls. This computes the smooth position and applies it to the indicated node in one call.

void compute_and_apply_smooth_pos_hpr(NodePath &pos_node, NodePath &hpr_node)

A further optimization to reduce Python calls. This computes the smooth position and applies it to the indicated node or nodes in one call. The pos_node and hpr_node might be the same NodePath.

bool compute_smooth_position(void)
bool compute_smooth_position(double timestamp)

Computes the smoothed position (and orientation) of the mover at the indicated point in time, based on the previous position reports. After this call has been made, get_smooth_pos() etc. may be called to retrieve the smoothed position.

With no parameter, the function uses ClockObject::get_frame_time() as the default time.

Computes the smoothed position (and orientation) of the mover at the indicated point in time, based on the previous position reports. After this call has been made, get_smooth_pos() etc. may be called to retrieve the smoothed position.

The return value is true if the value has changed (or might have changed) since the last call to compute_smooth_position(), or false if it remains the same.

bool get_accept_clock_skew(void)

Returns the current state of the ‘accept clock skew’ flag. See set_accept_clock_skew().

bool get_default_to_standing_still(void)

Returns the current state of the ‘default to standing still’ flag. See set_default_to_standing_still().

double get_delay(void)

Returns the amount of time, in seconds, to delay the computed position of a SmoothMover. See set_delay().

bool get_directional_velocity(void)

Returns the current state of the ‘directional velocity’ flag. See set_directional_velocity().

double get_expected_broadcast_period(void)

Returns the interval at which we expect the SmoothNodes to broadcast their position, in elapsed seconds. See set_expected_broadcast_period().

LVecBase3 const &get_forward_axis(void) const

Returns the smoothed position as computed by a previous call to compute_smooth_position().

bool get_latest_position(void)

Updates the smooth_pos (and smooth_hpr, etc.) members to reflect the absolute latest position known for this avatar. This may result in a pop to the most recent position.

Returns true if the latest position is known, false otherwise.

double get_max_position_age(void)

Returns the maximum amount of time a position is allowed to remain unchanged before assuming it represents the avatar actually standing still.

double get_most_recent_timestamp(void) const

Returns most recently recorded timestamp

PredictionMode get_prediction_mode(void)

Returns the predictioning mode of all SmoothMovers in the world. See set_prediction_mode().

double get_reset_velocity_age(void)

Returns the amount of time that should elapse after the last position report before the velocity is reset to 0. See set_reset_velocity_age().

LVecBase3 const &get_sample_hpr(void) const

Returns the current orientation of the working sample point. This orientation is updated periodically by set_h(), set_p(), etc., and its current value is copied to the sample point table when mark_position() is called.

LPoint3 const &get_sample_pos(void) const

Returns the current position of the working sample point. This position is updated periodically by set_x(), set_y(), etc., and its current value is copied to the sample point table when mark_position() is called.

PN_stdfloat get_smooth_forward_velocity(void) const

Returns the speed at which the avatar is moving, in feet per second, along its own forward axis (after applying the avatar’s hpr). This will be a positive number if the avatar is moving forward, and a negative number if it is moving backward.

LVecBase3 const &get_smooth_hpr(void) const

Returns the smoothed orientation as computed by a previous call to compute_smooth_position().

PN_stdfloat get_smooth_lateral_velocity(void) const

Returns the speed at which the avatar is moving, in feet per second, along its own lateral axis (after applying the avatar’s hpr). This will be a positive number if the avatar is moving right, and a negative number if it is moving left.

SmoothMode get_smooth_mode(void)

Returns the smoothing mode of all SmoothMovers in the world. See set_smooth_mode().

LPoint3 const &get_smooth_pos(void) const

Returns the smoothed position as computed by a previous call to compute_smooth_position().

PN_stdfloat get_smooth_rotational_velocity(void) const

Returns the speed at which the avatar is rotating in the horizontal plane (i.e. heading), in degrees per second. This may be positive or negative, according to the direction of rotation.

void handle_wrt_reparent(NodePath &old_parent, NodePath &new_parent)

Node is being wrtReparented, update recorded sample positions to reflect new parent

bool has_most_recent_timestamp(void) const

Returns true if we have most recently recorded timestamp

void mark_position(void)

Stores the position, orientation, and timestamp (if relevant) indicated by previous calls to set_pos(), set_hpr(), and set_timestamp() in a new position report.

When compute_smooth_position() is called, it uses these stored position reports to base its computation of the known position.

void output(std::ostream &out) const
void set_accept_clock_skew(bool flag)

Sets the ‘accept clock skew’ flag. When this flag is true, clock skew from the other clients will be tolerated by delaying each smooth mover’s position an additional amount, on top of that specified by set_delay(), based on the measured average latency for timestamp messages received by the client.

In this way, if the other client has significant clock skew with respect to our clock, it will be evident as a large positive or negative average latency for timestamps. By subtracting out this average latency, we compensate for poor clock sync.

void set_default_to_standing_still(bool flag)

Sets the flag that indicates whether to assume that the node stopped moving during periods when we don’t get enough position updates. If true, the object will stand still momentarily. If false, the object will continuously lerp between the position updates that we did get.

void set_delay(double delay)

Sets the amount of time, in seconds, to delay the computed position of a SmoothMover. This is particularly useful when the prediction mode is off, because it can allow the apparent motion of an avatar to appear smooth without relying on prediction, at the cost of introducing additional lag in the avatar’s apparent position.

void set_directional_velocity(bool flag)

Sets the flag that indicates whether the avatar’s direction is considered in computing the velocity. When this is true, velocity is automatically decomposed into a forward and a lateral velocity (and both may be positive or negative); when it is false, all velocity is always returned as forward velocity (and it is always positive).

void set_expected_broadcast_period(double period)

Sets the interval at which we expect the SmoothNodes to broadcast their position, in elapsed seconds. This controls the length of time we assume the object has truly stopped, when we receive a long sequence of no updates.

bool set_h(PN_stdfloat h)

Sets the heading only. See set_hpr().

bool set_hpr(LVecBase3 const &hpr)
bool set_hpr(PN_stdfloat h, PN_stdfloat p, PN_stdfloat r)

Specifies the orientation of the SmoothMover at a particular time in the past. When mark_position() is called, this will be recorded (along with hpr and timestamp) in a position report, which will then be used along with all other position reports to determine the smooth position at any particular instant.

The return value is true if any parameter has changed since the last call to set_hpr(), or false if they are the same.

void set_max_position_age(double age)

Sets the maximum amount of time a position is allowed to remain unchanged before assuming it represents the avatar actually standing still.

bool set_p(PN_stdfloat p)

Sets the pitch only. See set_hpr().

void set_phony_timestamp(double timestamp = 0.0, bool period_adjust = false)

Lies and specifies that the current position report was received now. This is usually used for very old position reports for which we’re not sure of the actual receipt time.

bool set_pos(LVecBase3 const &pos)
bool set_pos(PN_stdfloat x, PN_stdfloat y, PN_stdfloat z)

These methods are used to specify each position update. Call the appropriate set_* function(s), as needed, and then call mark_position(). The return value of each function is true if the parameter value has changed, or false if it remains the same as last time.

Specifies the position of the SmoothMover at a particular time in the past. When mark_position() is called, this will be recorded (along with hpr and timestamp) in a position report, which will then be used along with all other position reports to determine the smooth position at any particular instant.

The return value is true if any parameter has changed since the last call to set_pos(), or false if they are the same.

Specifies the position of the SmoothMover at a particular time in the past. When mark_position() is called, this will be recorded (along with hpr and timestamp) in a position report, which will then be used along with all other position reports to determine the smooth position at any particular instant.

The return value is true if any parameter has changed since the last call to set_pos(), or false if they are the same.

bool set_pos_hpr(LVecBase3 const &pos, LVecBase3 const &hpr)
bool set_pos_hpr(PN_stdfloat x, PN_stdfloat y, PN_stdfloat z, PN_stdfloat h, PN_stdfloat p, PN_stdfloat r)

Specifies the position and orientation of the SmoothMover at a particular time in the past. When mark_position() is called, this will be recorded (along with timestamp) in a position report, which will then be used along with all other position reports to determine the smooth position at any particular instant.

The return value is true if any parameter has changed since the last call to set_pos_hpr(), or false if they are the same.

Specifies the position of the SmoothMover at a particular time in the past. When mark_position() is called, this will be recorded (along with timestamp) in a position report, which will then be used along with all other position reports to determine the smooth position at any particular instant.

The return value is true if any parameter has changed since the last call to set_pos_hpr(), or false if they are the same.

void set_prediction_mode(SmoothMover::PredictionMode mode)

Sets the predictioning mode of all SmoothMovers in the world. If this is PM_off, no prediction will be performed, but smoothing might still be performed.

bool set_r(PN_stdfloat r)

Sets the roll only. See set_hpr().

void set_reset_velocity_age(double age)

Sets the amount of time that should elapse after the last position report before the velocity is reset to 0. This is similar to max_position_age, but it is only used to determine the resetting of the reported velocity. It should always be greater than or equal to max_position_age.

void set_smooth_mode(SmoothMover::SmoothMode mode)

Sets the smoothing mode of all SmoothMovers in the world. If this is SM_off, no smoothing or prediction will be performed, and get_smooth_pos() will simply return the position last set by mark_position().

void set_timestamp(double timestamp)

Specifies the time that the current position report applies. This should be called, along with set_pos() and set_hpr(), before a call to mark_position().

bool set_x(PN_stdfloat x)

Sets the X position only. See set_pos().

bool set_y(PN_stdfloat y)

Sets the Y position only. See set_pos().

bool set_z(PN_stdfloat z)

Sets the Z position only. See set_pos().

void write(std::ostream &out) const