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functions:llapplyrotationalimpulse [2015-01-09 18:38 SLT] sei Add complete example, add llTargetOmega to See Also |
functions:llapplyrotationalimpulse [2016-11-03 18:18 SLT] (current) sei speed -> velocity |
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| </code> | </code> | ||
| - | Apply an instant change to the angular momentum of a physical object. It has no effect on non-physical objects. | + | Apply an instant change to the angular momentum of a physical object. It has no effect on non-physical objects or on attachments. |
| ===== Parameters ===== | ===== Parameters ===== | ||
| === impulse === | === impulse === | ||
| - | A [[types/vector]] specifying the impulse to apply, which will add to the object's current [[http://en.wikipedia.org/wiki/Angular_momentum|angular momentum]]. The vector indicates the impulse's axis and magnitude. The units of the angular impulse vector seem to be [[lsl/lindograms]]·m²/s. Like in the real world, the effect on the angular velocity depends not only on the mass of the object, but also on its shape, as it's the product of [[http://en.wikipedia.org/wiki/Moment_of_inertia|moment of inertia]] (which itself depends on the [[http://en.wikipedia.org/wiki/List_of_moments_of_inertia|shape of the object]]) and angular velocity. | + | A $lty[vector] specifying the impulse to apply, which will add to the object's current [[http://en.wikipedia.org/wiki/Angular_momentum|angular momentum]]. The vector's direction indicates the impulse's axis and its length indicates the magnitude. The units of the angular impulse vector seem to be $lart[lindogram|lindograms]·m²/s. Like in the real world, the effect on the angular velocity depends not only on the mass of the object, but also on its shape, as it's the product of [[http://en.wikipedia.org/wiki/Moment_of_inertia|moment of inertia]] (which itself depends on the [[http://en.wikipedia.org/wiki/List_of_moments_of_inertia|shape of the object]]) and angular velocity. |
| === local === | === local === | ||
| - | [[types/Boolean]] value indicating whether the **impulse** axis' coordinates are local to the root prim (if [[constants/TRUE]]) or in sim coordinates (if [[constants/FALSE]]). | + | $lty[Boolean] value indicating whether the $prm[impulse] axis' coordinates are local to the root prim (if $lct[TRUE]) or in sim coordinates (if $lct[FALSE]). |
| - | When **TRUE**, the **impulse** axis' coordinates are local to the root prim. For example, if **impulse** is `<1, 0, 0> and the X axis of the root prim is looking northwest, then the impulse will have its axis oriented in the northwest direction, aligned with the root prim's X axis. | + | When $ct[TRUE], the $prm[impulse] axis' coordinates are local to the root prim. For example, if $prm[impulse] is `<1, 0, 0> and the X axis of the root prim is looking northwest, then the impulse will have its axis oriented in the northwest direction, aligned with the root prim's X axis. |
| - | When **FALSE**, the vector specifies sim coordinates, where positive X is east, positive Y is north, positive Z is up, and vice versa for negative; for example, if **impulse** is `<-1, 0, 0>, the rotational impulse will have its axis pointing west, no matter how the root prim is oriented. | + | When $ct[FALSE], the vector specifies sim coordinates, where positive X is east, positive Y is north, positive Z is up, and vice versa for negative; for example, if $prm[impulse] is `<-1, 0, 0>, the rotational impulse will have its axis pointing west, no matter how the root prim is oriented. |
| + | |||
| + | ===== Notes ===== | ||
| + | |||
| + | * The maximum angular velocity of an object seems to be about 127 rad/s (about 1212 rpm). Note, however, that $lfn[llGetOmega] will not return a value with a magnitude greater than 62.8 rad/s (about 599.7 rpm). | ||
| ===== Short examples ===== | ===== Short examples ===== | ||
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| llApplyRotationalImpulse(<0, 0, 1>, TRUE); | llApplyRotationalImpulse(<0, 0, 1>, TRUE); | ||
| // 0.6 rad/s is derived from the moment of inertia of a cube spinning over its | // 0.6 rad/s is derived from the moment of inertia of a cube spinning over its | ||
| - | // axis (m*l*l/6, where l is the length of the side) and the impulse applied. | + | // axis (m*l^2/6, where l is the length of the side) and the impulse applied. |
| // The mass of such a cube is 10 lindograms. Measurement with llGetOmega | // The mass of such a cube is 10 lindograms. Measurement with llGetOmega | ||
| // indicates that it works this way. | // indicates that it works this way. | ||
| Line 35: | Line 39: | ||
| ===== Complete examples ===== | ===== Complete examples ===== | ||
| - | This example verifies the physical accuracy of **llApplyRotationalImpulse** on an undeformed box of any dimensions. Moment of inertia varies with shape, so most deformations affect the results. | + | This example verifies the physical accuracy of $fn[llApplyRotationalImpulse] on an undeformed box of any dimensions. Moment of inertia varies with shape, so most deformations affect the results. |
| - | <code lsl2 llApplyRotationalImpulse-test> | + | <code lsl2 llApplyRotationalImpulse-test.lsl> |
| float IMPULSE = 1.31; // change this value to any value to test | float IMPULSE = 1.31; // change this value to any value to test | ||
| default | default | ||
| { | { | ||
| - | state_entry() | + | touch_start(integer n) |
| { | { | ||
| - | llSetStatus(STATUS_PHYSICS, FALSE); | + | // Disable gravity, enable physics, wait for the setting to take effect |
| - | vector size = llGetScale(); | + | |
| - | llSleep(0.2); | + | |
| llSetPhysicsMaterial(GRAVITY_MULTIPLIER, 0, 0, 0, 0); | llSetPhysicsMaterial(GRAVITY_MULTIPLIER, 0, 0, 0, 0); | ||
| - | } | ||
| - | |||
| - | touch_start(integer n) | ||
| - | { | ||
| - | // Enable physics, wait for the engine to detect it | ||
| llSetStatus(STATUS_PHYSICS, TRUE); | llSetStatus(STATUS_PHYSICS, TRUE); | ||
| llSleep(0.5); | llSleep(0.5); | ||
| Line 64: | Line 61: | ||
| // times. Sometimes we're lucky and get the actual value. | // times. Sometimes we're lucky and get the actual value. | ||
| vector omega = llGetOmega(); | vector omega = llGetOmega(); | ||
| - | vector size = llGetScale(); | ||
| // Disable physics again, return to zero rotation. | // Disable physics again, return to zero rotation. | ||
| Line 70: | Line 66: | ||
| llSetRot(<0, 0, 0, 1>); | llSetRot(<0, 0, 0, 1>); | ||
| + | // Calculate and report results. | ||
| + | vector size = llGetScale(); | ||
| + | // Predicted omega is impulse divided by moment of inertia. | ||
| + | // Moment of inertia of a box rotating on its z axis is m*(size.x²+size.y²)/12. | ||
| float predicted = IMPULSE/(llGetMass()*(size.x*size.x+size.y*size.y)/12); | float predicted = IMPULSE/(llGetMass()*(size.x*size.x+size.y*size.y)/12); | ||
| llSay(0, "Theoretical omega: " + (string)predicted | llSay(0, "Theoretical omega: " + (string)predicted | ||
| Line 81: | Line 81: | ||
| ===== See also ===== | ===== See also ===== | ||
| - | * [[llApplyImpulse]] is similar but for [[http://en.wikipedia.org/wiki/Momentum|linear momentum]] instead of angular. | + | * $lfn[llApplyImpulse] is similar but for [[http://en.wikipedia.org/wiki/Momentum|linear momentum]] instead of angular. |
| - | * [[llSetAngularVelocity]] applies the rotational impulse necessary to set the given angular velocity for an object. | + | * $lfn[llSetAngularVelocity] applies the rotational impulse necessary to set the given angular velocity for an object. |
| - | * [[llGetOmega]] obtains the current angular velocity of the object. | + | * $lfn[llGetOmega] obtains the current angular velocity of the object. |
| - | * [[llTargetOmega]] tries to keep a constant angular speed. | + | * $lfn[llTargetOmega] tries to keep a constant angular velocity. |
| - | * [[llSetTorque]] applies an angular force (a torque) to an object continuously | + | * $lfn[llSetTorque] applies an angular force (a torque) to an object continuously |
| - | * [[llSetForce]] is the linear equivalent to **llSetTorque**. | + | * $lfn[llSetForce] is the linear equivalent to $fn[llSetTorque]. |
| - | * [[llSetForceAndTorque]] sets both force and torque at the same time. | + | * $lfn[llSetForceAndTorque] sets both force and torque at the same time. |
| - | * [[llSetVelocity]] and [[llGetVel]] are the linear equivalents of **llSetAngularVelocity/llGetOmega**. | + | * $lfn[llSetVelocity] and $lfn[llGetVel] are the linear equivalents of $fn[llSetAngularVelocity]/$fn[llGetOmega]. |
| - | * [[llGetMass]] returns the mass in Lindograms of an object. | + | * $lfn[llGetMass] returns the mass in $lart[lindogram|Lindograms] of an object. |
| - | * [[llGetMassMKS]] returns the mass in kilograms of an object. Most LSL functions use Lindograms, so this function is of limited use in physics calculations. | + | * $lfn[llGetMassMKS] returns the mass in kilograms of an object. Most LSL functions use $art[Lindograms], so this function is of limited use in physics calculations. |
| + | * $lfn[llVecNorm] to obtain a unit vector from a given one. | ||