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improve Body.applyForce docs

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liabru 2022-12-28 23:48:56 +00:00
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commit 3a8264c671
1 changed files with 14 additions and 7 deletions
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src/body/Body.js
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@ -801,15 +801,22 @@ var Axes = require('../geometry/Axes');
};
/**
* Applies a force to a body from a given world-space position for a _single update_, including resulting torque.
* The position must be specified. Using `body.position` results in zero torque.
* Applies the `force` to the `body` from the force origin `position` in world-space, over a single timestep, including applying any resulting angular torque.
*
* Forces create an acceleration that acts over time, so may need to be applied over multiple updates for the body to gain a visible momentum.
* Forces are useful for effects like gravity, wind or rocket thrust, but can be difficult in practice when precise control is needed. In these cases see `Body.setVelocity` and `Body.setPosition` as an alternative.
*
* See also `Body.setVelocity` and related methods which do not require any time for acceleration to reach the given velocity.
* The force from this function is only applied once for the duration of a single timestep, in other words the duration depends directly on the current engine update `delta` and the rate of calls to this function.
*
* Therefore to account for time, you should apply the force constantly over as many engine updates as equivalent to the intended duration.
*
* If all or part of the force duration is some fraction of a timestep, first multiply the force by `duration / timestep`.
*
* The force origin `position` in world-space must also be specified. Passing `body.position` will result in zero angular effect as the force origin would be at the centre of mass.
*
* The `body` will take time to accelerate under a force, the resulting effect depends on duration of the force, the body mass and other forces on the body including friction combined.
* @method applyForce
* @param {body} body
* @param {vector} position
* @param {vector} position The force origin in world-space. Pass `body.position` to avoid angular torque.
* @param {vector} force
*/
Body.applyForce = function(body, position, force) {
@ -988,7 +995,7 @@ var Axes = require('../geometry/Axes');
/**
* A `Vector` that accumulates the total force applied to the body for a single update.
* Force is zeroed after every `Body.update`, so constant forces should be applied for every update they are needed. See also `Body.applyForce`.
* Force is zeroed after every `Engine.update`, so constant forces should be applied for every update they are needed. See also `Body.applyForce`.
*
* @property force
* @type vector
@ -997,7 +1004,7 @@ var Axes = require('../geometry/Axes');
/**
* A `Number` that accumulates the total torque (turning force) applied to the body for a single update. See also `Body.applyForce`.
* Torque is zeroed after every `Body.update`, so constant torques should be applied for every update they are needed.
* Torque is zeroed after every `Engine.update`, so constant torques should be applied for every update they are needed.
*
* Torques are converted to acceleration on every update, which depends on body inertia and the engine update delta.
*