alias_api.AlAction

class alias_api.AlAction

Bases: AlObject

Basic interface to Alias actions

AlAction is the base class for an Alias action. An action is an entity that will map time to a value. In Alias, there are two types of actions: parameter curve actions, represented by the derived class AlParamAction, and motion path actions, represented by the derived class AlMotionAction.

You can create new AlActions by creating an AlParamAction or an AlMotionAction. Existing actions can be accessed either through the global list of actions (first_action(), next_action()) or through the list of actions which a channel uses to animate a field of an item (AlChannel.applied_action()). Note that if you delete an action, it may cause other classes to be deleted (for example, AlKeyframe, and AlChannel if the action was the base action of a channel).

channel_reference(self: alias_api.AlAction, arg0: SupportsInt) → alias_api.AlChannel

This method returns the ‘n’th AlChannel that references this AlAction. If ‘n’ is less than 1, or greater than the number of channels that reference this action (as returned by AlAction::numChannelReferences()), then NULL is returned. The list of channels is not in any particular order.

Parameters: n (int) – the index between 1 and numChannelReferences() of the channel reference to return.
Returns: The ‘n’th AlChannel that references this AlAction.
Return type: AlChannel

comment(self: alias_api.AlAction) → str: This method returns the comment on the action.

copy(self: alias_api.AlAction) → alias_api.AlAction: This method makes a copy of this action and returns the copy. If the copy fails, NULL is returned. Note that this method copies the action NOT the wrapper object.

eval(self: alias_api.AlAction, time: typing.SupportsFloat, compo: alias_api.AlTripleComponent = <AlTripleComponent.X_Component: 1>) → float

This method evaluates this action at the given time, and returns the value of the action at that time. If the action is an AlMotionAction, then you must specify which component of the resulting (x,y,z) value to retrieve using the optional second argument.

If the action is not valid, 0.0 is returned.

Evaluation of an AlParamAction is as follows:

An animation parameter curve is a “Poon-Ross” spline (developed by Angus Poon and Dave Ross). This spline is basically a Hermite-linear spline. That is, it is a Hermite in y (the vertical axis) and a linear in x (the horizontal axis). If we call this spline C(t) = (x(t), y(t)), then we see that it is fairly straightforward to compute for the case when x = T since x(t) = t. So we would get C(t) for x = T is (T, y(T)).

To compute a point on a curve segment C(t) (which is bounded by the cvs (t1, y1), (t2, y2) and has tangents m1 and m2 at the start & end of the segment) at t = T, we first make the mapping

T’ = (T - t1) / (t2 - t1)

so that t is in the range [0, 1]. We then get the y value off of the curve segment using the standard computation

C(T) = [T’^3 T’^2 T’ 1] * H *%@ | y1 |

where H is the hermite basis matrix.

Parameters

time (float) – the time at which to evaluate the action
compo (AlTripleComponent) – which component to get, for motion actions.

Returns

The value of the action at the given time.

Return type

float

extrap_type_post(self: alias_api.AlAction) → alias_api.AlActionExtrapType

This method returns the out-of-range, or extrapolation to infinite type of the action after its defined range. If the type can not be retrieved, kEXTRAP_INVALID is returned.

Return type: AlActionExtrapType

extrap_type_pre(self: alias_api.AlAction) → alias_api.AlActionExtrapType

This method gets the out-of-range, or extrapolation to infinite type of the action before its defined range. If the type could not be retrieved, Invalid is returned.

Return type: AlActionExtrapType

property name: Get or set the AlAction name.

num_channel_references(self: alias_api.AlAction) → int: This method returns the number of channels that use this action. If 0 is returned, this action is considered non-referenced. Note that if one channel uses this action 2 times, this is counted as 2 references. Also note that if the action is not valid -1 will be returned.

set_comment(self: alias_api.AlAction, new_comment: str) → int

This method makes a copy of ‘newComment’ and replaces the existing comment on the action with this new comment.

Parameters: new_comment (str) – the new comment to assign to the action
Returns: The status code result of the operation: Success - action’s comment was changed to newComment InvalidArgument - newComment was NULL InvalidObject - this action is not valid
Return type: AlStatusCode

set_extrap_type_post(self: alias_api.AlAction, extrap_type: alias_api.AlActionExtrapType) → int

This method sets the out-of-range, or extrapolation to infinite type of the action after its defined range to the given extrapolation type.

Parameters: extrap_type (AlActionExtrapType) – extrapolation type to set for action after defined range
Returns: The status code result of the operation: Success - the extrapolation type was successfully determined InvalidObject - the action was not valid InvalidArgument - the given extrapolation type was not valid.
Return type: AlStatusCode

set_extrap_type_pre(self: alias_api.AlAction, extrap_type: alias_api.AlActionExtrapType) → int

This method sets the out-of-range, or extrapolation to infinite type of the action before its defined range to the given extrapolation type.

Parameters: extrap_type (AlActionExtrapType) – extrapolation type to set for action before defined range
Returns: The status code result of the operation: Success - the extrapolation type was successfully determined InvalidObject - the action was not valid InvalidArgument - the given extrapolation type was not valid.
Return type: AlStatusCode

type(self: alias_api.AlAction) → alias_api.AlObjectType: Returns the class identifier ‘ActionType’.