/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Copyright (C) 2017 Klaralvdalens Datakonsult AB (KDAB).
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \module Qt3DAnimation
    \title Qt 3D Animation C++ Classes

    \brief The Qt 3D Animation module provides a set of prebuilt elements to help
    you get started with Qt 3D.

    This module is still in tech preview. This means it is unstable, likely to
    change and provided as a convenience only.

    \ingroup modules
    \ingroup qt3d-modules
    \qtvariable 3danimation

    \code
       #include <Qt3DAnimation>
    \endcode

    To link against the corresponding C++ library, add the following to your qmake project file:

    \badcode
       QT += 3danimation
    \endcode

    Classes, types, and functions are declared under the \l [Qt3DAnimation]{Qt3DAnimation} namespace.

    \section1 Overview

    The Qt 3D Animation module adds support for specifying and using animations
    that can be applied to the properties of objects in your simulation.
    Initially this module supports key frame based animations. That is,
    properties have values 'keyed' at certain times and when played back the
    property values are calculated by interpolating between the known values
    within the key frames. All of the animation evaluation within the Qt 3D
    Animation module takes place on the Qt 3D threadpool. This allows the
    animations to run smoothly and to scale up to high throughput.

    \section2 Animation Data

    Key frame animation data can either be created programmatically via the Qt
    3D Animation APIs such as Qt3DAnimation::QKeyFrameData or it can come from
    digital content creation (DCC) tools such as Blender, Maya or 3D Studio
    Max. Qt 3D provides an example export script for animation data for
    Blender. The format consumed by Qt 3D Animation at present is a simple JSON
    based format. This allows both developers and artists to easily work with
    animation data. More formats optimised for runtime consumption will be
    added later.

    The key frame animation data can be loaded from file using the
    Qt3DAnimation::QAnimationClipLoader class. To specify animation data
    programmatically use the Qt3DAnimation::QAnimationClip class.

    By default, the key frame data is specified using cubic bezier curves. This
    allows smooth animations to be created from a small number of key frame
    data points. Other interpolation types will be added later.

    \section2 Playing Animations

    In addition to the animation data containing the key frames, Qt 3D
    Animation also provides APIs for playing the animations and mapping the
    resulting property values onto properties of objects in your simulation.
    There are currently two ways of playing the animations:

    \list
    \li Qt3DAnimation::QClipAnimator
    \li Qt3DAnimation::QBlendedClipAnimator
    \endlist

    Both of these are implemented as subclasses of Qt3DCore::QComponent meaning
    that objects of these types can be aggregated by Qt3DCore::QEntity objects
    to add animation capabilities to your simulated entities.

    \section2 Simple Animation Playback

    The Qt3DAnimation::QClipAnimator class allows the playback of a single
    Qt3DAnimation::QAbstractAnimationClip at a time. To add an animation to an
    entity, simply add an instance of the Qt3DAnimation::QClipAnimator class to
    your entity's \c components property.

    The Qt 3D Animation module takes a slightly different approach to
    QPropertyAnimation and AbstractAnimation. With those animation frameworks,
    the animation specifies both the animation values \e {and} the target
    objects and properties. The animation components in Qt 3D separate these
    two orthogonal concepts. For example, the Qt3DAnimation::QClipAnimator
    component has a \c clip property for specifying the animation data
    (Qt3DAnimation::QAnimationClip or Qt3DAnimation::QAnimationClipLoader).

    This allows calculation of the animated values, but more information is
    needed in order to map these values onto properties of objects. This is
    accomplished with the a Qt3DAnimation::QChannelMapper which contains a list
    of Qt3DAnimation::QChannelMapping objects. A Qt3DAnimation::QChannelMapping
    is used to map a specific channel from an animation clip onto a named
    property of a target object. By separating the animation data and property
    mappings like this, the same animation can be applied to many objects
    without needing to have multiple copies of the animation data or objects.
    It also allows animation data to easily be retargeted to other objects.

    \section2 Blended Animation Playback

    The Qt3DAnimation::QBlendedClipAnimator component allows to go beyond what
    is possible with Qt3DAnimation::QClipAnimator by blending several animation
    clips together before applying the property changes to the target
    properties. The animator component still takes a channel mapper just like
    the standard Qt3DAnimation::QClipAnimator component. However, instead of
    specifying a single animation clip, it is necessary to set the \c blendTree
    property to point to the root node of a \e {blend tree}.

    A blend tree is a data structure representing how animation clips get
    aggregated or blended together as the function of properties on the blend
    tree nodes. The currently supported set of blend tree nodes are:

    \list
    \li Qt3DAnimation::QClipBlendValue
    \li Qt3DAnimation::QLerpClipBlend
    \li Qt3DAnimation::QAdditiveClipBlend
    \endlist

    The source animation clip inputs are specified as leaf nodes in the blend
    tree using instances of the Qt3DAnimation::QClipBlendValue class. These
    animation clips can be combined in a large number of ways. For now the Qt3D
    Animation module provides linear interpolation (LERP) and additive blend
    operations. More blend node types will be added over time. These are
    expected to include at least a generalised LERP node and a barycentric LERP
    node.

    As an example consider the following blend tree:

    \badcode
        Clip0----
                |
                Lerp Node----
                |           |
        Clip1----           Additive Node
                            |
                    Clip2----
    \endcode

    Let's assume that \c Clip0 represents a walk animation cycle with a
    duration of 3 seconds and that \c Clip1 is a run animation cycle with a
    duration of 2 seconds. These are both inputs (and dependencies) of the \c
    Lerp blend node. The result of evaluating the \c Lerp node depends upon the
    \c blendFactor property of the \c Lerp node. This could be bound to the
    speed of a humanoid character entity for example. As the speed of the
    character increases the animation gradually cross-fades from the walk
    animation in \c Clip0 to the run animation in \c Clip1.

    Furthermore, let's assume that \c Clip2 represents some variation animation
    that can be added on (waving arms or shaking head for e.g.). The amount of
    this additive clip that is added can be controlled by the \c additiveFactor
    property on the \c Additive blend node.

    When evaluating a blend tree, normalized time (or phase) is used so that
    clips of different durations can be blended together without problems. For
    example, even though the walk and run animation clips are of different
    lengths, as long as they are created by the animator such that the
    foot-falls line up at the same phase these can be nicely interpolated.

    The implication of this is that the duration of the blended clip is
    actually a function of the blend factors of the nodes in the tree.
    Considering only the \c Lerp node in the above example, when the blend
    factor of the \c Lerp node is 0, only the walk animation in Clip0 is used
    resulting in a duration of 3 seconds. With a blend factor of 1 the
    resulting duration will be 2 seconds. For intermediate blend factors, the
    duration will be linearly interpolated between 3 and 2 seconds.

    By definining your own blend trees, you have complete control over how to
    combine your collection of input animation clips. The blend tree can be
    configured by the properties on the blend nodes. Note also that the
    properties on the blend nodes themselves are just standard properties, so
    these could in turn be driven by other animations if desired.

    \section1 Reference
    \list
    \li \l {Qt 3D Animation C++ Classes}
    \li \l {Qt 3D Examples}
    \endlist
 */

/*!
    \namespace Qt3DAnimation
    \inmodule Qt3DAnimation
    \ingroup qt3d-namespaces

    \brief Contains classes from the Qt3DAnimation module.
*/

/*!
   \qmlmodule Qt3D.Animation 2.9
   \title Qt 3D Qt3DAnimation QML Types
   \ingroup qmlmodules
   \ingroup qt3d-qmlmodules

   \brief Provides Qt 3D QML types for the animation module.

   To import and use the module's QML types, use the following statement:

   \badcode
   import Qt3D.Animation 2.9
   \endcode
*/
