| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation (qt-info@nokia.com)
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at qt-info@nokia.com.
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \example animation/stickman
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| 30 | \title Stickman Example
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| 31 |
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| 32 | The Stickman example shows how to animate transitions in a state machine to implement key frame
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| 33 | animations.
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| 34 |
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| 35 | \image stickman-example.png
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| 36 |
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| 37 | In this example, we will write a small application which animates the joints in a skeleton and
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| 38 | projects a stickman figure on top. The stickman can be either "alive" or "dead", and when in the
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| 39 | "alive" state, he can be performing different actions defined by key frame animations.
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| 40 |
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| 41 | Animations are implemented as composite states. Each child state of the animation state
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| 42 | represents a frame in the animation by setting the position of each joint in the stickman's
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| 43 | skeleton to the positions defined for the particular frame. The frames are then bound together
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| 44 | with animated transitions that trigger on the source state's propertiesAssigned() signal. Thus,
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| 45 | the machine will enter the state representing the next frame in the animation immediately after
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| 46 | it has finished animating into the previous frame.
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| 47 |
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| 48 | \image stickman-example1.png
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| 49 |
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| 50 | The states for an animation is constructed by reading a custom animation file format and
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| 51 | creating states that assign values to the the "position" properties of each of the nodes in the
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| 52 | skeleton graph.
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| 53 |
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| 54 | \snippet examples/animation/stickman/lifecycle.cpp 1
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| 55 |
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| 56 | The states are then bound together with signal transitions that listen to the
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| 57 | propertiesAssigned() signal.
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| 58 |
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| 59 | \snippet examples/animation/stickman/lifecycle.cpp 2
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| 60 |
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| 61 | The last frame state is given a transition to the first one, so that the animation will loop
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| 62 | until it is interrupted when a transition out from the animation state is taken. To get smooth
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| 63 | animations between the different key frames, we set a default animation on the state machine.
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| 64 | This is a parallel animation group which contains animations for all the "position" properties
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| 65 | and will be selected by default when taking any transition that leads into a state that assigns
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| 66 | values to these properties.
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| 67 |
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| 68 | \snippet examples/animation/stickman/lifecycle.cpp 3
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| 69 |
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| 70 | Several such animation states are constructed, and are placed together as children of a top
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| 71 | level "alive" state which represents the stickman life cycle. Transitions go from the parent
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| 72 | state to the child state to ensure that each of the child states inherit them.
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| 73 |
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| 74 | \image stickman-example2.png
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| 75 |
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| 76 | This saves us the effort of connect every state to every state with identical transitions. The
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| 77 | state machine makes sure that transitions between the key frame animations are also smooth by
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| 78 | applying the default animation when interrupting one and starting another.
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| 79 |
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| 80 | Finally, there is a transition out from the "alive" state and into the "dead" state. This is
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| 81 | a custom transition type called LightningSrikesTransition which samples every second and
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| 82 | triggers at random (one out of fifty times on average.)
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| 83 |
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| 84 | \snippet examples/animation/stickman/lifecycle.cpp 4
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| 85 |
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| 86 | When it triggers, the machine will first enter a "lightningBlink" state which uses a timer to
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| 87 | pause for a brief period of time while the background color of the scene is white. This gives us
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| 88 | a flash effect when the lightning strikes.
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| 89 |
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| 90 | \snippet examples/animation/stickman/lifecycle.cpp 5
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| 91 |
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| 92 | We start and stop a QTimer object when entering and exiting the state. Then we transition into
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| 93 | the "dead" state when the timer times out.
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| 94 |
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| 95 | \snippet examples/animation/stickman/lifecycle.cpp 0
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| 96 |
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| 97 | When the machine is in the "dead" state, it will be unresponsive. This is because the "dead"
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| 98 | state has no transitions leading out.
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| 99 |
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| 100 | \image stickman-example3.png
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| 101 |
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| 102 | */
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