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@@ -2127,6 +2127,88 @@ CrowdAgents' handle navigation areas differently. The CrowdManager can contains
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See the 39_CrowdNavigation sample application for an example on how to use CrowdAgents and the CrowdManager.
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+
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+\page IK Inverse Kinematics
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+
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+\section Overview
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+
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+IK (Inverse kinematics can be useful in many situations ranging from
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+procedural animation to small adjustments of animation. Simply put, IK is used
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+when you want to position the tips of a hierarchichal structure at a known
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+location and need to calculate all of the rotations of the parent joints to
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+achieve this.
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+
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+Examples include: Moving a hand to pick up an object, or adjusting a foot so
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+it's always touching the ground, regardless of incline, or even precisely
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+ligning up a large tentacle in order to penetrate... Never mind.
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+
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+\image html ik_foot_demo.gif
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+
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+\section Terminology
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+
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+It is good to know some of the terminology used when talking about inverse
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+kinematics, so you can better understand what's being said.
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+
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+\image html ik_terminology.png
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+
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+ - The upper-most node in a solver's tree is known as the \a base \a node or \a root \a node.
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+ - Nodes which need to be moved to a specific target location (example: The hand of a human) are called an \a end \a effector.
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+ - Joints at which multiple children branch off from are called a \a sub-base \a node.
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+ - IK solvers work most efficiently on single "strings" of nodes, which are referred to as \a chains.
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+ - The entire structure (in the case of a human with two hands) is called a \a chain \a tree.
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+
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+\section End Effectors
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+
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+Effectors are used to set the target position and rotation of a node. You can
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+create one by attaching the IKEffector component to a node.
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+
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+\code{.cpp}
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+Node* node = model->GetChild("Hand.R", true);
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+IKEffector* effector = node->CreateComponent<IKEffector>();
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+\endcode
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+
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+The effector has a few parameters that allow you to control how it targets
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+another object. You can set its target position either directly with
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+IKEffector::SetTargetPosition or you can tell it to copy the position and
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+rotation of another node in the scene with IKEffector::SetTargetNode (or, if
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+you only know the name of the node, IKEffector::SetTargetName. If there are
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+multiple nodes in the scene with the same name then the first one found will
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+be used).
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+
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+The target position and rotation are both set in global space.
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+
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+Another important parameter is the \a chain \a length,
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+IKEffector::SetChainLength. A chain length of 1 means a single segment or
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+"bone" is affected. Arms and legs typically use a value of 2 (because you only
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+want to solve for the arm and not the entire body). The default value is 0,
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+which means all nodes right down to the base node are affected.
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+
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+Effectors have a \a weight parameter (use IKEffector::SetWeight) indicating
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+how much influence it has on the tree to be solved. You can make use of this
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+to smoothly transition in and out of IK solutions. This will be required for
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+when your character begins picking up an object and you want to smoothly
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+switch from animation to IK.
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+
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+\code{.cpp}
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+effector->SetWeight(SomeSplineFunction());
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+\endcode
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+
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+\image ik_effector_weight.gif
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+
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+If you've played around with the weight parameter, you may have noticed that
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+it causes a \a linear interpolation of the target position. This can look bad
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+on organic creatures, especially when the solved tree is far apart from the
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+original tree. You might consider enabling \a nlerp, which causes the weight
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+to rotate around the next sub-base joint. This feature can be enabled with
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+IKEffector::EnableWeightedNlerp.
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+
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+
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+
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+If required, you can also set the target rotation with
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+IKEffector::SetTargetRotation. Note that this is disabled by default (more on
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+this later in the solver section).
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+
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+
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\page UI User interface
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Urho3D implements a simple, hierarchical user interface system based on rectangular elements. The elements provided are:
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