FBX SDK Programmer's Guide > Animation >

# Evaluating the Animation in a Scene

To render an animated scene (FbxScene), you must evaluate the animated properties of objects (FbxObject) in a scene at different points in time. For example, to display a moving race car that is represented by a mesh, you must animate the local translation property of the node whose node attribute is the mesh. See FbxNode::LclTranslation.

Perform the following steps to evaluate the animation in a scene:

1. Get an evaluator object from the scene object that contains the node.

       // Let us assume that myScene is already created
       FbxAnimEvaluator* mySceneEvaluator = MyScene->GetEvaluator();

2. Create a time object.

       FbxTime myTime;       // The time for each key in the animation curve(s)
       myTime.SetSecondDouble(0.0);   // Starting time

3. Create a node object.

       // Create a node object
       FbxNode* myMeshNode = FbxNode::Create (myScene, "");
       // ... Code to connect myMeshNode to a mesh object

4. Get the global transformation matrix or local transformation matrix of the node at a specific time.
   - To get the global transformation matrix:

         // Get a reference to node’s global transform.
         FbxMatrix& GlobalMatrix = mySceneEvaluator->GetNodeGlobalTransform(myMeshNode, myTime);

   - To get the local transformation matrix:

         // Get a reference to node’s local transform.
         FbxMatrix& GlobalMatrix = mySceneEvaluator->GetNodeLocalTransform(myMeshNode, myTime);

5. Evaluate the camera’s position expressed as a vector at a specific time.
   NoteA transformation matrix is not needed to evaluate a camera's position.

       // Given a scene, we can create a camera
       FbxCamera* myCamera = FbxCamera::Create (myScene, "");

       // Store the value of the property in an animation curve node
       FbxAnimCurveNode&  myCameraPositionVector;

       // Get and store the value of the camera's local translation
       myCameraPositionVector = mySceneEvaluator->GetPropertyValue (myCamera->Position, myTime);

See Animation/main.cxx for an example that illustrates the use of animation stacks, animation layers, animation curve nodes, and animation curves.

## Using the Animation Curve Node to Store the Value of a FBX Property

In the code snippet above, the FbxAnimCurveNode object is not used as a connection point between an animation curve and a FBX property. Instead, FbxAnimCurveNode is used as a convenient place to store the vector of the property returned by the evaluator. The animatable properties of FBX objects come in many data types. Some data types are scalars, for example, FbxDouble1, FbxInteger1, and FbxBool1. Other data types have triplet (X, Y, Z) values that are stored as vectors.

FbxNode::LclTranslation is of type FbxDouble3, which is a vector with three elements. FbxAnimCurveNode is a container that can store the value of any FBX property irrespective of the data type. The member functions of FbxAnimCurveNode enables you to access the value of each element in a vector, for example, to get the value of channel X, the value of channel Y, and the value of channel Z.

#### See Also

- FbxNode::LclTranslation

- FbxAnimCurveNode::GetChannelCount, FbxAnimCurveNode::GetChannelValue, and related functions.

- fbxdatatypes.h, for a full list of FBX data types.