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Vizard 8 » Tutorials & Examples » 3D models » Coordinate Systems » Tutorial: Querying Position

8.1

Tutorial: Querying Position

Key Concepts

• Retrieve a node's position within a given coordinate system with the <node3d>.getPosition( coordinateSystem ) method.
• When getting the position in a node's parent coordinate system, the modified offset encoded within the node's transformation matrix is returned.  When the position is retrieved in the global coordinate system, the node's transformation matrix offset is added to all of its parent's offsets to obtain the global position.  

Explanation

The next section gives some hard numbers regarding the position difference we can see between the pigeons by demonstrating the use of the getPosition method. Add and run the following code, then take a look at the output:

Calling getPosition without any arguments uses the default argument viz.ABS_PARENT (absolute parent) and retrieves the position offset encoded in the node's transformation matrix without any modification.  Notice that the value returned by getPosition is the same for both pigeons. When the first parameter of getPosition is supplied with viz.ABS_GLOBAL (absolute global) it returns the node's position relative to the global/world origin.  Thus, as we can see when we look at the world, childPigeon's global position is different than worldPigeon's.