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[Cartesian Coordinates System]   
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The Cartesian Coordinate System:

When working with 3D modeling and animation, measurement, distance and volume in space are determined by placement in width, height and depth, or the planes X, Y, Z. Using a Top, Front and side (left or right) view when constructing models, building a scene or moving cameras, lights and objects is standard. The Perspective and Camera views gives a view that simulates a "real" 3D environment.
Z is up.