 Forced perspective was just one of the tricks used on the Helms Deep  "bigiature" to make it look like the real thing. Parts of the set  that were far away from camera were built to a smaller scale, to  make them look further away. The shots were also always made in  smoke to increase the sense of atmospheric distance.During the  design process, parts of the model were filled with Action Man dolls  to provide a scale reference.