@HG1: Thanks, I kind of came to that conclusion as well. So I wondered…how can I use position to influence scale without resorting to drivers (which I have never worked with in BGE)?
For my project I am trying to use the BGE as a control system for a Battlestar Galactica Viper. That way I can just fly the Viper around and then render the high quality Viper using Blender Internal or Cycles. So I wanted to link keypresses to thruster output. The thrusters are simply scaled cylinders that need to appear and fade away when keys are pressed and released. A continuous keypress means the thruster must stay on. Upon release the cylinder should fade out.
What I ended up doing was to use BGE scripts to move black sphere based brushes to the surface of a blue canvas, thus leveraging the Dynamic Paint system. But you say….Atom, Dynamic Paint does not work in the BGE. Remember, I am going to use a non-BGE system for rendering. The BGE records the simulation and position of the brush. After your simulation is completed, switch to Blender Render mode and bake the Dynamic Paint cache. The canvas emits a single hair particle with a display type of object, a cylinder image mapped with a flame. The proximity of the sphere to the canvas generates a vertex map that is mapped to particle length. So when the sphere is close, the hair is long. When the sphere is missing, Dynamic Paint start to cool off the vertex map, thus shrinking the cylinder. After all these steps I can control scale from the BGE via keypresses.
In this attached scene I am using the low poly viper model by Henry Tracey as the control cage for the game piece.
To view the results, pull down the BLEND file and bake all caches (takes about 3-4 minutes on my system). Then press play and observe the thruster cylinder generation. To try your own flight press P-KEY over the 3D viewport and used the keys, AWDSQE to control the 6DOF of the viper. When done a bunch of large cylinders will crowd the viewport. Ignore them and immediately bake the cache to see your new flight thrusters.
26_cc-by_viper_mk2_control_RIG.blend (806 KB)