A computer graphics method and apparatus allows designer control over the rendering of objects and scenes, in a rendering system using ray tracing for example. In one embodiment, the interferometer includes a translucent body having a first portion and a second portion, where the second portion has at least three internal reflective sides. The level of the amplified probe signal at each of the pump power levels for the plurality of pump wavelengths is measured. The chloride ion concentration of second aqueous fluid in the holding tank is measured by a chloride ion specific sensor in probe housing, which sensor is in electrical contact with microprocessor. In use the optical MEMS switch may be integrated with other optical components to form planar light circuits. In some embodiments, the process may include selecting the ebullated bed pitch hydrocracking reactor reaction conditions to be at or below the level where sediment formation would otherwise become excessive and prevent continuity of operations.