A thermally and electrically conductive material is provided as a mixture of a dimethylpolysiloxane, metal flakes andor granules, a peroxide-based andor a dimethyl hexane based catalyst, PTFE powder and a platinum based fire retardant. Each hopper may be selectively removed and replaced without disturbing the other elements. The wheels, rings, or shapes are rotated, and at least one segment designator is provided to demarcate segments of each wheel, ring, or shape as an active segment when the wheels, rings, or shapes stop spinning. The display size of the obstacles varies based on the distance to the obstacles. An example includes controlling the population by examining indicia associated with rays returning from intersection testing, to be shaded, the indicia correlated with behavior of shaders to be run for those rays, such that population control selects, or reorders rays for shading, to prioritize shading of rays whose shaders are expected to produce fewer rays. The data eye path of the first serializer-deserializer is coupled to the second data path of the second serializer-deserializer.