Raytracing and Analyses Support

Suggestions for Raytrace Settings

Since Photopia is a probabilistic based raytracing program, the results get more accurate as more rays are traced. The number of rays that are required to obtain accurate results depends on the level of "resolution" you have specified, in other words, the level of detail in the results. You can view the results such as the candela polar plot and the illuminance plane shaded plot and watch as they vary around their final values with each update as the raytrace proceeds. The default update frequency is 10%, so you see results at 10%, 20% and so on until the raytrace is finished. The least detailed result is the luminaire efficiency (LOR). This is a single number that represents how many lumens exit the luminaire compared to how many lumens were generated by the lamps. The exact direction of the exiting lumens is not critical when determining the efficiency. Thus, you can see that the efficiency changes very little after the first update of the results during the raytrace. The candela distribution requires much more detail to be resolved since Photopia needs to determine exactly how many lumens belong in all of the angular zones of the distribution. The more angles that are specified in the distribution, the smaller the angular zones and thus the more rays it takes to determine the correct proportions of lumens in all zones. The most level of detail is generally required for the illuminance planes. Whereas the angular zones in the candela distribution might be separated by 2.5 or 5 degrees, the small patches in a high-resolution illuminance plane might be separated by fractions of a degree in angular spread. With this general understanding, we make the following recommendations for the Raytrace and Photometric Output settings. Keep in mind that these are only general recommendations and you can vary these values as long as you understand the consequences.

Raytrace & Photometric Output Setting Recommendations

Applications	Photometry Type	# of Rays - Initial Evaluation	# of Rays - Final Evaluation	# of Reflections - No Lens	# of Reflections - With Lens	Vertical Angle Increment	Horizontal Angle Increment
Wide Beam	C	500,000	5,000,000	15	25	5	15
Narrow Beam	C	500,000	5,000,000	15	25	2.5	15
Very Narrow Beam	C	500,000	5,000,000	15	25	1	15
Roadway or Area Light	C	2,500,000	10,000,000	15	25	5	5 or 10
Wide Beam Floodlight	B	2,500,000	10,000,000	15	25	5	5
Very Narrow Beam	B	2,500,000	10,000,000	15	25	2.5	2.5

*Note: When using CFL lamps, we recommend that you turn ON the Lamp Shadow Check option. This options can be left off for most other lamp types. All other raytrace settings can generally be left at their default values.

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