Two Calculation Methods

ElumTools can perform calculations by either Global Illumination or Direct Only methods. Global Illumination is the default unless Emergency Mode is selected (see below).

Direct Only - vs - Global Illumination

What's the difference? "Direct Only" means that only direct light from the luminaires to the calculation points (or surfaces) is considered in the calculation. Any light that would normally be reflected from one surface to another is not considered (imagine all surfaces as black). "Global Illumination" on the other hand considers all light that is reflected in the final accumulated solution at the calculation point based on color and reflectance (see Appendix A - Calculation Methodology).


Global Illumination Method Direct Only Method


Automatic Switch


The default calculation method for all program operating modes, with the exception of Emergency will be Global Illumination. When ElumTools is set to Emergency operation the calculation method will automatically switch to Direct Only if the software is in its default operating state. The default operating state will have the "Automatic" switch enabled (checked) in the calculation method menu.



Emergency Mode


When ElumTools is set to Emergency mode the calculation method automatically switches to Direct Only, why? Many emergency lighting codes require calculations to be performed using only direct light, that is light from the luminaires to the calculation points only. No reflected light is to be considered. This would be the most pessimistic case in a darkened area under emergency conditions.



If you would prefer to compute emergency results while considering reflected light, simply switch the calculation method to Global Illumination. The Automatic switch will then be disabled (unchecked).




Other Modes and Calculation Method


The Direct Only method can be used in General Mode and Emergency Mode only. Daylight and Horticulture Modes require Global Illumination. Only the Illuminance metric can be calculated in the Direct Only state. All other metrics require Global Illumination. Switching to other metrics on the toolbar will toggle the Calculation Method back to Global Illumination.