Photometric calculations are carried out first, using Lighting Reality and DIALux, to establish the lux levels, uniformity, and glare control required for the space’s use — under BS EN 12464-1 for commercial and workplace zones, or against the layout and character brief for residential interiors. Only once the calculation is correct do we develop the layout in CAD and BIM, coordinated to the ceiling grid, partitions, and wider fit-out. Calculating before modelling means the layout reflects a design that’s already been verified, not one adjusted after the drawing is issued for coordination.