photometrics

Real luminaire light distributions, from the measurements manufacturers publish.

A fixture does not emit evenly. Its maker measures how much light leaves it at each angle and ships the result as an IESNA LM-63 file — a grid of candela values over vertical and horizontal angles. Architectural and product work is lit from those measurements rather than from a cone with a soft edge, because the shape of the falloff is what makes a fixture read as that fixture.

ies reads such a file and rasterizes its vertical distribution into a layer of the shared feature-texture array. A spot light pointed at that layer through cookieLayer then projects the distribution through its own cone: angle from the axis becomes radius in the image, and candela becomes brightness.

That needs no new engine capability. The cookie projection already exists; what this package adds is the reading of the file and the rasterizing of its curve.