vlt_shaftlight

A shaft of light standing in the air, drawn on a cylinder with both faces kept and additive blending: the two walls of the tube add through the middle and thin to nothing at the silhouette, which is the read of a lit volume without a raymarch. y_bottom / y_top carry the vertical falloff of light entering from far above, shimmer drifts it, and soft fades it into whatever surface it meets so it does not cut a line across the floor. The cylinder it draws on should run past whatever caps the space above, so its flat end caps are behind geometry and never in frame — an additive tube whose cap the camera can see reads as a grey pipe. Consumed by vlt_shaft.