I built a Metal viewer on iPhone that re-lights an already-captured 3D scene with any lighting you like. Swap or rotate the HDR environment map, and the object's reflections follow in real time, with that environment also drawn into the background. Why relighting is valuable (the practical, commercial meaning) Ordinary Gaussian Splatting has the lighting from capture time baked in. So if you place the captured object somewhere else, the highlights and shadows clash with the new surroundings and