• Paints a sky-with-key-lights equirectangular environment into a width × height canvas, intended as input to IBL.setEnvironmentImage.

    Layout (top → bottom in equirect v):

    • sky band : cool blue zenith fading to a warm horizon.
    • horizon band : warm tan / peach — the dominant reflection colour for smooth metals and glass.
    • ground band : muted brown fading to a darker nadir.

    Three soft key lights at longitudes 0°, 120°, 240° sit ~30° above the horizon (warm, cool, amber tints), giving smooth-metal reflections recognisable bright spots without the architectural detail of paintStudio.

    Parameters

    Returns HTMLCanvasElement