Bloom and glare

Bloom and glare are the halo and flare effects you notice when looking at a very bright light or reflection. Bloom is the soft, hazy glow that spills out around a bright spot. Glare usually shows up as thin streaks or star-shaped rays reaching out from the light. Neither actually exists in the scene; both happen inside a camera lens and in our own eyes, which is why render engines usually add them as post effects rather than tracing them.

Bloom and glare in architectural rendering

In night exteriors, street lamps, shop windows and lit interiors look far more convincing with a touch of bloom. Indoors, a faint halo around strong daylight coming through the glazing softens the mood of a room. The effect works hand in hand with tone mapping: if bright areas are not compressed properly, bloom turns into a grey, muddy haze.

Keeping it subtle

Overdo these effects and the image starts to look artificial, like a dream sequence. Star-shaped glare in particular feels cheap when every single lamp gets it. A modest intensity, a threshold that limits the effect to truly bright sources and a careful look at the final frame are usually enough. For worked examples of window light and night lighting, see our article on night exterior rendering.