Bloom (shader effect)

Even a perfect lens will convolve the incoming image with an Airy disk (the diffraction pattern produced by passing a point light source through a circular aperture).

[3] When a photodiode is exposed to a very bright light source, the accumulated charge can spill over into adjacent pixels, creating a halo effect.

Current generation gaming systems are able to render 3D graphics using floating-point frame buffers, in order to produce HDR images.

To produce the bloom effect, the linear HDRR image in the frame buffer is convolved with a convolution kernel in a post-processing step, before converting to RGB space.

The convolution step usually requires the use of a large gaussian kernel that is not practical for realtime graphics, causing programmers to use approximation methods.

[10] Gaming Bolt described the trend as a gimmick that had died with the generation, and criticised the heavy use of the technique in major releases of the time such as The Elder Scrolls IV: Oblivion (2006), the Xbox 360 port of Burnout Revenge (2006), and Twilight Princess (2006).

An example of bloom in a computer-generated image (from Elephants Dream ). The light on the bright background bleeds on the darker areas, such as the walls and the characters.
An example of bloom in a picture taken with a camera. Note the blue fringe that is particularly noticeable along the right edge of the window.
Blooming in a CCD image