Our goal for this final project was to add some additional aspects of realism to the images rendered by the ray tracer through post-production effects, specifically the light bloom and lens flare effects. Lenses and mirrors inside the camera, and inaccuracies thereof, cause both of these effects in real photographs. Because viewers have come to expect these effects, a rendered scene without them can appear very unnatural.
There are several steps involved in the implementation of the light bloom effect. First, a copy of the rendered image is created. Then a bright pass filter is applied to this copy, emphasizing the bright areas of the image while de-emphasizing the dark areas. After this, the image is converted into greyscale.
In a perfect lens, the image is convolved according to an Airy disk. To approximate that effect, for a less-than-perfect lens, a Gaussian blur is used. In order to achieve sufficient blurring without spending too much time, a Gaussian blur with a radius of 20 pixels is applied to the image 3 consecutive times. After blurring, the copy and the original images are combined by adding the pixel color values together in order to create the final composite image with the light bloom effect.
In order to implement the lens flare effect, the location of the light to be used within the rendered image must be determined. This is accomplished in a manner similar to a shadow depth map lookup. A vector is created from the center of the image to the location of the light source to serve as the axis for the lens flare images. Each lens flare shape is defined in the XML file, and is then dynamically generated based on a relative position along the axis, a width, a color, and the type of shape.
Scence rendered normally:
After applying light bloom and lens flare:
