Focus Range: Production Ray Tracing of Depth of Field

Defocus blur adds realism to computer generated images by modelling the restricted focus range of physical camera lenses. It allows artists to draw the viewer's attention to in-focus regions of the image by separating them from the background. The widely used thin lens model provides a simple approach to achieve this effect, allowing artists to control the frame's appearance through the distance to the focus plane and the aperture size. Our proposed focus range model extends the focus distance to a range. This allows artists to keep characters fully in focus and independently define the out-of-focus blur. We demonstrate how to achieve this robustly in the presence of specular BSDFs, ray-oriented geometry and multiple light bounces. Additionally, we share our practical experience of integrating this model into our production renderer Glimpse.