A system and method for determining light illumination on a model in a virtual environment. A plurality of ambient cubes are defined in the virtual environment. A plurality of lights is detected. Indirect lights are also detected. Lights incident on the ambient cubes are divided into major and minor lights. For each ambient cube, six ambient cube values are calculated, each ambient cube value being related to the aggregate light illumination at a respective side of the ambient cube by the minor lights. The light illumination caused by the major lights is determined in real-time. The determined light illumination is modified by a value related to one or more ambient cube values associated with one of the plurality of ambient cubes.