It is looked up in the shadow map to determine whether or not the point is in shadow, if it is in shadow a soft
shadow is generated using the shadow mask to modulate the texture value of the pixel, and then a final colour computation is carried out using the colour generated for the fragment by the rasteriser. Finally, at step S6, the result is
saved. The shadows, penumbra, colours etc generated by the fragment shader 238 use the shadow mask which has
been generated at step S3 to provide soft shadows in the final image, using the textured hierarchy described above.
In one embodiment, in order to render the image, the shadow mask is used in the computation of a form factor
in the following equation: