Graphics Reference
In-Depth Information
Figure 1.23.
Textured rectangular area light.
1.4 Implementation
1.4.1 Introduction
Multiple ideas from this chapter were combined and used as the basis of the light-
ing model in
Killzone: Shadow Fall
. The light rendering engine relies heavily on
real-time screen-space reflections and localized environmental reflection probes.
Both solutions could e
ciently support only radially symmetrical distribution-
based specular (Phong). One of the dynamic texture-based lights requirements
was to blend perfectly with existing image-based systems. Essentially we wanted
a capability to swap dynamic area light, with image-based light card, with cube-
map reflection at a distance without visual artifacts. We also wanted to support
analytical shape lights allowing the highest visual quality and advanced material
reflectance models.
1.4.2 Motivation
We used Cook-Torrance BRDF as the basis for our reflectance model. Normalized
Blinn-Phong was used as the distribution function. Fresnel and geometric terms
were calculated according to Smith-Schlick approximations [Schlick 94], matched
and normalized to Blinn-Phong. We also prepared a radially symmetrical version
of this BRDF. It was refitted to use Phong as the base, normalized and matched
as closely as possible to reference solution.
