Graphics Reference
In-Depth Information
Figure 1.28.
Typical usage of textured area lights.
The area lighting model proved to be ecient on the next generation console
Playstation 4 GPU. The model itself is heavy on ALU operations (see Table 1.1),
which in our case helped to amortize waiting time for multiple texture fetches
from bandwidth intensive G-buffer and shadow maps. Therefore, we did not
experience a noticeable slowdown in comparison with more standard point-based
light models such as Blinn-Phong.
Unfortunately, several shortcuts we took during the model derivation resulted
in artifacts, under certain circumstances, when using Blinn-Phong-based BRDF
rectangular area lights. Due to those cases, we decided to use the rectangle
shape exclusively with Phong-based BRDF, which is a better fit for the used
approximations in the case of nonradially symmetrical light shapes.
Blinn-Phong Lights
Scalar ALU % Against Base
Point
222
0%
Sphere
252
+13%
Disk
361
+62%
Rectangle
382
+72%
Texture Rectangle
405
+82%
Tab l e 1. 1.
Comparision of Different light shaders assembly. Counts includes full deferred
shadowed light code.
