Graphics Reference
In-Depth Information
were also useful for applying hair self-shadowing. Due to the nature of the self-
shadowing approximation calculation, there was no need to separate hair from
the engine's shadow maps when dealing with the environment casting shadows
on the hair because typically environment objects will be a large distance away
from the hair. The relatively large distance will generate a large number of fibers,
which will drive the shadow term to zero, as would be expected for a solid object
casting a shadow on the hair.
5.5 Antialiasing
After lighting and shadow calculations are completed, antialiasing calculations
occur for each hair pixel fragment. In this section, we explain the reasoning for
having specialized hair antialiasing. Then we will cover how the hair antialiasing
is performed. Lastly, we'll cover an alternative image-space approach we devel-
oped [Engel and Hodes 13,Lacroix 13], which we found to perform faster than
the geometrically based approach proposed by [Yu et al. 12].
Rendering individual hair strands can result in heavy aliasing issues. (See
Figure 5.5.) An individual hair strand will look like a jagged line once projected
into screen space. Also, with a large amount of hair strands, aliasing will not
only cause jagged hair strands, but there can also be noise among the final result
of shading a clump of hair strands. With hair, we can take advantage of special
geometry information and apply a specialized hair antialiasing to improve the
overall render quality.
An additional important benefit of the specialized hair antialiasing is to sim-
ulate the thinness of individual hair strands. Previous real-time hair rendering
simulations would run into issues where individual hair strands would appear
too thick. Applying the specialized hair antialiasing helps soften the edges of
With Antialiasing
No Antialiasing
Figure 5.5.
Here is a comparison of hair rendered with and without the specialized
hair antialiasing. The largest noticeable difference is the jagged staircasing present
in the image without antialiasing versus the softer hair edge pixels in the image with
antialiasing.
