Graphics Reference
In-Depth Information
version of the Montecarlo render. In addition, the render time difference between 256 rays and 2,048 rays
is only a multiple of three, whereas the same change in rays for the Montecarlo renderer was nearly eight
times longer.
Figure 7-37:
Because of the intelligent sampling methods of Irradiance Caching, the renders start off much
smoother and are completed much faster.
Improvements can still be made to enhance the image quality. To do this, you will look at the next group
of settings. Irradiance Rate and Irradiance Ratio work together. The
Irradiance Rate
sets the minimum value
for distance between sampled pixels, and the
Irradiance Ratio
is multiplied by the Rate to get the maximum
distance between sampled pixels. To understand this, a little explanation of Irradiance Cache rendering is
necessary. You may notice that when a render is initiated with Irradiance Caching on, it will first launch a
series of pre-passes (four in total). These passes will sample the image at full quality (based on the Irradiance
Rays), and then the Rate and Ratio kick in to decide where more light samples are needed. The averaged
values are used to fill in the pixels between the cached pixels. In areas where there is little detail, the pixels
will be sampled from a broader area and result in faster render times. Areas of higher detail will draw from
closer high-quality samples and result in good detail and slower renders. The last value for most images is
the
Interpolation Values
field. This defines the maximum number of pixels that can be sampled to create
the finished pixel. Increasing this number will smooth the render and result in slightly slower render times.
There is a balancing act between these settings that will vary from image to image. In most cases, the
default settings will be a good starting point.
Figure 7-38
shows the difference between the default render
and the settings of 512, 0.5, 12, and 4 for Rays, Rate, Ratio, and Interpolation Values, respectively.
Figure 7-38:
Default Irradiance Cache settings (left) can be greatly improved upon with a little tweaking
(right).
