Graphics Programs Reference
In-Depth Information
Anti-aliasing Contrast
Anti-aliasing Contrast values determine when mental ray
turns up the number of samples in a particular region of the frame. If the contrast
level from one pixel to its neighbor is below the threshold value, mental ray turns up
the number of samples for that pixel to render a higher-quality result. Therefore, the
lower
the values set here, the
higher
the sample rate will be (within the Min and Max
levels set).
Rather than setting high sample rates with just the Min and Max Sample Level attri-
butes, lower the Anti-aliasing Contrast value to force mental ray to use a sample rate
closer to the Max sample rate only where it needs to do so. You'll see this in action in
the next section.
Multi-Pixel Filtering Heading
When the Max Sample Level attribute is
set to a value higher than 0, filtering is done on the results of the sam-
pling of pixels to blend the pixels of a region together to form a coherent
image. A high filter size tends to blur the image, whereas low filter values
may look overly crisp. Box is the default filter and is the fastest to render,
whereas Gaussian (Gauss) gives a slightly softer result with the slowest
render times. Usually, render times don't vary much between different
filter modes—it's not as if Gaussian takes four times longer to render the
same frame over the Box filter type.
Sample Options Heading
The Sample Lock and Jitter attributes are
turned on to reduce noise and artifacts in rendered sequences with lots
of movement.
When you're ready to render your scene to disk, you still use Batch Rendering;
however, the options in the Batch Render Option window are different (Figure 11.33)
than they are for Maya Software.
Figure 11.33
mental ray Batch
Render options
Render Settings in Action!
In this section, we'll look at how Anti-Aliasing Contrast values and Number of
Samples work together to determine the quality of the render of a toy wagon. You
can find the scene (
RedWagonRenderSettings.ma
) to render in the RedWagon project
on the CD. This scene is set up to use Final Gather with an IBL using an HDR image.
We'll cover these methods later in this chapter.
The render quality settings are low at first (Min Sample Level of -2 and Max
Sample Level of 0 in Custom Sampling mode), with Anti-aliasing Contrast of 0.1
(default). This gives the render shown in Figure 11.34. You can see jagged highlights
on the wagon, especially the white lines on the side body, the reflections in the front
black nose, and on the back wheel.
