Autodesk 12812-051462-9011 User Guide 3 - Page 1021

to 1.0, where 0.0 indicates the color component is fully unsaturated (black, or 0 in eight-bit encoding) and 1.0 indicates the color component is fully saturated (white, or 255 in eight-bit encoding). Default=(0.05, 0.05, 0.05). ■ A Specifies the threshold value for the alpha component of samples. This value is normalized, and ranges from 0.0 (fully transparent, or 0 in eight-bit encoding) to 1.0 (fully opaque, or 255 in eight-bit encoding). Default=0.05. ■ [color swatch] Click to display a Color Selector on page 391 to let you specify the R, G, and B threshold values interactively. Options group Lock Samples When on, the mental ray renderer uses the same sampling pattern for every frame of an animation. When off, the mental ray renderer introduces a quasi-random (Monte Carlo) variation in the sample pattern from frame to frame. Default=on. Varying the sample pattern reduces rendering artifacts in animations. Jitter Introduces a variation into sample locations; see Sampling on page 8112. Turning on Jitter can help reduce aliasing. Default=on. Bucket Width Determines the size of each bucket in pixels. Range=4 to 512 pixels. Default=48 pixels. To render the scene, the mental ray renderer subdivides the image into rectangular sections, or "buckets." Using a smaller bucket size causes more image updates to be generated during rendering. Updating the image consumes a certain amount of CPU cycles. For scenes with little complexity, smaller buckets can increase the rendering time, while larger buckets can make things render faster. For more complex scenes, the reverse is true. Bucket Order Lets you specify the method by which mental ray chooses the next bucket. If you are using placeholders or distributed rendering, use the default Hilbert order. Otherwise, you can choose a method based on how you prefer to see the image appear as it renders in the Rendered Frame Window. ■ Hilbert (best) (The default.) The next bucket chosen is the one that will trigger the fewest data transfers. TIP Always use Hilbert order when you use placeholders (see the Translator Options rollout on page 6316) or distributed rendering (see the Distributed Bucket Rendering rollout on page 6326). ■ Spiral The buckets begin at the center of the image, and spiral outward. 6276 | Chapter 20 Rendering