Rendering menu > Render > Render Scene dialog > Renderer panel > Sampling Quality rollout
Main toolbar > Render Scene > Render Scene dialog > Renderer panel > Sampling Quality rollout
Note: The Renderer panel appears only when the mental ray renderer is the currently active renderer.
The controls in this rollout affect how the mental ray renderer performs sampling.
To view the pattern of sampling:
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On the Diagnostics rollout, choose Sampling Rate, then render the scene.
Instead of rendering the image, mental ray draws a diagram that shows the range of applied sampling values. White lines indicate edges in the scene, where the mental ray renderer took the maximum number of samples. If fractional sample limits are used (sampling down), lighter dots indicate the higher value while darker dots indicate the lower value.
To assist with analysis, View Samples also draws red lines around each bucket, or separately rendered block.
When the Minimum and Maximum number of samples are equal, the diagram shows all buckets as white.
Set the minimum and maximum sample rate.
Minimum—Sets the minimum sample rate. The value represents the number of samples per pixel. A value greater than or equal to 1 indicates that one or more samples are computed per pixel. A fractional value indicates that one sample is computed for every N pixels (for example, 1/4 computes a minimum of one sample for every four pixels). Default=1/4.
Maximum—Sets the maximum sample rate. If neighboring samples find a difference in contrast that exceeds the contrast limit, the area containing the contrast is subdivided to the depth specified by Maximum. Default=4.
The values of the Minimum and Maximum lists are "locked" together so that the value of Minimum can't exceed the value of Maximum.
Filter type—Determines how multiple samples are combined into a single pixel value. Can be set to Box, Gauss, Triangle, Mitchell, or Lanczos. Default=Box.
Tip: For most scenes the Mitchell filter gives the best results.
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Box filter: Sums all samples in the filter area with equal weight. This is the quickest sampling method.
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Gauss filter: Weights the samples using a Gauss (bell) curve centered on the pixel.
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Triangle filter: Weights the samples using a pyramid centered on the pixel.
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Mitchell filter: Weights the samples using a curve (steeper than Gauss) centered on the pixel.
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Lanczos filter: Weights the samples using a curve (steeper than Gauss) centered on the pixel, diminishing the effect of samples at the edge of the filter area.
Width and Height—Specify the size of the filtered area. Increasing the value of Width and Height can soften the image, however it will increase rendering time.
This control sets the contrast value used as thresholds to control sampling. Spatial contrast applies to each still image.
If neighboring samples in a frame differ by more than this color, the mental ray renderer does recursive supersampling (that is, more than one sample per pixel), up to the depth specified by the Maximum samples per pixel value. Increasing the Spatial Contrast values decreases the amount of sampling done, and can speed the rendering of a scene at the cost of image quality.
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R, G, B—Specify the threshold values for the red, green, and blue components of samples. These values are normalized, and range from 0.0 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=(0.051, 0.051, 0.051).
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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.
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Color swatch—Click to display a Color Selector to let you specify the R, G, and B threshold values interactively.
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. Turning on Jitter can help reduce aliasing. Default=off.
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.
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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) or distributed rendering (see the Distributed Bucket Rendering rollout).
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Spiral—The buckets begin at the center of the image, and spiral outward.
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Left to right—Buckets are rendered in columns, from bottom to top, left to right.
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Right to left—Buckets are rendered in columns, from bottom to top, right to left.
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Top-down—Buckets are rendered in rows, from right to left, top to bottom.
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Bottom-up—Buckets are rendered in rows, from right to left, bottom to top.
Frame Buffer Type—Lets you choose the bit depth of the output frame buffer: