Setup dialog Renderer panel Sampling Quality rollout
Note: The Sampling Quality
rollout appears only when the mental ray renderer is the currently
The controls on this
rollout affect how the mental ray renderer performs
antialiasing rendered images.
To use low sampling for previews:
- Leave the Minimum and Maximum values
at their default settings of 1/4 and 4, or reduce them to 1/16 and
TipDo not assign Minimum
and Maximum the same value.
To use high sampling for final renderings:
- Increase the Minimum and Maximum values
to 4 and 16, respectively, or to higher values.
TipDo not assign the same value to both Minimum
To view the sampling pattern:
- On the
rollout, choose Sampling Rate, then render
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.
Samples per Pixel group
Set the minimum and maximum
sample rates for antialiasing the rendered output.
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.
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.
TipFor most scenes the
Mitchell filter gives the best results.
- Box filter: Sums all samples in the filter
area with equal weight. This is the quickest sampling method.
- Gauss filter: Weights the samples using
a Gauss (bell) curve centered on the pixel.
- Triangle filter: Weights the samples using
a pyramid centered on the pixel.
- Mitchell filter: Weights the samples using
a curve (steeper than Gauss) centered on the pixel.
- 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.
Default=Depends on the
Filter type you choose:
- Box filter: Width=1.0, Height=1.0
- Gauss filter: Width=3.0, Height=3.0
- Triangle filter: Width=2.0, Height=2.0
- Mitchell filter: Width=4.0, Height=4.0
- Lanczos filter: Width=4.0, Height=4.0
Spatial Contrast group
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
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.
- R, G, BSpecify
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=(0.05,
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
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.
Introduces a variation into
sample locations; see
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
- 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,
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
- SpiralThe buckets
begin at the center of the image, and spiral outward.
- Left to rightBuckets
are rendered in columns, from bottom to top, left to right.
- Right to leftBuckets
are rendered in columns, from bottom to top, right to left.
are rendered in rows, from right to left, top to bottom.
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:
- Integer (16 bits per
channel)Outputs 16 bits per channel of color information.
- Floating-Point (32 bits per
channel)Outputs 32 bits per channel of color information.
This method supports high-dynamic-range imagery (HDRI). This is the default output format.
32-bit output is requred for lighting analysis.
When you render an
image with floating-point, 32-bit output, you might see jagged edges
in bright areas such as self-illuminated objects or reflections
of light sources. The reason is that in floating-point rendering,
the brightness of a pixel can be greater than 1 (“whiter than white,” so
Above: In a 16-bit
rendering, bright highlights are muted.
Below: In a 32-bit
rendering, bright highlights (on the lamp chains and the mirror),
are strong and jagged.
For example, suppose
a pixel is sampled four times, and an object occludes the pixel
one of those times. In a 16-bit rendering, this results in a 25
percent grayscale value for the pixel. The same thing happens in
a 32-bit rendering, unless the object is bright. In
that case, the pixel might be 20 times brighter than its surroundings,
so the result does not blend into its surroundings, and the rendered
highlight appears to be jagged or “aliased.” While this effect is
apparent in the 3ds Max Design Rendered Frame Window, it is only apparent:
if you use the image in a compositing program that handles HDRI
images, for example, or open it and adjust its levels in an image-processing
program such as Photoshop, the image appearance will be correct.