Antialiasing is one of the most important things for good digital produced images or animations.Vray has one of the best and most robust AA solutions available. In VRAY the antialiasing again is not just a thing that gets applied after shading but the whole engine is connected to the image and DMC Samplers.

The same power that gives the GI engine its quality is also used for Images sampling. Therefore sometimes image sampling (Antialiasing) is used in vray also to support GI and glossy reflections. so all setup is party connected, specially the adaptive DMC method.

Why do we need AA in renderings? - in real word cameras or in the human eye the light goes through more or less perfect lenses. those lenses and also the air filter the light and compensate extreme contrast between near points. also analog methods are not bound to pixels and therefore do not have to problem of pixel stepping when images do not have enough resolution or of very tiny and fine structures have to be rendered.

Vray can render ultra fine lines, by oversampling an image in an intelligent and still fast way. for areas that don`t need much antialiasing vray can use under sampling - negative values - at the same time, depending on the method, this highly adaptive AA can give ultra crisp and still still soft results at reasonable render times. i believe one aspect of the high image quality in vray is not only the great GI engine but also the wonderful AA quality.

In vray you can use values like 100x AA with Adaptive DMC Sampling (with universal setting p.e.) and still get ok render times. such extreme values wont be used all time, but they show the power behind. still high settings like 4x16x can be used at ultra high speeds for superb image quality. also i noted that images with good AA can be scaled up much better than “normal” 3d images, so it might pay to invest in learning the AA engine and use good quality settings.

In VRAYforC4D, an image sampler refers to an algorithm for sampling and filtering the image function, and producing the final array of pixels that constitute the rendered image.

VRAYforC4D implements several algorithms for sampling an image. You can choose between Fixed rate sampler, Adaptive DMC sampler and Adaptive subdivision sampler. Which is the fastest depends very much on the scene and on the settings of GI, Materials etc.

Image sampler

Type - specifies the image sampler type:

• Fixed rate sampler - this sampler always takes the same number of samples per pixel;
• Adaptive DMC sampler - this sampler takes a variable number of samples per pixel depending on the difference in the intensity of the pixels;
• Adaptive Subdivision sampler - this sampler divides the image into an adaptive grid-like structure and refines depending on the difference in pixel intensity.

Fixed rate sampler

Fixed rate sampler - this is the simplest image sampler, and it takes a fixed number of samples for each pixel.

Subdivision - determines number of samples per pixel. When this is set to 1, one sample at the center of each pixel is taken. If this is greater than 1, the samples are distributed within the pixel. The actual number of pixels is the square of this parameter (e.g. 4 Subdivisions produce 16 samples per pixel).

Note: that due to clamping of samples to the [black, white] range for the RGB color channel, sometimes this sampler can produce darker results when used with blurry effects. The solution in this case is to increase the Subdivisions for the blurry effect, or to use the Real RGB color channel.

Adaptive Subdivision sampler

Adaptive Subdivision sampler - this is an advanced image sampler capable of under sampling (taking less than one sample per pixel). In the absence of blurry effects (direct GI, DOF, glossy reflection/refraction etc) this is the best preferred image sampler in VRAYforC4D. On average it takes fewer samples (and thus less time) to achieve the same image quality as the other image samplers. However, with detailed textures and/or blurry effects, it can be slower and produce worse results than the other two methods.

Also note that this sampler takes up more RAM than the other two samplers - see the Notes below.

Min. rate - controls minimum number of samples per pixel. A value of zero means one sample per pixel; -1 means one sample every two pixels; -2 means one sample every 4 pixels etc.

Max. rate - controls maximum number of samples per pixel; zero means one sample per pixel, 1 means four samples, 2 means eight samples etc.

Jitter- displaces the samples slightly to produce better antialiasing of nearly horizontal or vertical.

Threshold - determines the sensitivity of the sampler to changes in pixel intensity. Lower values will produce better results, while higher values will be faster, but may leave some areas of similar intensity under sampled.

Object outline- this will cause the image sampler to always super sample object edges (regardless of whether they actually need to be super sampled). This option has no effect if DOF or motion blur is enabled.

Material ID- uses the material id pass (change of material) to antialiasing the transition from one to the next material on surface.

Normals- this will super sample areas with sharply varying normals. This option has no effect if DOF or motion blur is enabled.

Normals threshold- this will super sample areas with sharply varying normals. This option has no effect if DOF or motion blur is enabled.

Z-Value- uses the z-depth pass (change of depth) to super sample the areas where a sudden depth change occurs.

Z-Value threshold- adjusts the threshold of the above depth sampler.

Show samples- if this is on, VrayC4D will show an image where the pixel brightness is directly proportional to the number of samples taken at this pixel. This is useful for fine-tuning the antialiasing of the image.

Antialiasing filter

Antialiasing filter

Antialiasing filter - various filter can be applied, there are sharpening methods and blurring filters, depending on what you need, for still images you might want to use sharpen filters, for animation make sure to use soften filters. Note that rendering with a paricular filter is not the same as rendering without a filter and then blurring the image in a post-processing program like Adobe Photoshop. Filters are applied on a sub-pixel level, over the individual sub-pixel samples. Therefore, applying the filter at render time produces a much more accurate and subtle result than applying it as a post effect. VRAYforC4D can use this filters:

Box	Also known as nearest neighbour filter. Applies an internal 1x1 pixel box filter
Disc	XXXXX
Triangle	XXXXX
Welch	XXXXX
Parzen	XXXXX
Hann	XXXXX
Blackman	XXXXX
Lanczos	A high quality filter that fully compensates blur effects and also reduces any kind of moire pattern.
Sinc	XXXX
Mitchell-Netravali	Does some mild sharpening to compensate for blur effects, allows control between edge-enhancement and blurring
Area	Blurrs the image, visually more pleasing than the box filter.
Catmull-Rom	Edge-enhancing filter, often used for architectural visualizations. Note that edge enhancing can produce "moire" effects on detailed geometry.
Gaussian	A multy purpose blur filter. Alpha/opacity channels are internal always resampled by using this filter.

Checkit to fill info about filters in future
http://www.spot3d.com/vray/help/150SP1/examples_image_sampler.htm
http://wiki.blender.org/index.php/Doc:FR/Manual/Render/Oversampling_(Antialiasing)
http://rise.sourceforge.net/cgi-bin/makepage.cgi?Filtering
http://www.blender.org/development/release-logs/blender-240/samples-and-filtering/

Notes

Which sampler to use for a given scene? The answer is best found with experiments, but here are some tips:

• For smooth scenes with only a few blurry effects and smooth textures, the Adaptive subdivision sampler with its ability to under sample the image is unbeatable.
• For images with detailed textures or lots of geometry detail and only a few blurry effects, the Adaptive DMC sampler performs best. Also in the case of animations involving detailed textures, the Adaptive subdivision sampler might produce jittering which the Adaptive DMC sampler avoids.
• For complex scenes with lots of blurry effects and/or detailed textures, the Fixed rate sampler performs best and is very predictable with regards to the quality and render time.
• A note on RAM usage: image samplers require substantial amount of RAM to store information about each bucket. Using large bucket sizes may take a lot of RAM. This is especially true for the Adaptive subdivision sampler, which stores all individual sub-samples taken within a bucket. The Adaptive DMC sampler and the Fixed rate sampler on the other hand only store the summed result of all sub-samples for a pixel and so usually require less RAM.
• You should have at Color mapping tab Clamp output set to 1.5 or 2 if you have enabled Subpixel mapping on at same time. if you set Clamp output to 1 it might be too low and result in problems in AA.