EricMBloggie

The tutorial presents a method to simplify the sampling / anti-aliasing settings in Mental Ray to the point that you can use the Spatial Contrast number to control the ‘Speed vs. Quality’ of your renders. It is most closely related to Christopher Nichols’ anti-aliasing method for V-Ray, “Speed vs Quality in V-Ray,” but was developed independently from that, using countless websites and hours of testing. If you’re also a V-Ray user, I suggest shelling out the seven bucks for Nichol’s tutorial.

This method mitigates the time spent rendering an image with smooth, anti-aliased lines.

UGLY (Fast render)

NOT UGLY (Slow render)

Let’s get into it!

It all happens in the Renderer Tab under “Sampling Quality” when you are using Mental Ray.

A) Set Minimum to 1/64 and Maximum to 16.

The ‘Samples per Pixel’ area is where you tell Mental Ray the Min and Max range of how jagged versus how smooth to make a pixel.  This gives MR the ability to choose whether or not to pay extra attention to a pixel or not according to the Spatial Contrast (section C.)

You can get really nerdified about this sampling stuff at the LA Mental Ray User Group website.

B)  Set Filter to Mitchell

These filters act sort of like the different blurs in Photoshop.  You might already know that a box blur is faster than a Gaussian blur, but not quite as attractive to your eyeball.  If you want to know why it’s set to Mitchell, check this out:

The mental ray renderer provides five filter methods: Box, Gauss, Triangle, Mitchell, or Lanczos. Box, the default, is also the quickest. Mitchell is often the most accurate. The Box filter combines samples evenly, without weighting them. Each of the other filters uses a particular curve to weight samples before combining them.” (Max User Guide)

C) Contrast

We’re most concerned with the Spatial contrast, which relates to the difference in contrast of one pixel to another within your image.  As far as I’ve found, set the Temporal contrast to the same as the Spatial, if you’re doing an animation.  Temporal does not have anything to do with breaded, fried Japanese food, rather it deals with time, as in how MR deals with the anti-aliasing from one frame to the next.

Bring up a scene that you’re having trouble with.  Done?  Okay, good.  Now that you’ve set the scene up with the above settings, make the value of your Spatial Contrast .1.

Setting Your Spatial Contrast

Click the Color Box next to the [A] value of the Spatial Contrast area.  Using the Color Selector, [D in the reference image] change the Value (bottom spinner.)

Give it a render.  Pretty ugly, right?  Jagged edges all over the place.  Go down to .05.  Now your image will look slightly better.

Keep reducing your Spatial contrast until you find a balance between the speed of your render and the anti-aliasing quality.

Often times, a Spatial Contrast of .01 will look perfectly acceptable.  In some images, with a lot of detail, where you’re looking for very fine grain, you’ll have to reduce your Spatial Contrast to around .005.  Much lower than that, and you’re return on investment for render time won’t really pay off.  Sometimes, you can get away with your Spatial Contrast of .03.  It all depends on the image.

E) Leave this Alone

If you really want to find out what these settings do, read the manual, or go on a Google Hunt.

Any praise or problems?  Leave a comment!