Depth of Field Quality Adjustment in mental ray

Written December 6th, 2010
Categories: Articles, Rendering / Compositing
4 comments

In this quick article, we’ll be visually exploring how to adjust the quality of the depth of field effect in 3d Studio Max with mental ray.  The process is closely tied with how you increase the quality of your render (sampling).  All you have to do is increase your render sampling to smoothen the depth of field effect. Once you’ve had some practice, you’ll know just how to adjust your render to get great results every time.

Let’s begin with my warehouse sample scene.  There are several aspects of the scene that make it perfect for testing depth of field.

  1. There are numbers around the scene that represent a distance from the camera in feet.  ”2″ is 2 feet from the camera, “4″ is 4 feet from the camera, etc.
  2. There are lots of detail around like girders and windows that will accentuate any blurring effects.
  3. The floor and wall have a checker pattern that is 1-foot by 1-foot squares.  They also help us understand the blurring effect.
basic render of the warehouse

This is a basic render of the warehouse scene. Not great.

We can do better than this, but let’s set up our depth of field effect first.  Once we get an effect we like, we can improve the quality.

Select the camera, and engage the depth of field (mental ray) effect.

engage-depth-of-field-mental-ray-camera

Engage the effect.

When we take another render, we can see that some elements have gotten blurry.  With a target distance of 32 feet, we can see the number “32″ clearly, but the number “2″ is blurrier.

warehouse-render-dof

Warehouse render with default depth of field.

Notice that the image is still pretty grainy, and we’re even getting sampling artifacts on the tile flooring and garage doors.  Let’s improve our render sampling and get a comparison to see how we can improve the quality.  The most direct way to improve the quality is to increase our sampling from {1/4 and 4} to 1 and 16.  We’ll also want to use a better filter type.

increased-render-sampling

Increased render sampling and using a better filter.

Below you can see the new render plus a comparison of key areas before and after the Samples per Pixel change.

warehouse-fine-render

A finer render of the warehouse.

A clear improvement in details.

The depth of field effect improved, too.

Now there’s a catch to all of this.  The original render only took 2:41 while the finer render took 6:53.   Remember not to turn up your depth of field quality settings until you’re ready to take a final render!

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