Using Adaptive Super Sampling
In this tutorial we are going to demonstrate how to use Turtle's adaptive super sampling scheme. Lack of super sampling will lead to aliasing (flicker/jaggies/stair stepping) in animations and still images. But you shouldn't use higher super sampling settings than necessary since it can affect the render times.
Let's enable super sampling. The result is much better but not good enough.
- Min Samples: 1
- Max Samples: 8
- Contrast: 0.1
Advanced Edge Tracing: Off
- Min Samples: 8
- Max Samples: 8
A much better way to achieve the wanted result is to use Turtle's edge tracing features. Turtle will then identify edges in the scene and sample them more aggressively. The sampling rate is decided by the Forced Sampling Level attribute. 
- Min Samples: 1
- Max Samples: 8
- Contrast: 0.1
- Advanced Edge Tracing: Contrast
- Forced Sampling Level: 8
The result is almost as good as when we sampled 8/8, but we use a lot less samples. The image below illustates the sampling level. White means 8 an black means 1. The image is created by enabling the Diagonse Sampling Level setting. 
In the 8/8 case. We would have a pure white picture. The difference in render times in a test scene like this isn't really that great. But in a proper production scene the difference in render times can be huge.
Contrast versus Geometry
Turtle's edge tracing works in two different modes, Geometry and Contrast. Geometry edge tracing tries to find edges between different geometry objects. In our test scene, this means that the pipes will be edge traced, but not the shadows. The contrast mode super samples based on the contrast differences between neighbouring samples. Contrast super sampling is also very useful for reflection and refractions.
Choose your battles
Super sampling is a necessary tool to get great looking results. However, sometimes it is better to rethink your modelling approach. The left grid are made of geometry cylinders. The right is a plane with a grid texture as transparency map. The image is rendered with one sample per pixel. When texture sampling can be used, use it. It is always much more cheaper than super sampling.
