Hair and Fur tips

Hair segments 

The number of segments of each fiber can affect the render performance. In general terms, keep in mind these rules: 

• The more hair segments, the larger the RAM consumption, but the render will be faster if the hair is longer (as the bounding box of each segment can follow the hair shape more precisely, reducing unnecessary bounding boxes intersections). For shorter hair, increasing the segments beyond a certain value will not decrease the render time anymore and instead only increase the RAM usage unnecessarily.

• The less hair segments, the smaller the RAM consumption (as it involves less point information), but render time will increase for longer hair.

Creating transparency for hair using Layer masks

It is possible to use a Layer mask or simply changing the Layer weight from 100% to something lower, in order to make hair strands have a transparent look but be aware the render times will increase in this case. This only applies to Layer masks that completely start hiding the strands, if there is another Layer beneath that makes the hair strands opaque - the render times will not increase. This happens because there can be many overlapping transparent strands in this case.

It is really not necessary to make hair strands transparent to give the impression that they fade away because you can control the root and tip radii independently. Real strands of hair do not suddenly turn transparent, instead they can get thinner towards the tips and you can perfectly mimick this behavior with strand top radius alone.

To create a fading hair line so the strands don't appear as synthetic, you can map the root to tip with a texture map that is slightly brighter at the roots, which is also what can happen to real hair strands.