A new tool that I needed to consolidate, is an inverse square attribute by attribute. Ok, this I sounds bad. Let me start again.
The easiest way to create the density normally is by painting but there are some rules to follow, and more often than not, the shorter the hair the more density we have on those areas. And this rule can normally be automated. And we can create an attribute that is the inverse of our length to drive the density.
With this in mind, we worked on a new tool that is pretty much doing that, we take an attribute and create the inverse ( square ) of that attribute and rename it.
Basically, a density by length, or a length by density. Any attribute can be use, and technically any mesh can be combined!
Here you can see that the longer the hair the lower the value, and the shorter the hair the higher the value!
As density by length is a pretty common one we have a create length from curve toggle, just as it sounds. Connect the guides, activate the toogle and you will have the length attribute on your skin.
I will elaborate more on the options that we have but thats the general rule. One of the biggest issues are normally that when we send one attribute from some surfaces, it can get messy ( from curves for example ), so we are adding a blur operation. As density by length is a pretty common one we have a create length from curve toggle :D
As always, just the default value is not enough, so we are adding a basic ramps remap to control the range of the new attribute. By default a hard contrast exist to increase the main density on the shorter hairs.
A full attribute remap can be activate at the top menu to control the max and mix of the new attribute in case we need to settle for a minimun density or maximun value .