What is an Abiotic Factor?
Ever heard this term before?
According to National Geographic:
"An abiotic factor is a non-living part of an ecosystem that shapes its environment. In a terrestrial ecosystem, examples might include temperature, light, and water. In a marine ecosystem, abiotic factors would include salinity and ocean currents. Abiotic and biotic factors work together to create a unique ecosystem."
Source : https://www.nationalgeographic.org/topics/resource-library-abiotic-factor/
In other words, the abiotics are all terrain features that can influence your scatter-system(s), they are essential to give credibility and realism to your virtual world. Especially if you are scattering a natural landscape scene!
Elevation
The abiotic elevation feature will remove instances above or below a certain altitude threshold. You can control minimal, maximal, both transitions and denstity/scale influence.
Use-case:
When scattering a forest that covers large areas of your landscape, you can assign elevation rules such as fewer & smaller trees on higher altitude. In the real world depending on the oxygen level the probability of having various tree species differs..
The threshold value can be represented as a percentage unit, based on the minimal/maximal vertex location of your surface mesh found, or in a altitude unit, where the altitude is sampled from the chosen context space.
If you'd like your altitude effect to stay consistent across many surfaces, we advise to choose the global space method with the altitude unit method.
Slope
The abiotic slope feature will remove instances above or below a defined slope threshold. You can control minimal/maximal transitions and their denstity/scale influence.
Use-case:
Some plant species will not be able to grow on steep terrain, adding a slope rule in your scatter is an essential tool to have at your disposal.
It can also be quite handy to define flat scattering areas for scattering cities or villages for example.
Orientation
The orientation border feature will remove instances depending on how similarly aligned the instances normal are compared to a chosen direction.
Use-case:
Add moss on rocks, distribute plants species on slopes that receive more/less sun.
Local vs Global
Here on the left we can see an orientation factor based on the local surface space, on the right, based on global world space.
Curvature
The abiotic curvature feature will remove instances depending on the concavity / convexity of your surface(s).
Note that this feature might be too sensitive for too noisy terrains. As the curvature data is calculated in real-time, you might experience slowdowns when using highpolysurfaces.
Border
The abiotic border feature will remove instances near the border of your surfaces boundary-edges. You are able to control the distance/transition distance.
Use-case:
When scattering large clumps of grass, it can be difficult to achieve clean delimitation near borders, use this feature to remove the clumps of grass whose origin stands too close to the surfaces boundaries.