Clumped distribution in Vue ecosystems

What you will need to complete this tutorial

Software

This tutorial uses the following apps:

• The latest version of Vue. 
  You can download it on the Bentley Systems website. It is now free.

The problem with standard distribution

Here is an image using the normal Vue ecosystem distribution. It looks Ok, but the distribution of the ecosystem items is quite linear. The rocks are approximately the same size and distributed evenly on the terrain.

The same viewed from above. In real life it would clearly not look this way. Large rocks tend to break in smaller sizes and generate tiny bits of stone. These need to be close to the "seed". To be realistic we therefore need to create clusters of rocks of different sizes.

Creating the clusters

Fortunately Vue comes with an interesting feature to create such clusters: layer affinity.
Start from a terrain with the default material. CTRL click the material to edit it. Turn it into an ecosystem and follow these steps:

• Rename the ecosystem "Large rocks"
• Load the default stone in the ecosystem.
• In the density tab, choose a density of 15% and uncheck Decay near foreign objects.

That's all. But it is only the first layer.

You need to create additional ecosystem layers for the smaller rocks and they need to be above the existing one. 

Click the add layer button. When prompted to choose a material, hit escape. This will create a basic grey layer. Turn this layer into an ecosystem. Then delete the grey layer and retain the ecosystem.

You can then follow these steps on the new ecosystem layer:

• Rename the ecosystem to "Medium rocks"
• Load the default stone in the ecosystem.
• Change its size from 1 to .350
• Still in the General tab, modify the distribution by setting the affinity with the previous layer to 40%
• In the density tab, choose a density of 60% and uncheck Decay near foreign objects.
• In the scaling & orientation tab, choose a maximum size variation of 2.
• Check ou the settings of the environment tab.

You now need another layer for the smaller rocks. Use the same process to create the ecosystem layer. Make sure the layer is created above the medium rocks one. Then do the following on the new layer:

• Rename the ecosystem "Small rocks"
• Load the default stone in the ecosystem.
• Change its size from 1 to .1
• Modify the distribution by setting the affinity with the previous layer to 50%
• In the density tab, choose a density of 70% and uncheck Decay near foreign objects.
• In the scaling & orientation tab, choose a maximum size variation of 2.
• Check ou the settings of the environment tab.

You can now test the population. Start with the "large rocks" layer, then populate the "medium rocks" one and finish with the "small rocks".
You should have something roughly similar to this picture, looking like this from above: large rocks with groups of smaller ones around them. There should still be a fair amount of rogue ones.

Using clumped distribution with plants

The standard Vue distribution looks equally annoying with plants. Trees tend to grow in groups as they seed, not in a regular way as in this image. It almost looks like an orchard and there is no way to solve this issue with only one layer unless you push the density to 90% and fill all the terrain with trees or drive the density with a function, with sometimes unpredictable results.

Here is how it looks with clustered distribution. On this version, I use two ecosystem layers for the trees. The top layer has the following settings:

• Affinity: 50%
• Density: 150%