Patches of particles (hair) on a plane following noise

Question

I'm trying to make underwater reeds for a scene in Blender cycles.

I have my reeds textured and ready, I'm using a particle system as a hair type and I've set it up so the "grass" covers my floor plane.

My problem is the grass is spread evenly across the plane. I want them to be in patches, clumped together and have the floor visible where they're absent.

A solution in my head would be for the particles to follow a noise node, tightened up using a colour ramp but I cant seem to figure this out, if it's at all possible?

Thanks for your help

Answer 1

The method I would use to clump the vegetation together is by tweaking the 'radius' value in the particle's children tab. Note that children type must be set to 'Simple'.

This is the most simple and easy way to achieve the 'bush' look, but if you want more freedom and customization possibilities, a density texture is the way to go!

For example: I'm using a cloud texture to control where the hair can grow and where not.

For this example I'm using a cloud texture, but you can obviously paint a texture by hand and gain 100% control.

Make sure to check the influence of your texture:

And assign it in the particle system as well:

A fundamental difference between these methods is that by using a texture, you're actually 'cutting' out portion of your scattered hair. By using the radius option under the children's panel, you control where the hair-particles are going to be scattered. So your amount of particles in the settings will be higher when using a texture.