Hi folks, a tutorial for populating a terrain relistically using only one tree and one image. The tutorial starts

off quite detailed & then gets faster as you're essentially doing the same thing over again but for different

effects.

OK, to start off here's the image that will drive the tutorial's filters:



and we can simply map in onto the terrain (any terrain, make it smooth & low, & enlarge it somewhat). This isn't

really necessary, but we need to see if the trees grow in the right place so it's handy:



We make the terrain's material into an Ecosystem material & add a tree. Feel free to change or add trees. As you

can see the image you applied to the terrain is now it's underlying material:



Now, on the Density tab of this window, click the Variable Density box and when the sphere becomes available for

editing, right click it and choose Edit Function. You will now add a texture Map node, you can see which one it is

on the left hand side here. This node will automatically have a UV input node, don't worry about it, it just makes

sure the image fits the terrain. Add the image to the node in the usual way that images are added in Vue:



With this setting you can see the default filter...:



...produces this default density distribution:



You can see that it's pretty much well foliaged, except for the very blackest areas which have less foliage

density. So right-click the filter and choose Edit Filter, add some keypoints to it, click that wavy line icon in

the top right corner (this makes the filter curve, erm, curvy ) and just muck around with it:



Each time you change it, OK it and repopulate the terrain & see its effect. You're trying to arrange it so the

very blackest areas have no trees, while the very whitest areas have maximum trees, and the shades in between have

in-between densities. You might spend an hour or so here alone, if you're not used to it so don't worry about it.

You can see my curve, try & get a similar one, it should work fine assuming you're using the same image as me.

Eventually you will get a tree population that looks like this:



As you can see the filter curve seems to be having the desired effect. Now we would like to alter the scale of the

trees, based on the same image. We would like trees that are densly packed to be smaller than trees that have more

room, so we can use the same texture node to drive the Scaling output node in the function editor. In the Scaling

tab on the window, click the Variable Scaling box so again the sphere becomes editable, then right-click it and

choose Edit Function in exactly the same way as we did with the density:



Drag a connection from the Scaling output node to the Texture Map node. If we leave the connection as is we

actually get the reverse of what we want, densly packed trees being bigger etc so we can add an Opposite node

filter onto the connecting line as shown. Simply click the filter node icon there on the left and then change the

node type to Opposite with the drop-down list. You would have noticed this for yourself, I'm just saving you some

time. So now, by adjusting the Size filter:



To appear somewhat like this:



And repopulating the terrain we get a distribution similar to this:



As you can see it's already quite nice & realistic. There is still some size variance in there outside of our

filter control, we could change that as well but let's leave the extra random quality there for now.
In the Colour tab, do The Thing and add the Colour output node to the Texture Map node's ever increasing list of

outputs (I think you might get a choice of whether to add the connection to a colour output or a greyscale output.

I think I chose greyscale):



Now we are going to change the colour of the trees based on the texture map as well. Here you can choose the

colours that make up the colour range using the colour gradient window there (right click the window, choose

whether to load a colour gradient or to make your own up) and you can play with the filter above to drive the

colour distribution across the texture map range:



After a while of fiddling about you might end up with a population simlar to this:



The trees in this tutorial aren't very realistically coloured, but it serves to illustrate well so I left them

fairly cartoony. Now we should really change the Underlying material we noted before, so find it, right-click the

sphere & choose Edit Material. Make it a mixed material, load some sort of grassy texture as Material 1 and

whatever material you want your paths to be made out of for Material 2. I chose Brick Wall. Add the image texture

to drive the distribution (the function editor is used for this again) and fiddle with the filter so only the

blackest areas get the brick wall material:



If all goes well you should have a serene garden type scene like this:



I hope those of you who wanted a tutorial have gotten something out of this, no doubt there are some mistakes etc

waiting to trap you but most of all I hope you can sort of see what the filters can do. I still am not very

comfortable with them, one thing they definately need is labelled axis so I know what I'm mapping against what.