iToo Software has recently shared a new guide to using Forest Pack’s altitude-based clipping and falloff when creating ecosystems that adapt to a terrain’s elevation. The tutorial covers the full process, giving tons of tips for beginners and advanced users.
Here is a small piece of the written version to get you interested:
Tip 1 – Use a small section for testing
First of all, when working with very large terrains it’s often easier and faster to use a small section of the landscape to help set up the Forest Pack objects that will define the ecosystem. There are several ways you could create a section of the landscape, you could for example select and clone a section of the terrain or add slice modifiers to isolate a selection, but we find it’s easiest to just draw a straight spline above the terrain to define a representative cross-section, and then use iToo Software’s free Glue Utility to project it onto the terrain. To do this:
- Draw a spline in the top view that overlaps a part of the terrain that represents more or less the full altitude range. I’ve included the island here too as that’s an important part of the composition.
- Move the spline so that it’s above the terrain then go to the Utilities tab and open the Glue utility. If you don’t have Glue, you can download it for free from iToosoft’s website.
- Use Glue’s Base Object picker to select the existing terrain object. If you want to follow the terrain more accurately, increase the Interpolate by Steps value. This will add more vertices to the spline before projecting it onto the terrain. Press Glue Selected to conform the spline.
- Now we need to turn this spline into a surface that Forest Pack can use. Do this by adding an Extrude modifier to the spline and using a negative amount to extrude downwards. Then, to add thickness, add an Shell modifier and increase the Inner or Outer amount until you get a small strip of land.
- Finally you should add a separate Plane object to represent sea level and you can then hide the original terrain so that you can work easily on this small section.
Tip 2 – Plan the ecosystem
It’s sensible to plan out your ecosystem in advance. In that way you avoid wasting time modeling or sourcing things that later are not required. In this scene we’re going to keep it quite simple. Along the bottom of the lake bed we will add some seaweed, nearer the river banks we want some reeds. In fact, we’ll add two types of reeds, tall ones that are largely above water level and smaller ones that poke above the water line and add some interest. Moving up as we get near the river bank we want some stones and pebbles that will transition into grass weeds and finally trees, rocks, and flowers.
With a plan in place you can easily create a Forest Pack object for each of the distinct areas straight away. Here’s a step-by-step example for creating the trees.
- Create a new Forest Pack object by setting the mode to Generate and picking the terrain cross-section object we created at the beginning of the tutorial.
- Go to the Geometry rollout and open the Library. Select the objects you want to import. For this example we’ll pick a Black Pine and an American Elm model from the new tree library included in Forest Pack 6. Note that you can select and import multiple objects at once by holding down the CTRL button as you click them.
- Adjust probabilities if necessary. In this example, we want fewer American Elms so the Probability setting for this model can be lowered to 20%.
- Go to the Distribution rollout and choose a distribution pattern from the drop-down list. We used Patches 1, one of several new maps included in Forest Pack 6.
- Adjust the Density values until you get the correct coverage of objects. In this case I’m using about 500m but it really depends on the scene and the objects being scattered so experimentation is a must.
You should do the same thing for all the Forest Objects in your ecosystem plan. To save you from having to read a lot of unexciting repetition we’re not going to show the creation of everyForest Objects. Throughout this tutorial, we’ll explain a principle and allow you to apply it yourselves. If you’d like to know more about the fundamentals of Forest Pack we recommend first following the Canal tutorial which will get you up to speed quickly, before tackling this tutorial.
As you can see, at this stage we didn’t worry too much about any other settings, only the choice of models, their probabilities and distribution. If you use Forest Pack’s built-in presets, like the new Layered Grass for example, you can probably use the default settings. In fact the scene mostly uses objects from the Forest Pack 6 library. Only the reeds and flowers are from a third party. If you want to follow the tutorial you will need to supply your models for these areas, or you could substitute them with the canes and daisies that come with the plugin.
Tip 3 – Restrict objects using altitude min and max settings
With all of the Forest Objects created we can restrict them to the elevation range planned in the first tip. This is made possible using the Limit by Altitude feature found in the Surfaces rollout. Using a simple Bottom and Top value you can restrict the scatter to a specific elevation range. We’ll take this one Forest Object at a time from the bottom to the top, starting with the seaweed:
- Open Forest Lister, click the Select all Forest Object button and then click the Lightbulb icon to hide them.
- We’ll enable the Forest Objects one at a time. Deselect all the Forest Objects using the button and unhide the seaweed Forest Object.
- At the moment the seaweed covers the entire terrain. We want it only on the lake bed. To enable this, go to the Surface rollout and enable Altitude Range > Limited.
- Adjust the Altitude Range > Bottom value until the seaweed is starting on the lake bed. You could leave this one because we want the weeds to go all the way to the bottom of the lake, but by narrowing the threshold so that it closely brackets the actual elevation range of the terrain, you will get more accurate results with Density and Scale falloff curves as we’ll see later. For this scene, a value of 14m worked well.
- Adjust the Altitude Range > Top value until the seaweed is stopping short of the shore. Don’t allow it to get too close to the shore or it will protrude through the water surface (although a little of this is OK because we can fix it later by editing the scale based on elevation information).
With those changes made you should have seaweed that is growing only on the bottom of the lake. Exactly the same technique is used to limit all the other Forest Pack objects used in this scene to create a complete ecosystem.