====== Forces ======
Forces are an additional level of manual control you can have over the procedural generation of a tree. They are objects that you place into a scene that allow you to manipulate the shape of branch spines. There are many types of forces, each with different actions and capabilities.

{{ ::force.jpg?400 }}

===== Adding Forces =====

To add a force to the scene, right-click in the tree window or use the "+" toolbar button and select "Add force." Forces can also be added from the Generation Editor's Forces icon. 

Since forces are world-space objects and not bound to the tree hierarchy, they can be transformed (moved, rotated, or scaled) with the gizmo in the [[tree_window|Tree Window]].

To delete a force, simply select it and press the DEL or BACKSPACE key.

===== Force Types =====

There are several types of forces available, each having their own unique affect on the tree shape. Any force can have its type changed by selecting a different type on the force's properties. The available types are:

{{:direction.png?nolink&35 |}}**Direction**\\
Branch spines grow in the direction that the arrow points.

{{:magnet.png?nolink&35 |}}**Magnet**\\
Branch spines converge on a single point at the center of the force.

{{:gnarl.png?nolink&35 |}}**Gnarl**\\
Branch spines twist around a world-space vector that is determined by the force's rotation.

{{:twist.png?nolink&35 |}}**Twist**\\
Branch spines twist along their local up vectors and are altered by the force's rotation.

{{:curl.png?nolink&35 |}}**Curl**\\
Branch spines curl inward on themselves in a direction determined by the force's rotation.

{{:plane.png?nolink&35 |}}**Planar**\\
Branch spines grow along a 2D plane determined by the force's rotation.

{{:force-return.png?nolink&35 |}}**Return**\\
Standard and subdivision branches will return to their original growth direction. Use this to keep wildly disturbed, jinked, twisted, curled, or gnarled branches under some control.

{{:force-seasonlight.png?nolink&35 |}}**Season light**\\
Leaves change [[Seasons|Season]] sooner based on the how much they are growing toward the position of this force object.

{{:direction.png?nolink&35 |}}**Season wind**\\
Leaves that fall on the ground due to Season are swept in the direction of the arrow.

{{::knockout.jpg?nolink&35 |}}**Knockout**\\
Anything growing in the direction of the arrow will be "knocked out," or removed. The "Strength" property controls how sensitive it is.

{{:mesh.png?nolink&35 |}}**Mesh**\\
Branch spines grow toward or around an arbitrary mesh object. See [[mesh_forces|Mesh Forces]] for more information.


===== Applying Forces =====

Forces are not always applied to every [[generators|Generator]]. The force must be enabled in the [[branch_generator#forces|Force Properties]] for it to have any effect. Due to this, one force can be set to act on the trunk (e.g., pull the tree left) and a different force can be set to act only on its child branches (e.g., pull the child nodes right).

> **Note**: If a generator is selected when you add a force, that generator will automatically have the new force enabled.

A generator's force properties also have values and curves that let you adjust how strong a particular force is when it affects the generator. This works in conjunction with the force's [[force_object|"Strength"]] property.


===== Attenuation =====
Since forces are world-space objects, they can be freely moved around in the scene with the transform gizmo when they are selected. By enabling the [[force_object#Attenuation|"Attenuation" properties]], the area of effect of the force will be limited to a radius around the force object. This lets you have a force affect on only a very specific part of the tree rather than the whole thing.

{{ ::force_attenuation.jpg?400 |}}

> **Note**: You can also limit a force to a certain area defined by a mesh by using the "Container force" properties. See the [[mesh_forces#container_force|Mesh Force documentation]] for more information.