************ Introduction ************ Force Fields offer a way to influence a simulation, in example to add extra movement. :doc:`Particles `, :doc:`Soft Bodies `, :doc:`Rigid Bodies `, and :doc:`Cloth objects ` can all be affected by forces fields. Force Fields automatically affect everything. To remove a simulation or particle system from their influence, simply turn down the influence of that type of Force Field in its Field Weights panel. - All types of objects and particles can generate fields, but only curve object can bear *Curve Guides* fields. - Force Fields can also be generated from particles. See :doc:`Particle Physics `. - The objects need to share at least one common layer to have an effect. You may limit the effect on particles to a group of objects (see the :doc:`Particle Physics ` page). Creating a Force Field ====================== .. admonition:: Reference :class: refbox :Mode: Object Mode :Panel: :menuselection:`Physics --> Fields` To create a single Force Field, you can select :menuselection:`Add --> Force Field` and select the desired force field. This method creates an Empty with the force field attached. .. list-table:: Examples of Empty with the force field attached. * - .. figure:: /images/physics_force-fields_types_vortex_visualzation.png Vortex force field. - .. figure:: /images/physics_force-fields_types_wind_visualzation.png Wind force field. - .. figure:: /images/physics_force-fields_types_force_visualzation.png Force force field. To create a field from an existing object you have to select the object and change to the *Physics* tab. Select the field type in the *Fields* menu. .. note:: After changing the fields *Fields* panel or deflection *Collision* panel settings, you have to recalculate the particle, soft body or cloth system by *Free Cache*, this is not done automatically. You can clear the cache for all selected objects with :kbd:`Ctrl-B` :menuselection:`--> Free cache selected`. Particles react to all kinds of *Force Fields*, soft bodies only to *Force*, *Wind*, *Vortex* (they react on *Harmonic* fields but not in a useful way). Common Field Settings ===================== Most Fields have the same settings, even though they act very differently. Settings unique to a field type are described below. Curve Guide and Texture Fields have very different options. Shape Sets the direction which is used to calculate the effector force. For force fields from an empty object only *Point* and *Plane* shapes are available, as for a field from a 3D object there are additional *Surface* and *Every Point* options, and *Curve* for a field from a curve. Point Point with omni-directional influence. Uses the object origin as the effector point. Plane Influence only in the local Z direction. Surface The force field acts on a 3D object's surface. In this case, the Z axis is the surface normal. Every Point Uses every vertex in the mesh object as an effector point. Curve The force field acts along a curve object. Strength The strength of the field effect. This can be positive or negative to change the direction that the force operates in. A force field's strength is scaled with the force object's scale, allowing you to scale up and down the scene, keeping the same effects. Flow If non-zero, the effective force depends on the particle velocity. The value defines how quickly the effector force (acceleration) will be converted into the constant "air flow" velocity. Noise Adds noise to the strength of the force. Seed Changes the seed of the random noise. Effect Point You can toggle the field's effect on particle *Location* and *Rotation*. Collision Absorption Force gets absorbed by collision objects. Falloff ------- Here you can specify the shape of the force field (if the falloff *Power* is greater than 0). Falloff Type Sphere The falloff is uniform in all directions, as in a sphere. Tube The falloff results in a tube-shaped force field. The field's *Radial Power* can be adjusted, as well as the *Minimum* and *Maximum* distances of the field. Cone The falloff results in a cone-shaped force field. Additional options are the same as those of *Tube* options. Z Direction The force can be set to apply only in the direction of the positive Z axis, negative Z axis, or both. Power How the power of the force field changes with the distance from the force field. If *r* is the distance from the center of the object, the force changes with 1/*r*\ :sup:`power`. A falloff of 2 changes the force field with 1/*r*\ :sup:`2`, which is the falloff of gravitational pull. Max Distance Makes the force field affect other objects only within a specified maximum radius (shown by an additional circle around the object). Min Distance The distance from the object center, up to where the force field is effective with full strength. If you have a falloff of 0 this parameter will have no effect, because the field is effective with full strength up to *Max Distance* (or the infinity). Shown by an additional circle around the object.