Forces make simulated objects move according to different types of forces in nature. There are nine types of forces you can apply to simulations: gravity, wind, fan, drag, attractor, vortex, toric, turbulence, and eddy.
Each force is represented in the scene by its own control object, which you can select, transform, rotate, and scale like any other object in the scene. For example, you can change and animate the fan’s direction, or you can even defy the laws of physics by inverting the gravity control object’s direction so that it’s pointing up instead of down.
Each particle cloud, hair object, rigid body object, cloth object, or soft body object can have multiple natural forces applied to it. As well, you can have the same force applied to a number of particle clouds or hair, cloth, and soft-body objects in a scene.
With rigid bodies, a force is applied to a simulation environment as soon as you create it, and affects all elements within it—see The Simulation Environment.
If you’re working with particles, fluid, or explosions, you apply forces to its particle cloud. This means that if you have multiple emitters for one cloud, changing the force will affect them all. However, you can control a force’s effect on each particle type set up for each emitter from its Envir. property page (see Setting Up Forces for Each Particle Type), which means that each particle type can react differently to the same force that is on the cloud.
As well, you can control the effect of each force on hair (see Setting Up Forces for Hair) and cloth (Setting Up Forces for Cloth).
This table shows which type of force works with which type of simulation:
|
|
Particle |
Fluid |
Explosion |
Hair |
Rigid body |
Cloth |
Soft body |
|
Attractor |
Yes |
- |
- |
Yes |
Yes |
- |
- |
|
Drag |
Yes |
- |
- |
Yes |
Yes |
- |
- |
|
Eddy |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
- |
|
Fan |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
- |
|
Gravity |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Toric |
Yes |
- |
- |
Yes |
Yes |
- |
- |
|
Turbulence |
Yes |
- |
- |
Yes |
Yes |
- |
- |
|
Vortex |
Yes |
- |
- |
Yes |
Yes |
- |
- |
|
Wind |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
There are several tools to help you view the connections between forces and the simulations that they’re affecting.
Forces in the Explorer
Forces are displayed in the explorer, each one with its own icon. For particle systems, you can expand the ParticlesOp node to see the list of all forces connected per particle cloud.
Forces in the Spreadsheet
You can see which forces are attached to which simulation objects by using the Forces query in the spreadsheet. You can get simulation information for a selected object (or the scene) by running queries in the spreadsheet. This makes it easy to see, for example, which force objects are attached to which particle cloud, and then select those objects or change their values.
To get information using a spreadsheet query
1. Select any force object.
With nothing selected, you can run a query to find all force objects in the scene.
2. In the spreadsheet, choose the Forces query from the Query menu for the selected object.
- To select an element, right-click its name and choose Select Object.
- You can also enter information or toggle options in each cell.
In the schematic view, you can see the links between forces and simulation objects by choosing Show > Operator Links and selecting the force. All forces are represented by a generic force icon (an F with an arrow).
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