Applying forces

You can direct particle motion with forces. Forces can emanate from geometry in the scene (for example, you can create a sphere and have it attract or repel particles), or you can create a general directional force (such as gravity).

How to direct particle motion with forces ¶

To...	Do this
Make geometry attract or repel particles	Click the Point Attract or Curve Attract button from the Particles tab of the shelf. Select the particle system you want to be attracted or repelled and press `Enter` to confirm your selection. Select the object or curve you want the particles to be attracted to or repelled from and press `Enter` to confirm your selection. The degree of attraction/repulsion can be modified with the Force Scale parameter on the Force tab of the POP Attractor DOP node. A positive value will attract the particles and a negative value will repel the particles.
Create a general directional force	Click the Force Particles tool on the Particles tab of the shelf. Select the particle system you want to be affected and press `Enter` to confirm your selection. Set the Force parameter on the POP Force DOP node to affect the particles. By default this is set to `-9.81` in the Y direction, to apply a gravity force. Note You can also use the Fan Particles or Wind on Particles shelf tools, depending on how you want the particles to react to the directional force.
Add random force to particles	Click the Force Particles tool on the Particles tab of the shelf. Select the particle system you want to be affected and press `Enter` to confirm your selection. Modify the parameters on the Noise tab of the POP Force DOP node. You can change the Swirl Size, Pulse Length, Roughness, Turbulence, etc,
Move particles along, toward, or around a curve	Create a curve using the Draw Curve shelf tool. To get a smooth curve, use the tool’s Bezier mode. Create a particle system along the curve using the Location shelf tool. In the viewport, place the cursor over one end of the curve and press `Enter` to define the system’s origin. Click the Curve Force tool on the Particles tab. Select the curve you want to affect your particles and press `Enter`. On obj level, double click the `AutoDopNetwork` node to dive into it. Adjust the POP Curve Force DOP’s parameters and forces to tame the particles. Turn off the Gravity Force DOP node with the Bypass switch or delete it.
Make particles flock together	Create a particle system using the Location or Source shelf tools. Click the Flock Particles tool on the Particles tab. On obj level, double click the `AutoDopNetwork` to dive into it. Open the POP Location or POP Source DOP’s Birth tab. For Const. Activation, enter `$F<=5` to limit the creation of new particles to five frames. Increase Const. Birth Rate to get a dense particle cloud. Flocking particles often have very large dimensions. In the viewport, use the to zoom out. Select the the POP Flock DOP. You can choose the Number of Centers to determine how many different clusters of particles are formed. Set Avoid Force to `3` to give the particles more space. Set Avoid Max Dist to `0.5`. This is the distance where particles start to avoid each other. Note To move the flocks, you can use a POP Attract DOP node to have them follow an object (such as a character), or use other POP Forces DOP to direct them. Tip To make the particles stay together and create a denser particle cloud, add a POP Drag DOP after the POP Location DOP. Change the Air Resistance parameter to control the particles' speed.