Daemons - Drag Force

This daemon simulates external air drag forces that slow down faster particles or bodies. A common application would be explosion effects. Without a "Drag Force" daemon the explosion would continue expanding forever, but in real life you can see a very strong and fast acceleration at the beginning of the explosion and a fast falloff after a short time. The "Drag strength" parameter values normally range from 0.0 to 1.0 – however this value is often increased for creating more complex effects, such as melting particles. Values greater than 1.0 will slow down the particles/bodies quickly, even if they are exposed to strong external forces.

The shield effect influences the leading particles of the trail slowing down them down, creating the typical shield deformation. Very high drag strength values can even stop particles or bodies completely. This can cause instabilities in areas where the particles are created. With high values we recommend to use a bounded daemon.

Drag strength

This values typically ranges between 0 and 1, but can also accept higher settings. Settings greater than 1.0 may cause instabilities, and force particles and bodies to stop completely.

Shield effect

When particles move in a close group (for example a stream of water from a hose or a nozzle) the leading particles have a shield-like appearance: the option creates an effect very similar to high air resistance and the particles behave as if they have to push against an invisible obstacle. As a result the leading particles are decelerated. To activate this option it has to be switched to “Yes”. “No” disables the effect. “Yes” also unlocks the “@ shield inverse” function.

@ shield inverse

Instead of slowing down the leading particles, they are accelerated. Groups of particles can be constricted from the main stream, forming groups.

Force limit

With this parameter it is possible to restrict the daemon’s maximum strength. This setting accepts any positive or negative value.

Bounded type

You can choose from three options: “None”, “Square” and “Sphere”. “None” does not restrict the forces to a certain area, while “Square” creates a box. “Sphere” applies a spherical domain around the centre. The size of the bounding volume can be adjusted with the daemon’s scale settings under Node. All three values can be changed independently. “Square” and “Sphere” also unlock the daemon’s ability to create an attenuated force field. The daemon's bounding box can be distorted with the “Shear” parameter under “Node”, but this only affects the visual representation in the viewport. The daemon's scope is not affected.

Attenuation

It is often necessary to create a fall-off to enhance realism, because in nature, forces always show some kind of attenuation – depending on the distance to the force’s origin. You can choose from “Linear”, “Square” and “Cubic”. “Cubic” creates the fastest fall-off.

Affect vertex

This function can only be used with rigid bodies and does not influence particles. If set to “Yes” the daemon affects the vertices of rigid bodies, while “No” only affects the centre of mass.