This panel is only visible with a standard particle emitter present in the scene. It governs and controls the interaction between particles and an object.

Collision distance

This parameter describes the distance between the particles and an object's surface in metres. RealFlow automatically adjusts “Collision distance” when an object is added or imported, but after scene scale changes it normally has to be corrected. Good values are around 1% of the object’s largest “Scale” value found under Node Params > Node.

Distance tolerance

By increasing this value, the particles are randomly spread to avoid perfect boundary layers. However these layers cannot be removed completely with this parameter and you should consider a higher emitter "Resolution”, too. Values between 0.0 and 0.95 are valid.

Collision normal

The object's normal directions define inside and outside:

“Both”. Particles can interact with the object's inside and outside.
“Inward”. Particles can only interact with the object's inside.
“Outward”. Particles can only interact with the object's outside.

Collision tolerance

With 0.0 the object is completely watertight. A setting of 0.5 will cause 50% of all particles to go through the object’s surface. 1.0 completely suppresses fluid-object interaction. “Collision tolerance” supports → parameter maps.

Particle friction

A value of 0.0 creates absolutely no friction and a perfectly even surface. Higher values can even stop particles from moving. Settings above 0.9 may cause escaping particles and fluid instabilities. “Particle friction” supports → parameter maps.

Bounce

A value of 0.0 creates perfect elasticity; higher settings make the particles lose appropriate amounts of their energy. The best working range is between 0.1 and 0.8. “Bounce” supports → parameter maps.

Sticky

It can be seen as a “glue factor” to make particles stick on the object’s surface. There are few things you should know:

You can use positive (attraction) and negative (repulsion) settings.
Use a value similar to gravity as a reference and then adjust it further.
This parameter only works with static objects.
“Sticky” supports → parameter maps.

Roughness

This value ranges between 0.0 and 1.0 and adds randomness to the object’s polygon normals to produce a slightly different collision direction. Values, close to 1.0 may cause escaping particles and fluid instabilities. “Roughness” supports → parameter maps.

Temperature

This parameter only affects → gas particles. Higher temperatures make the particles rise, while low settings cause them to sink. “Temperature” is measured in Kelvin: 0 K represent -273° C or -460° F.

Conductivity

This parameter only affects → gas particles. Here you control the transfer of heat between the particles and the object. With 0.0 here is no heat transfer at all.

Thin face test

This parameter is needed when the particles are separated by a thin wall. Here, “Thin face test” must be enabled to avoid interactions between the nearby particles.

Particle force

When the object is an → “Active rigid body” the particles' energy can be transferred to the object making it move. Higher values cause the object to move stronger.

Impulse

This setting works like a repulsion force, similar to a jet or a rocket engine.

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