SPH - Object

Though RealFlow offers a wide variety of different emitters, they are sometimes not flexible enough and it is necessary to transform some custom geometry into an emitter. The outside polygons (faces) of the object will be used to create the particles. Normals play an important role here, because they determine the direction of emission. By default, the normals point outward, but it is also possible to flip them and fill an object gradually. Please note that some particles might penetrate the surface in spite of adequate settings.

You can declare any item as an object emitter, regardless of whether it is native or imported. The only premise is that it has to be triangulated, but that is valid for any geometry inside RealFlow. For even more flexibility it is possible to select certain polygons or vertices for emission.

Object

To make an item creating particles it has to be defined as an emitter, of course. This function opens a node picker to select any available object from a list. Please note that you can only choose one object at a time and multiple selections are not allowed.

Parent velocity

An object, meant to emit particles, does not necessarily have to be a steady object it can also be animated or obey the rules of rigid body dynamics. If the emitter object is moving, RealFlow takes a certain amount of its velocity and transfers it to the particles during the state of creation.

Distance threshold

Here you can determine how far away the particles should be from the object’s faces during birth. This produces a visible gap between the particles and the object’s surface. The dimension of this value is measured in metres [m].

Jittering

The arrangement of an object’s polygons always leads to unwanted patterns in the fluid. To avoid this, “Jittering” can be used. It ranges between 0 and 1 and adds randomness to the creation process.

Speed

This value defines the speed of the particles at the time of creation. The checkerboard indicates that you can use a bitmap or an animated images sequence with this emitter. White pixels will be interpreted as particle emitted areas, black pixels will not generate particles. To use a texture with this parameter, right-click on the value and choose “Load texture” from the context menu. A new window will open with settings and parameters for loading and adjusting the speed map. If you want to use the numerical value again, choose “Unload texture”. When you have a texture loaded, the numerical value will be totally ignored. "Speed" is measured in metres per second [m/s].

Randomness

You can randomly vary the speed of the particles to avoid regular patterns. “Randomness” accepts any positive value, but as always you should avoid extremely exaggerated values in RealFlow. With very high values the particles might explode.

Smooth normals

This function makes the particles follow the smoothed normals of the object’s surface and your should use it when the emission appears to random or fuzzy.

Select Faces

As mentioned initially, you have the possibility to select particular polygons from the object and there are two ways to do this: The first method is to click on the desired face. Multiple selections are supported by pressing the Shift key. You can deselect faces by clicking on them with the pressed Ctrl/Cmd key. Please note that “Select Faces” does not recognize hidden polygons by default. Everything what is under the mouse pointer will be selected, but you can activate a function to limit a selection to polygons visible to the user:

Edit menu > Back culled selection

Another way is to hold the left mouse button and drag the mouse over the desired area. This will create a rectangular selection, including faces hidden to the viewer. Once you are satisfied with your selection, deactivate “Select Faces” to confirm your choice. When the object's polygons are very small you have to increase the emitter's "Resolution" value to trigger the emission of particles.

Select Vertex

This button works exactly like the “Select Faces” feature, but is limited to the source object's points.

Clear Selection

You can clear the entire polygon and/or vertex selection with a single click on this button.