Experienced users will recognize many settings from RealFlow’s standard emitters, but there is also something new to explore.

Visible

This setting is used to make the selected domain invisible or visible. It is sometimes necessary to look behind or inside a fluid’s particle cloud to evaluate the movement of rigid bodies or other particles, for example.

Domain

With grid fluid domains you can select from four different modes to determine how the domain’s box should be displayed:

None	The box representation of the domain is hidden.
Box	This is the default setting. With this mode you can see the domain around the fluid.
Cells	All the cells of the domain are shown. With particles this mode can be a little confusing due to the large number of cells.
Back cells	The grid elements are projected on the domain’s walls like a 2D raster.

Please bear in mind that there is a difference between the domain box and the so-called projection plane:

The plane is the “HY_Domain” node's viewport representation and shows how textures (displacement, velocity, vorticity) are projected on the fluid's surface. The small cubes represent the adjusted “Cell size” value. The plane’s height position, on the other hand, can be used in combination with the Hybrido mesh's “Open boundary” option: all polygons below the plane and outside its boundaries will be clipped.
The domain is only visible during simulation around the fluid and represented as a box. All options, given here, only affect this box, but not the projection plane. Another difference is that the projection plane can be moved freely in the viewport, but its position does not influence the position of the domain's simulation box.

Detail

Here you can choose from 5 different modes (“Draft” to “Best”) to adjust the representation of the domain’s particles in the viewport.

Display type

You can choose whether you want to display the particles as points or shaded spheres. The second type, of course, needs longer to be drawn, but gives you a better idea of the fluid's body.

When you use the “Sphere” option with Hybrido's grid fluid domain, the particle are displayed as spheres..

“Arrow” is the last option and here the particles are displayed as arrows indicating a particle’s property vector, e.g. “Velocity”. The direction of the arrowhead shows the direction the particle is moving, while its length illustrates the magnitude or “speed value”. Arrows are also dyed to represent a parameter’s differences. For this, “Min range color” and “Max range color” are applied. "Arrow" and "Sphere" can only be used when the “Use Shaders” option is activated under:

Preferences > Display

Size

Each particle is represented by a dot or a sphere and with "Size" you can adjust the size of the viewport representation.

Particle %

Hybrido simulations often consist of several million of particles and viewport navigation can become very slow. If you do not want to display the entire amount of particles, you can enter a percentage value here: with 100% all particles are displayed, with 25% only one quarter etc.

Property

This mode is used to show different physical characteristics of the fluid. With Hybrido domains you can choose from a wide variety of attributes.

If you want to use “Splash/Foam emission”, please also read the chapter “Splash Preview Workflow” directly below.

Velocity	Shows the velocity for all three directions in space X, Y and Z.
Velocity.[a]	Displays only the X, Y or Z part (= [a]) of the current velocity.
Vorticity	To visualize the particles' spin, activate this mode.
Normal	Each particle carries a normal vector that can be made visible with this option.
Constant	Used to apply one colour for all particles without shades or gradients.
Splash/Foam emission	With this powerful mode it is possible to preview the areas where splash and foam particles will be emitted. These areas, where splashes will be created, are displayed in white, while the non-emitting particles are dyed with the colour from “Min range color”. This option unlocks a couple of additional parameters. ^*)

^*) The associated parameters (@ curvature threshold etc.) are only accessible with this mode.

RealFlow will not create any particles during the preview: you will only see the areas where particles are generated when you simulate the splash pass with the threshold values you have adjusted in the parameters below. If you want to learn more about the threshold values, please visit the “Splash Emitter” page.

@ curvature threshold

Curvature can also be seen as the surface's “roundness”. With this parameter you can control the amount of “roundness” that is required to emit splash particles. Smaller values are used to emit more splashes. This parameter is dimensionless and any value greater than or equal to 0 can be used.

@ angle threshold

This parameter takes the fluid surface's main direction of motion into account. The particles themselves also have an individual direction of motion caused by their velocity. Hybrido measures the angle between these two directions, and when the angle is between 0° and the given threshold splash particles will be added. The value is measured in degrees [deg].

@ speed threshold

When a particle's velocity is greater than the given threshold value it will be able to emit splashes. This parameter is dimensionless and does not have an upper limit.

@ vorticity threshold

Here you can adjust a particle's amount of vorticity that is at least required to emit secondary particles. This parameter is dimensionless and does not have an upper limit.

@ neighbors threshold

A particle can only emit secondary particles if its number of neighbour particles is equal or greater than the adjusted value. This parameter is dimensionless and does not have an upper limit.

Automatic range

This option automatically calculates the colour gradient for the selected property. The colours that are used for this purpose can be selected from the “Min range” and “Max range” colour fields. If you want to define a custom range instead, simply switch this option to “No” and enter appropriate values under “Min range” and “Max range”.

Min range/Max range

When “Automatic range” is turned off, you have to specify these minimum and maximum values for displaying the colour gradient. The minimum values will then be represented by “Min range color”, the maximum values are shown with “Max range color”. To find out minimum and maximum velocities, for example, open the Statistics panel for “V min” and “V max”. The parameters' dimensions depend on the chosen "Property".

Min range color/Max range color

Clicking on these fields opens a system colour browser to choose any RGB value from a given palette. These colours can be used to create certain impressions, such as fire or smoke.

Max range clamp color

When you work with custom ranges it often happens that values are clipped. An example:

The maximum velocity magnitude in your simulation is 17.53667, but under “Max range” you have entered a value of 10.00. In this case, RealFlow will display all particles faster 10.00 with the colour specified here – by default this is white.

Splash Preview Workflow

With the Hybrido domain's “Display” panel it is possible to preview the areas where splash particles will be created. For this purpose, you will find a couple of threshold values. These parameters are exactly the same as you can find under the “Splash” emitter's “Splash Creation” tab, but they will not create any particles. Their only function is to make the splash emitting particles visible. To activate this feature, please choose:

Grid fluid domain node > Node Params > Display > Property > Splash/Foam preview

Once you have enabled the preview function, it is possible that the fluid particles will show a uniform colour. In this case please go the next or previous frame. After a few seconds (this depends on the number of particles), the fluid's viewport representation should be similar to the image below:

Now you can start adjusting the associated threshold parameters to see and evaluate the splash or foam emitting areas. Please bear in mind that “Splash/Foam preview” does not create or remove any particles. Its only purpose is to visualize where splashes or foam will finally occur. The preview will be updated automatically every time you change one of the threshold parameters. We recommend you use this feature only after the core fluid pass has been completed. It is not necessary to apply the preview during a running simulation. Once you have found a satisfying solution, you should note the values or tale a screenshot. Then, they can be transferred to the appropriate parameters of the splash and foam emitter(s).

If you want to use the determined values with foam emitter(s) it is necessary to enable the following option, because otherwise the emitter's threshold values cannot be accessed:

HY_Foam > Node Params > Foam Creation > From domain > Yes

Please note that it is not possible to show both properties (splash and foam) simultaneously, for example with different colours. When you make your settings, you will always do this for either splashes or foam. If you want to get previews for both elements you have to do this with two passes: in one pass you adjust the parameters for the splashes, the second pass is for the foam particles.

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