Objects - Liquid - Hybrido Interaction

Owned by
thomas (Unlicensed)
Last updated: 04 Jun, 2014
5 min read

Objects also have the possibility to interact with grid fluids, but the number of settings is limited. The reason is that grid fluids are used as the core of fluid, while detailed interactions are created with standard emitters. In many cases, objects are used to push the fluid along a certain direction to create breaking waves. For all these applications a large set of parameters is not required.

 

 

Grid friction

This parameter can be mapped: it is possible to load a texture map with different grey scales, representing different zones of friction. You can even use an image sequence for this purpose. To load an image map, right click on the parameter:

Node Params > Grid friction > Right-click > Load texture

A new window is opened, showing various settings for importing the desired images(s). Another method is to enter a global “Grid friction” value, which is constant and valid for the entire object. For a more detailed description of the parameter's mapping feature, please have a look at the subchapter below.

Friction bandwidth

In combination with grid fluids, friction can be described as a field around an object, and this parameter determines its dimension. With higher values it is possible to influence particles which are far away from the surface - according to the given value. If "Friction bandwidth" is set to 0.5, for example, then friction will act on all particles in the area between the object's surface and a distance of 0.5 metres. With 0.0, friction has no influence on the fluid, no matter how high the corresponding "Grid friction" value has been set. The unit is metres [m].

Interaction Factor

Sometimes the interaction between grid fluids and objects might be too weak, so that the object hardly creates any visible turbulence or waves. With this parameter it is now possible to amplify the object's influence on the grid fluid and create more interactions and surrounding waves.

Mapped Parameters

You have already read that many parameters can be represented with image maps – here is some additional information. Image maps create areas of different influence, based on the colours of a bitmap or texture. The adjustments are made from a separate window, providing all relevant parameters and switches to make use of this feature. An additional function is that you are even able to load image sequences for animated parameters. Dark areas indicate zones with low values, while white represents the maximum.

 

 

Especially larger objects can strongly profit from this feature. You can, for example, create a river bed with low “Particle Friction”, while the outside areas have higher values. All this can now be painted to a map and then projected onto your object. This does not only work with RealFlow’s native items, but also with imported objects from SD files. It is important that imported objects carry (correct) UV coordinates.

It is even possible to make the used map or image sequence visible in RealFlow’s viewport. If you cannot see it, or work with multiple maps for different parameters, you can easily to show the desired map with:

Display > Texture > [ Map type ]

If you want to replace the fixed value with an image map, please do the following:

  • Right-click on one of the parameters with a chess board icon.

  • Choose “Load Texture” from the context menu.

  • RealFlow opens a new window called “Load Texture for Parameter”.

  • Fill out the dialogue and confirm your settings with “OK”.

File

Under “File” you can load one or more image files with TGA, BMP, JPG, PNG or TIF format. The path to the image is shown under File. With the “…” button it is possible to open your OS’s file picker. The images must be coloured – either 8 bit, or if supported, also 16 bit. Image sequences are recognized automatically and you do not have to select the first and the last frame. All files with an equal padding are loaded to the canvas.

Channel

Here you can choose one of the picture’s RGB channels. The currently active channel is shown in the canvas and updated according to your selection. “Min. value” and “Max. value” are, by default, the pixels’ intensities. They are spread over the available minimum and maximum range of a parameter but, in case of need, this range can be clipped by entering new values. The shades of the image channel are then spread over the given settings.

Min. value/Max. value

The grey shades of the loaded image will be transferred into values ranging from “Min. value” to “Max value”. So, the lowest grey tone will get the value from “Min. value”, and the highest grey tone receives the value from “Max. value”. All the other grey scales are calculated automatically between the given minimum and maximum.

Please bear in mind that the maximum value is 1.0 and “Min. value” cannot be greater than “Max. value”. This feature is also very interesting if you see problems like local instabilities or exploding particles. This can often be observed with very high “Particle friction” settings. In such a case, simply decrease “Max. value”, e.g. to values around 0.1.

Min. frame / Max. frame

These values are important for image sequences. You are able to specify a certain frame range that is used for parameter mapping. Simply enter the desired start and/or stop value and the frames outside of this range will be ignored.

FPS Ratio

With a value of 1 the image sequence is played at its original speed, e.g. 30 FPS. If you want to achieve faster or slower playback then you have to change "FPS Ratio" accordingly. Values above 1 will increase playback speed; smaller values are used to slow it down.

Offset

If you do not want to start with the first frame of your sequence, you can determine an “Offset” from which the series will start playing.

Loop

This option creates an infinite back and forth loop from the currently loaded image series.

Control buttons

They work exactly as in other video players. You can go to the first or last frame, to the previous or following frame, and start/stop playback. The slider allows you to scrub through the entire sequence and jump to a certain frame.

Skip

Finally, the “Skip” option is related to “FPS ratio”: while playing back an animated sequence, RealFlow cannot always achieve the given FPS rate. By checking “Skip”, RealFlow will play the image sequence with the adjusted FPS rate, but some images might be dropped. Without “Skip”, RealFlow shows all images, but there is no guarantee that the desired frame rate can be maintained.