RealFlow Wisdom

RealFlow blog: Tips, Technics and Scripting.

Mixing fluids by Graphs and RenderKit

This time I bring a new method to mix fluids with using Graphs in RealFlow.

Thanks to the help of Alex Ribao from Next Limit I would like to share this graph to mix two fluids using the temperature channel of the fluids. This idea is not mine I took it from Thomas Schlick, but instead of using py script we use Graphs that is faster in calculations in some cases.


Capture from Realflow2015 (beta)

This a pretty simple scene of two fluids, yo can set different properties, as viscosity, density, etc. Even using this method I think you could do it more complex and mix properties between fluids.

But firstly I would like to prevent you that exist some tricky things in this method that we have been aware. By default liquid emitters have not temperature channel so to create them we have to switch them to Gas  and we should set the temperature to 0 for one and to 1 for the other and switch again to Liquid, so we had the channels created.

Once done this we only need to load the Graph to the stepPre slot in the Simulation Graph.


The graph is quite simple, the particles from both emitters are loaded and read positions and temperatures, then through creating a distance field the particles transfer the temperatures between them and these are updated. The mixed area can be controlled with the CellSize node, although you can add extra control in the rendering process too. For rendering, this time I used Arnold through RenderKit, now I am testing the workflow with Maxwell and will try in VRay too. This are the connections for Arnold.


June 3, 2015 Posted by | Uncategorized | , , | Leave a comment

Silly tips!! – Part I

Here you go some newbie tips I had in the treasure trove, remember them is never a bad idea.

Relaxing fluids:

If you need to a pool of fluid you always need to relax the fluid to get a initial state, you can simulate during a lot of frames.

To accelerate this process you can use a KSpeed daemon activating the  limit&keep option, I use to animate the Simulation attribute in the first frame….


… and activate the Lock function in the time line, depending on the scene set up it´ll be needed increase or decrease the number of frames for the countdown.


Breaking patterns:

Usually emitters in RealFlow  have a pattern in the emission, the slices. To avoid them you could use several methods:

  • Use the H/V random
  • Adding some randomness in the emission, you could do this with a simple expression in the speed attribute 4.5+rnd(1), 4.5 is the main speed.
  • You can use a Noise daemon linked to the emitter and bounded to the space icon.


  • Using droppers, a dropper is a basic geometry to make the fluid collide before to drop down, you can make it simple with planes or modelling it in a 3d platform so you could get nice and realistic patterns.

Simulation in vacuum:

Remember RealFlow is not in essence a Computational Fluid Dynamics software (CFD) and works always in vacuum, so if you would need to simulate with accuracy  you will need to add a second fluid -air- interacting with the main fluid, but this could be against the simulation times.

Sticky Attribute:

It is really important the normals aim to the collision side in order to get correct results, the sticky attribute is a force applied to the colliding particle and is inverse to the geometry normal.

March 20, 2013 Posted by | Tips | , , | Leave a comment

Crowd Flow: old tests

Looking in my old stuff I found some comparative videos I would like to share, these are not really relevant but could help anybody to have a better understanding of this tool.

Sorry! In some videos attribute values  are not  showed.


Aproach Slope

Aproach Speed

Aproach Strength

Outer Boundary

Cover Speed

Cover Scape Limit

Cover Outer Limit

Cover Inner Limit

November 5, 2012 Posted by | Daemons, Particle Base Fluids | , , , | Leave a comment