Create a new CINEMA 4D scene, setting the Frame Rate to 60FPS and the Document Time to 150F. Add a Circle spline to the scene and leave the Plane at XY. Check the Ring and Ellipse options and set the Radius, Radius Y and Inner Radius to 500cm, 265cm and 430cm respectively. Add this to an Extrude NURBS and extrude it by 100cm before making it editable. This elliptical ring is our main piece of geometry that will drive our fluids in RealFlow. Now add four cubes with the dimensions of 312 x 1,250 x 1,000cm and arrange them along the X-axis so that there’s no space between them. These cubes will serve as our fluid containers. Before we’re ready to export our scene we’ll need to make a simple animation of the ring. Add the ring to a Null, then animate the position and rotation for both the ring and the Null so that it moves through the cubes. The splash we’ll create in RealFlow is a direct result of the geometry and motion of the ring, so experiment with different shapes and animations to get a range of various results. We’re now ready to export the scene with the RealFlow Exchange plug-in. Add all the elements, set the Frame Range and the location for the SD file and hit Export.
Head into RealFlow, import the scene file that we just created, then insert four Container and four Fill Object emitters, one for each colour. We also need four Filter Daemons, a Drag and a k_Volume Deamon. Navigate to your Simulation settings, change the FPS to 30 and the MAX substeps to 50-75. You should also adjust your Scale values if necessary. To keep track of all your various scene elements, rename your emitters and Daemons according to their colour. You can also organise them into groups and layers.
We are now ready to adjust the Particle attributes of our emitters, so lower the Resolution to 0.5. We’re trying to get the look of thick paint, so set the Density to 1,200 and the Internal Pressure to 0.1. The External Pressure for the Fill Object emitters can be left at the default of 1, but raised to 20-30 for the Container emitters to help the splash keep its shape. Enter 8-10 for Viscosity and 0 for Surface Tension. Experiment with these settings to achieve different results. Set the Strength of your Drag Force Daemon to 1-1.5, then enter the Fill and corresponding Container emitters into the Source and Target fields of the Filter Daemons. Set the Attribute to Speed and the Value to 2. We’ll need to work with exclusive links to control the particle interaction, so clear the Global Links panel and drag all your emitters to the Exclusive Links panel. First add the Drag and k_Volume Daemons, as well as the ring, to all the emitters, then add the Filter Daemons to their corresponding Fill Object emitters. Add the Container Only attribute to the Container emitters and the Fill Only to the Fill Object emitters. Fill the cubes with particles and run a test simulation. To be able to see what’s going on, turn off the Visibility of the cubes and the Fill Object emitters.
Now that we have a first impression of the simulation, all that’s left to do is raise the Resolution. Here we’ve used a value of 3 for the final simulation, but depending on your hardware and your available time you can easily go higher. Adjust the Strength of the Drag Force Daemon, set the MIN to 50, MAX substeps to 150 and hit Simulate.
Add a standard Particle Mesh to your scene and insert the four Container emitters. Leave the Type at Metaballs, enter a Polygon Size of 0.0225, turn on Filtering, set both Relaxation and Tension to 0.1 and change Steps to 96. Leave the Blend factor at 95 and enter 0.0175 for the Radius. Make sure the Polygon Size always stays above the Radius to avoid broken meshes and also activate Deformation. Building the mesh usually involves a lot of trial and error. All the settings are interdependent, so here it’s best to make a few tests and compare results.
Head to CINEMA 4D, add a RealFlow Mesh Importer and enter the file path in the Setup panel to load the mesh. You will notice that the mesh has four Weight tags, which we’ll use to mix the fluids. Create a new material and check the Alpha box. Add a Vertex map effect to your Alpha, then just drag the first Weight tag into the Vertex Map field. Change the colour of the material and add some Fresnel reflections according to your taste. Do the same for the rest of the remaining colours to finish, then stack the four materials onto the mesh.