RealFlow 2013

The latest iteration is probably the best off-the-shelf liquid and rigid-body package on the market, says Florian Koebisch.

PRICE: $3,995 / €2,995

OPERATING SYSTEM: Windows / Mac OS X / Linux

FEATURES

  • FLIP & SPH liquid solvers
  • Advanced Caronte rigid-body solver
  • Node-based workflow
  • Alembic support
  • On-the-fly Maxwell Render integration

DEVELOPER: Next Limit Technologies

RealFlow is a well-known off-the-shelf solution for liquids animation. The software from Spanish developers Next Limit has been used in recent movies such as The Avengers and Looper, and hundreds of commercials worldwide. Besides its liquids solver, RealFlow also comes with a fully integrated, stable and accurate rigid-body dynamics system, Caronte.

RealFlow 2013 has some new node-based tricks up its sleeve, too. The old scene management system with its Global and Exclusive Links has been sacrificed for a more modern node-based approach, and a node-based scripting system has been introduced. These script nodes offer valuable tools to technical directors and users who want more control over their simulations. Script nodes take advantage of multi-threading, as well as providing helpful tools such as Signed Distance Fields and processing of information from image files.

The ability to preview simulations using Maxwell offers new workflows to the artists

The ability to preview simulations using Maxwell offers new workflows to the artists

In RealFlow 2013, the Hybrido 2 system for simulating large bodies of water like rivers or oceans has been completely revamped. Now, a FLIP solver (FLuid Implicit Particle, a method originally invented in 1986) is the base for the liquid calculations – basically the same technology that is used in other packages such as Naiad or Houdini. In comparison with the previous Hybrido system in RealFlow, the new FLIP solver feels like a quantum leap – faster, more reliable and allowing much more detailed simulations.

HYBRIDO 2

Hybrido was first introduced in 2010 with RealFlow 5, as a system for simulating medium and large bodies of water. Until then, this had been hard to do with RealFlow, as its standard SPH-based particle solver is more targeted towards splashes or tabletop-scale phenomena. SPH enables you to simulate virtually anything that takes a whole lot of detail, but those highly detailed simulations take their time.

Hybrido offered a simplified method for simulating the base liquid, so SPH was only needed for certain high-detailed areas. This worked fine in many situations, but Hybrido was limited: it was hard to get an acceptable amount of detail out of the base simulations, and one often needed lots of additional layers of SPH on top in order to get the desired quality.

However, Next Limit has addressed the issue by introducing a FLIP solver to Hybrido 2 and renovating the secondary systems for the creation of more detail, foam or other additional elements for simulations. While testing, I was able to simulate a waterfall consisting of more than 200 million particles (base simulation, without additional layers) on an i7-3930K Intel-based workstation with 16GB RAM.

Hybrido 2 integrates extremely well with Caronte RBD. Scene nodes are the new node-based way to work in RealFlow 2013

Hybrido 2 integrates extremely well with Caronte RBD. Scene nodes are the new node-based way to work in RealFlow 2013

The simulation took its time, but the amount of detail was very high; this wouldn’t have been possible with the old Hybrido system. The base simulation alone gives the user quality and detail that wasn’t possible with the old system, even adding tonnes of additional layers of particles on top. A new meshing algorithm has also been introduced, so now one can get the detail of the base simulation into the final mesh.

Hybrido 2 also supports OpenCL GPU acceleration to speed up simulations. Some steps of the FLIP algorithm’s implementation are calculated on the graphics card, resulting in simulations up to 50 per cent faster. Due to the limitations of current graphics hardware, there are still bottlenecks for software like RealFlow: caches of more than 5GB per frame are not uncommon when it gets to real-world quality liquid simulations, so the majority of operations still have to be calculated on the CPU. But cutting simulation time by half is certainly handy.

SCENE NODES

After loading RealFlow, you will see that the old Exclusive and Global Links have gone, replaced by the new node-based interface. At first glance, the new way of working may be confusing – the interface, with its large icons, worked well on a dual-monitor setup but was harder to use on a 15-inch laptop. However, it only took a few scenes for me to realise that the node-based workflow was much more preferable to the previous system: it’s faster and more intuitive.

Hybrido 2 is a new FLIP-based algorithm that allows an amount of detail within sensible simulation times not previously possible in RealFlow

Hybrido 2 is a new FLIP-based algorithm that allows an amount of detail within sensible simulation times not previously possible in RealFlow

Even more important than those new scene nodes – and probably the killer feature in RealFlow 2013 – are script nodes, which allow you to control virtually anything in the scene. There are nodes and tools for vectors, SDFs, Hybrido or SPH elements – for example, you can apply an animated image-based displacement (for example, a wave) that you created in any software. These are very useful tools for more advanced users, but without a basic knowledge of coding they might still be difficult to learn.

However these script nodes are hidden deep down in the user interface, so if you didn’t know they were there you might never discover them on your own – and I’m not sure why the developers would want to bury such a useful feature set. (Under the Simulation Flow menu, right-click on one of the descriptions to open the Node Editor.) Once you’ve found the editor, it’s easy to navigate to and work with, and hopefully Next Limit is planning some interface refinements in the next iteration to make it simpler.

The rigid-body dynamics system Caronte has also been updated, but it’s still not that easy to configure: it’s a typical example of software written by engineers for engineers. Thankfully it’s fun to learn and, as a reward, you will get access to a rigid-body dynamics system that can quickly handle more objects than your standard 3D app, without any jittering.

Caronte has also been speeded up and there are some useful production quality fracturing tools introduced. A cut-down version of Maxwell now comes bundled with RealFlow – not the full package, but you will be able to make a quick render directly out of your RealFlow scene or shoot out rendered previews. This is very useful when trying to evaluate a mesh or particle animation.

Geometry-based fracturing makes Caronte a valuable tool in any artist’s arsenal

Geometry-based fracturing makes Caronte a valuable tool in any artist’s arsenal

RealFlow 2013 is a great product. With features like the FLIP solver, nodes, nodal scripting, new meshers, Caronte and Maxwell, it’s probably the best off-the-shelf liquid and RBD package on the market. With some improvements to the interface, it would be unbeatable.

PROS

  • Fast and reliable FLIP Solver
  • Powerful script nodes
  • Alembic support

CONS

  • No upgrade of Standard Particles/ SPH
  • User interface can be confusing
  • No support yet for viscosity in FLIP

With highly anticipated additions like a FLIP solver and node-based scripting, RealFlow 2013 easily integrates into your pipeline

RATING 4

Florian Koebisch is a freelance FX technical director. He has been an expert RealFlow user for many years, and also offers training and worldwide project consultancy

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