RealFlow Dspline tutorial & project overview

We’ve put together a video overview of a 3D animation we worked on for a permanent installation at the Perth Mint in Western Australia.

The project is called The Wonder Of Gold – a 10 minute 3D animated film displayed on a 12 metre x 1.8 metre wrap-around screen in one of the Perth Mint’s new exhibits.

The first part of the video is an overview of one of the sequences in the animation and a look at our workflow. The second part of this video is a tutorial focused on the RealFlow Dspline deamon and how we used it at Reel Pictures, Melbourne to direct our fluid simulation in one of the animated sequences.


RealFlow Dspline Tutorial: text version.

Below, we’ve prepared a text version of our video tutorial above.

Please note: This tutorial is Copyright © Reel Pictures P/L. You are free to link directly to this page, but are not entitled to copy/modify this content without prior written consent. Please contact Reel Pictures if you would like to use this tutorial content in your website or blog.

Part 01 – Introduction & Project overview

Reel Pictures animation studio (Melbourne Australia) has recently used RealFlow extensively in a 10 minute 3D animation for a permanent installation at the Perth Mint in Australia. The project is called ‘the wonder of Gold’ – The animation followed the story of Gold throughout history. The tutorial video focuses on just one of the sequences from the animation. This sequence is from the beginning of the animation, about the origin of Gold. The Incas believed Gold to be the “tears of the sun” the Egyptian “rays of the sun.”

The Animation has been designed for a large 12 m x 1.8 m wraparound screen and is displayed using 5 video projectors.

This tutorial video focuses on how we achieved the magic flowing water effect in RealFlow using the D-spline daemon. We don’t give a step-by-step walk-through of every button we pressed – rather, we want to breakdown the workflow we used. We do cover the D-Spline in-depth however. If after watching the video you would like any further information on anything, do get in touch and let us know!

Part 02 – Basic Overview of the scene – 3ds max

Firstly, we give a look at our scene in 3ds max. Our first step was to layout the camera, objects and animation. we had to accommodate an extremely wide aspect ratio of 20 by 3. It was very important to keep this in mind when trying to layout and plan the scene and it’s animation.

The scene included both the “head and tears” as well as the “Sun + water” animations. We used state sets to switch between the two, changing layer properties, materials, lights and render settings each time. We rendered both sequences out of this .max scene with State Sets/Vray and created the face/sun transition in After Effects.

When approaching the ‘magic’ flowing water simulation, we first made a rough basic spline shape to plan out where we wanted our magic water to ‘flow’. This allowed us to easily visualise the trajectory of the magic water through our ultra-wide camera view. We used the 3DS Max 2D pan and zoom tool to ensure the main body of water would pass through as many key ‘sun ray’ geometries as possible in order to create a real splash!  The spline shape was also extremely important to use as a guide for where to place our D-Spline in realflow. The vertices of the 3ds max spline would become the rough location where we should put the CV points of the D-spline once we were in RealFlow.

With the scene layout, timing and animation set we then sent all these objects to realflow as an SD file using the 3ds Max-Realflow connectivity plugin.

 Part 03 – Basic Overview of scene – Realflow

The next part of our tutorial focuses on our RealFlow scene used for this sequence.  After importing the SD, our first step was to change our global scale. For this sequence, we set the Geometry scale to .1. RealFlow’s default unit is 1 grid square = 1 metre. In 3ds Max, we generally work to 1 grid square = 1 cm. For an accurate scale, we should have set our global scale to .01, but we found that .1 was a geometry scale that worked really well with the fluid and force settings in RealFlow. The scale settings in RealFlow are really important and will obviously strongly dictate the ‘look’ and behavior of the fluid and the forces that are applied to it – such as Gravity. If the scene scale is incorrect, a tiny cup of water will start behaving like a massive lake, for example.

We did a few tests at different scene scales before we settled on .1 and then proceeded to set up our Dspline. The Dspline is extremely powerful, but can be very clunky to control and setup. We cover some tips on how to handle this later in the tutorial. Our dspline is made of 7 CV points and they matched our ‘guide shape’ that we made in 3ds max.

Part 04 – Dspline tutorial

This part of the tutorial is better covered in the video itself. It is at this point that we cover the main settings of the Dspline. The Dspline has 3 main forces that you need to tweak:

  • A vortex that spins particles around the spline
  • An Axial force that will push particles along the spline
  • Radial Strength that will attract the particles towards the centre of the spline

If I hit ‘EDIT’ mode on the D-spline, i can now select individual control points and change those main force settings on an individual basis (for each Control Point). So, as an example: I can have one cv point that is located on a corner with a strong radial strength since it’s right on a bend and I want to keep the particles attracted to the centre of the Dspline. I can give a CP on a straight ‘stretch’ of the Dspline a weak radial strength since the particles will be moving in a single direction and there’s less of a chance they will ‘fall off’ the Dspline. With a weak strength they will break further away from the dspline’s centre axis and the effect of the Vortex will be more obvious.

To explain how all these numbers work:

  1. Control Points (CPs) are the actual force value (for vortex, axial or radial)
  2. The 3 main global values for the Dspline are multipliers of all the values of the CPs.

I will give an example.

  • Just say a single CP of my DSpline has a radial strength of 4.3.
  • The Gobal Radial Strength is set to 2.2
  • The global values above are going to be multipliers of the CP value.

So with the individual CP strength of 4.3 and the global strength of 2.2 So the actual result will be 4.3×2.2 = 9.4

So you can treat these global settings as a way to adjust the power of the D-Spline once your individual CPs are setup. For example, we felt that the entire Dspline was moving particles along the axis a bit too fast, so we changed the axial strength to .85 and this lowered the axial strength of all the CPs.

Check the video tutorial for a few more tips on how to control the Dspline. But in Summary:

You can also change the radius of an individual Control point.

With a larger radius The effect of the vortex and radial strength will no obviously be calculated over a larger space and the particles are able to go further away from the centre axis. But if the axis is not strong enough to counteract this they could fall off the dspline

When moving CPs in Edit mode, there is no Undo feature.

As of RealFlow 2013, Undo does not always track changes to individual CPs. To get around this, Link the CP to another object or helper. There is also difficulty in setting the aim of first and last points on your D-Spline. This is the facing angles of the entry and exit of the DSpline. Depending on which axis you drag the facing angle points, the Dspline may actually move on a different axis, and there is no undo feature.

The best tip when editing the Dspline is to save your scene often and revert to a previous version if things go pear-shaped!

TOP TIP: You can animate all of these settings

Animate all these parameters on a per CV or global basis. If you also link the CPs to other objects that are already animated, you can have unlimited control of what you can produce with this Daemon!

Part 05 – Identifying and fixing Dspline problems

The D-Spline really is a game of give and take – it is a tug of war.
You have to find a nice balance between the Vortex, Axial and Radial strength of your control points to make the fluid behave how you like. If one of these 3 strengths is too strong, things wont look right.

Luckily it is fairly easy to identify what settings need to be adjusted. In the video tutorial, you can see a series of play-blasts we saved as we were building the scene.

In our first attempt, you can see the radial strength is too strong. The fluid is being pulled into the centre of the d-spline too much. You can see which CVs are too strong and which are too weak.

In our second attempt it’s a bit better, but you can see how the axial strength of the DSpline is not high enough, the fluid does not have enough force to travel ‘up’ the d-spline and so it ‘bunches up’ at the bottom, You can see here also how we animated the emitter to try and vary the fluid a bit.

Finally, our 3rd playblast looks a lot better. It is close to the final sim that we used. Here we got things a lot more crazy and developed a balance between the vortex, radial and axial strength. We added a few Cubes into the path of the fluid (offscreen from camera) so it would break the fluid up into 2 streams before it entered frames. The fluid is also torn apart by the many rays extruded from the sun.

It’s actually probably too crazy and we loose a lot of the particles along the way. but due to our final cropping of the scene which is extremely wide, we dont need to worry about the top and bottom.

Part 06 – Conclusion

So that’s an overview of how we approached this scene and a look at the d-spline daemon. We love using Realflow and have learnt a lot from the community and so we wanted to prepare this video to give a little back! We hope this video is also useful to others.

Happy Simulating, and be sure to check out the main Reel Pictures website, facebook page and youtube channel for further tips and tutorials. If you have any questions please post them in the comments section on the video’s youtube page.


Regards –

Alf Kuhlmann, Michael Wentworth-Bell | Reel Pictures P/L