By Hammer Chen

Have you ever wondered how to create a bullet-time effect for liquids with Phoenix FD? Especially when working with rigid body simulation? The answer is surprisingly simple: animate the Phoenix FD's "Time Scale" parameter. In this article, I am going to show you the workflow.

1. Scene Setup
We have two wine glasses in the scene  and a sphere flying from right to left, that hits and breaks the glasses. You can use any package to simulate the rigid body dynamics, for example,  PFlow mParticles or RayFire. In this case, I use thinkingParticles.

2. Sim the RigidBody with constant speed
Before we start the fluid simulation, we have to simulate the rigid body first. See the constant speed video example, where there is no change of speed through out the animation. Note, that I do slow down the overall simulation for aesthetic reasons (around 70% of real-life speed), but overall it is the same rate.

3. Bullet-time the rigid body simulation
Next, based on the previous setup, we add a bullet-time effect for rigid-body simulation. The various speed of the overall animation can be easily done by using the “Freeze Operator” in thinkingParticles. In case you're not using thinkingParticles; with Rayfire - you can baking the rigidbody animation and then retiming by using 3dsMax's "Retime Tool".

By increasing the value of the Freezing% parameter, the rigid body will slow down, and eventually fully stop when it reaches a value of 100%. So, we animate this value to change the dynamics speed as desired.
4. Align Phoenix FD's Time Scale to Rigidbody
Because Phoenix FD allows us to animate the “Time Scale” parameter directly, so all we have to do now is to align the “Time Scale” to the “Freezing% parameter temporally.
Note how the “Time Scale” values’ curve is kind of a reversed Freezing% one. For example, in frame 61, Freezing% is 30% and Time Scale is set to 0.7.

6. Liquid Simulation
Now, thanks to the artist friendly design of Phoenix FD, we press the Start button and simulate the liquid motion. The results will be just what we want - animated liquid with bullet-time effect that perfectly aligns with the rigid body animation temporally. The fluid can collide with the rigid body in the right place and at the right time. No post-simulation re-timing is required, no flickering artifact is present because of the post-simulation retiming. Enjoy~

By Hammer Chen

In this article, I am going to share some tips & tricks of how I made this deer crossing river animation. Although it might look daunting at first glance, the settings for Phoenix are quite simple. The most critical thing for making this animation is the hardware.


As you can see, the total cache size for the whole animation (250 frames) is around 535 GB. So you better have a faster RAM and a hard drive with enough space for this kind of project. Once you have your hardware ready, leave it to Phoenix, Don't worry, Phoenix FD does support large-scale fluids like this one.

The image above shows my scene setup. The herd of deer is generated from a single rigged deer, duplicated by using thinkingParticles. There is no animation variation of the deer character, so the setting is simple, only offsetting animation for each deer.


Phoenix FD Liquid Simulation grid: Note that I keep my simulation grid very narrow, just wide enough to cover the region where the deer are crossing the river. Remember, the smaller the grid - the faster the simulation. For other parts of the river, we will use 'Ocean Mode' in combination with displacement and no simulation will be involved.

Phoenix FD will extend the liquid mesh from the camera frustrum, so you will see deer crossing river as if the river is infinitely large from camera view. Everything I do here is to make sure simulation is highly optimized and can be simulated efficiently.





After you tick the Foam option of your Phoenix FD Liquid Simulator, Phoenix will automatically create a Particle Shader in the scene. In this helper object, we can set the color, size, even multiply the number of the foam. Since this is a muddy river, we set our foam color to light brown color.



We are all set. Now just hit Start and simulate. It will take a few hours, depending on your machine. Here is the final animation:

By Hammer Chen

In this article, I am going to share my tips & tricks for making realistic honey with Phoenix FD.

1. Modeling a honeycomb
Finding a photo-realistic model is very difficult. Even you have a budget to purchase from the online shop doesn't guaranty you get the right 3D model for the project. So I decided to model it by myself.

I found a handy tool from Scriptspot - Honeycomb, a maxscript by Anubis. This script allows you to generate a honeycomb shape with just one button.

After some extrusion, boolean cut, I got this rigid, artificial looking honeycomb. I will use this as a base and transform it into an "organic" model.

The model above was sculpted digitally with Autodesk Mudbox. Now my honeycomb model is ready!

2. Liquid simulation RnD
Because the 3D model of honeycomb is cumbersome, so it's better to work with simple primitive first. Once we got the right settings for simulation, we can use the high-resolution 3D model.

Here I used a simple plane as the liquid source (size around 127 X 26 cm). Beware that Phoenix FD doesn't like geometry without thickness, if you're having trouble emitting liquid from a simple plane, adding a shell modifier to it should fix the issue. In this case, no thickness is fine. The key is to put a Stucco texture as LiquidSrc's mask.


Those are settings for the Grid and Dynamics. Noted the Viscosity and Surface Tension play important rules when simulating realistic viscous liquid like honey. Once we are happy with the results, let's move on to the next stage.

3. Simulation for production

First of all, I manually selected part of the honeycomb - top portion and bottom, clone and detach them. In the image above, I moved the two meshes aside for illustration purpose (so you can see them better). Make sure the two meshes are not solid object so they won't collide with liquid.

Since we already got the excellent settings for dynamics in step 2. Assign the two meshes (top and bottom) as our liquid sources. Then hit the Start button of the Phoenix Liquid Simulator, and you should have similar results above. Please noted the 3D honeycomb is 150 X 150 cm, roughly ten times than a real-life honeycomb. Use a little larger geometry can be more comfortable with adjusting a simulation.

To make the animation more interesting, I animated the Time Scale and set it from 0.5 to 0.1. So you will have honey slowing down during the whole animation. Simulate again to see the results.

4. Lighting
Nothing fancy for the lighting. I created one V-Ray Dome Light - HDR plus one VRay - Plane light in the scene.

5. Honey material
Here are my settings for material for honey, using VRay standard material. Making realistic honey is very difficult. Play around with "Fog multiplier" , "Fog bias" and "Light multiplier" to match your scene.


6. Final rendering

Hope you like this article and find it useful~

By Hammer Chen

Whitewater is formed in a rapid, when a river's gradient increases enough to generate so much turbulence that air is entrained into the water body, that is, it forms a bubbly or aerated and unstable current; the frothy water appears white. --- Wikipedia

In this article, I am going to show you how to set up whitewater shading with Phoenix FD.

To set up a scene for whitewater shading you will need:

1. A Phoenix FD Liquid Simulator - for simulation of liquid and generate "Vorticity smooth" data
2. A Phoenix FD Fire/Smoke Simulator - this is not for simulation. This Fire/Smoke Simulator doesn't have to be high resolution, because it purely functions as a container to load up "Vorticity smooth" data from Liquid Simulator, and shading / rendering them as smoke.
3. LiquidSrc

Key steps:
1. Create a Liquid Simulator in the scene, just as regular liquid simulation setup, except you need to export Special Grid Channels called "Vorticity Smooth," this data will serve as a source of the whitewater. Run simulation.

2. Create a Fire / Smoke Simulator in the scene, be sure to align it with a liquid simulator. The two simulators don't have to be the same size or same resolution, but their default pivot position has to be perfectly aligned.

3. In the Input rollout of the Fire / Smoke Simulator, change the path from default to "$(same_as_output) PhoenixFDLiquid001". This specifies the source of "Vorticity Smooth" data that generate from step 1.

4. In the Rendering rollout of Fire / Smoke Simulator, check the Cutter Geom option, and select the PhoenixFDLiquid as you created in step 1. Click on Volumetric Options...

5. In the Volumetric Options of the Fire / Smoke Simulator, change the color of Constant Color to white color or any other color you like for "whitewater." In this case, I gave it a light blue color. Set the Simple Smoke Opacity to a higher value so you will have a more pronounced whitewater shading.

by Hammer Chen

For most of Phoenix FD users, you probably aware there is a helper called PathFollow comes from Phoenix FD. It allows your fluid (water or smoke/fire) moving along a spline. But if you leave its parameters as default, there are high chances you get this cucumber shape of water stream:


The key to making your water stream looks realistic is introduce falloff to the FollowPath. To do so, you can also use Phoenix FD 's Force Preview while tweaking the force:

Noted the color difference at the edge of the spline, you see a beautiful red-to-blue transition of that force strength.


To give you more idea, one the left the influence is set to 1.0; one the right influence is set to 0.25

Another critical factor is noise. Put a Phoenix FD Turbulence force in your scene can make a huge difference.

This is my settings for the PHXTurbulence:

Settings for Dynamics:


And an overall setup for the scene:


Enjoy and have fun!