Ship in the Ocean

This tutorial is created using Phoenix 4.41 Official Release and V-Ray 5, Update 2.1 Official Release for Maya 2018. You can download official Phoenix and V-Ray from https://download.chaos.com. If you notice a major difference between the results shown here and the behavior of your setup, please reach us using the Support Form.

The instructions on this page guide you through the process of creating a simulation of a ship sailing through the ocean using Phoenix and Maya.

The process of correctly setting up the scale of the objects used in the simulation is covered in detail. Many workflow suggestions and example videos of commonly used simulation parameters are included as well.

The main takeaway from this tutorial is an intuitive understanding of how the Foam and Splash parameters work together to produce foam from the collision of the vessel with the liquid surface.

Download Project Files

Scale is crucial for the behavior of any simulation. The real-world size of the Simulator in units is important for the simulation dynamics. Large-scale simulations appear to move more slowly, while mid-to-small scale simulations have lots of vigorous movement. When you create your Simulator, you must check the Grid rollout where the real-world extents of the Simulator are shown. If the size of the Simulator in the scene cannot be changed, you can cheat the solver into working as if the scale is larger or smaller by changing the Scene Scale option in the Grid rollout.

Go to Windows → Settings and Preferences → Preferences → Settings and set the Working Units to Meters. As the focus of this tutorial is a large-scale ship simulation, setting the units to Meters seems like a reasonable choice.

Set the Time to 29.97 fps. We do this to ensure the setup is identical to the Ship in the Ocean tutorial for 3ds Max. You may skip this step if you find it unnecessary. Keep in mind the final result of your simulation may turn out slightly different.

If you open one of the provided scene files - Phoenix_ShipInTheOcean_Maya2018_Start.ma, you will find an animated camera and the ship geometry.

In this example, the ship is already set up to be of proper, real-world size.

However, that may not be the case with your ship or boat so let's see how to go about fixing this.

1. Try to find some information regarding the real world size of your model. The object in this scene is a replica of a typical Navy warship. Wikipedia tells us that the length of the ship is 154 meters. If your model is fictional or you can't find any info, use the measurements of an object that somewhat resembles yours.
2. Create a Poly Cube around your object with the Width / Height / Depth set up as a reference. In this example, the Length (Depth) of the ship should be 155 meters, its Beam (Width) 20 meters, and it should 'sink' (Draft) 9.2 meters into the water.
3. If your model doesn't fit into the specified measures, use the Scale tool to uniformly scale it up/down until it is of the correct size.

That is all. Please don't delete the measurement box for the time being - you are going to need it when setting the Phoenix Liquid Simulator Initial Fill Up level.

The ship in this example is already animated for you. The speed of your model will heavily affect the entire simulation. It is crucial that you are mindful of the speed of your ship as it travels through the liquid.

Here is how to approach the animation methodically.

1. Either use the Internet to find how fast the real-world version of your model is/or if fictional, consider using something with similar properties as a starting point (i.e. if you're simulating a Medieval warship, find out how fast a typical Navy warship from that era was). The speed of this vessel is 56 km/hour, according to Wikipedia. That's 56 000 meters / 3600 seconds, or 15.56 meters per second.
2. The Frame Rate in this example is set to 30 frames per second. Therefore, 15.56 meters / 1 second is 15.56 meters / 30 frames = ~0.5 meters per frame.
3. Recall that the Units are set to meters, therefore 1 unit is 1 meter. That means our ship should travel about 1 unit for every 2 frames.
4. Determine the length of your simulation. In this example, the length is 1000 frames. Therefore, our ship should travel ~500 units over those 1000 frames.
5. Create the animation. In this example, the keyframes are as follows: [Frame 0 Translate Z (0m)]; [Frame 1000 Translate Z (-400m)].
6. Open the Windows → Animation Editors → Graph Editor and set the tangents for the animation to Linear. It would look strange if the ship was speeding up at the start and slowing down at the end of the animation, which is the default behavior of the Ease-In - Ease Out tangents setup by Maya.

That is all. Play the animation to make sure everything is working correctly.

Go to Frame 0 so the ship is centered at the origin.

Create a Phoenix Simulator and position it such that the front of the ship is close to the -Z wall of the Simulator. Be sure to leave some extra space at the back of the ship - that way, the foam generated by the ship as it travels through the water will spend enough time inside the Simulator to form interesting patterns.

Speaking of foam, Phoenix provides another feature to boost performance - Foam particles can live outside the bounds of the simulation box. What this means is that you can have a very long trail of Foam particles generated by a relatively small Simulator.

Here are the exact dimensions and position of the Phoenix Liquid Simulator at Frame 0 (so the ship is centered at the origin):

Translate: [X: 0] [Y: 4] [Z: 40];

Grid Size: [X: 205] [Y : 20] [Z: 512];

Cell Size: 0.5m;

Scene Scale: 1.0.

Optionally, you can rename the PhoenixFDLiquid001 to phx_simulator_01 to keep your scene organized.

Set the Simulation Template to Liquid from the drop-down at the top of the Phoenix Simulator parameters in the Attribute Editor.

By default, the Phoenix Simulator is set up for Fire/Smoke simulations. When the Liquid preset is selected, the FLIP solver is enabled instead (to manually do this, go to Liquid → Enabled) and the Rendering → Render Mode is set to Mesh. The Fuel rollout and some parameters not utilized by the FLIP solver also become invisible.

Go to Frame 0 and place the Simulator inside the animated group holding the ship geometry.

To test if this has been successful, scrub the Timeline. The Simulator box should now follow the animation of the ship.

Unhide the box used to measure the ship size. Recall that the Draft (the sink level) is 9.2 meters. The Draft is measured from the lowest point of the ship so if you were to position the box such that its bottom face is aligned with the bottom of the ship, its top face will give you the Draft.

Then, open the Liquid rollout and enable Initial Fill Up.

Hit the Start button and wait for Phoenix to simulate 1 frame so you can get a preview of the liquid particles.

Notice the water level. This is controlled by the Initial Fill Up parameter and it defaults to 50. 50 means 50% of the height/vertical size of the Phoenix Simulator. Set it such that the liquid particles barely cover the measurement box. In this example, an Initial Fill Up level of 25% is sufficient.

You may now run the simulation for a couple of frames to make sure everything is working as expected.

Under the Dynamics rollout, set the Steps Per Frame to 1.

The Steps Per Frame parameter is most useful when creating fast-moving / turbulent liquids. In the case of a ship moving through a calm liquid surface, the computational cost of higher SPF will have no benefit while slowing down the simulation. Higher Steps per Frame decrease the performance linearly - double the SPF means double the simulation time. For detailed information and examples, please check the Steps Per Frame documentation.

If you'd like to get a preview of the meshed liquid surface, head over to the Preview rollout of the Simulator and enable Show Mesh.

You may also disable the preview of entire groups of particles (such as Liquid, Foam, Splashes, etc.) from the Particle Preview section of the Preview rollout.

Let the simulation run for 100 or so frames and take note of the lack of interesting movement in the liquid at the back of the ship.

In real life, the liquid at the back of the ship is pushed backward by the propellers. The easiest way to emulate this effect is to simply use a box as a source geometry for a Phoenix Liquid Source - thus adding additional liquid and velocity into the simulation. Depending on the type of vessel you are creating and its size, you should tweak the placement and scale of the source geometry. If you're making a jetboat simulation, you may also try to give it a slight rotation so it points upwards.

Naturally, we want the box to move with the ship so it's placed in the same group as the ship geometry and the Phoenix Simulator.

Proceed by creating a Phoenix Liquid Source and specifying the box_liquid_source geometry as the emitter by placing it inside the Liquid Source's set.

Set the Discharge to 14. This parameter can be edited depending on the type of simulation. For a jetboat, the Discharge would be much higher than it is for a massive ship like the one in this example.

At the moment, the Liquid Source is pushing liquid in all directions. It may be hard to notice when the Discharge is set to a low value so check the example videos below.

To resolve this, you can tell the Phoenix Liquid Source to only emit based on certain criteria. In general, Phoenix provides you with 3 options:

1. Using a texture map.
2. Using only those faces which have a specific material applied to them.
3. Using a Discharge Modifier.

We go with the 2nd option, which is closest to the Polygon ID emission option on the Phoenix Source in 3ds Max.

Select the source geometry and go into Face Selection mode (F11). Select the face at the back of the ship and press&hold the Right Mouse Button to Assign New Material. Choose a Lambert material and change the Diffuse color to pink. Rename the new material to mat_liqSRC_EMIT.

The mat_liqSRC_EMIT material can now be specified under the Emit Material parameter of the Phoenix Source. The emission will now be limited only to those faces which share the specified material.

We are now ready to start setting up the Splash and Foam parameters for the Phoenix Simulator.

Open the Splash/Mist rollout and select the Enable Splash/Mist checkbox.

Choose Yes when asked if you'd like a Phoenix Particle Shader generated for the splash particles. This will automatically set up the link between the Splash Particle Group, the Particle Shader, and the Liquid Simulator.

Increase the Splash Amount parameter to 20. The Splash Amount controls both the size of the splash particles and their number.

In this example, the Birth Threshold is set to its default value of 10. However, keep in mind that you may want to increase it if the vessel you're using is moving faster. The Threshold controls where splash particles are generated and it is based on the curvature (how disturbed the surface is) of the liquid surface. If the Birth Threshold is low enough, even relatively flat areas of the liquid surface will produce splashes.

Set the Splash to Mist parameter to 0. Mist particles are a great way to add additional detail into the simulation but since the camera is rather far from the ship and they won't contribute much to the final shot, it would be a waste of time and resources to simulate them.

Set the Splash Air Drag to 5. As the name implies, this will add additional drag to the splash particles, causing them to travel a shorter distance. You may want to edit this parameter depending on the type of vessel you're simulating. For instance, if simulating a jetboat, this value would be best left at its default of 1.

Increase the Max Outside Age parameter. Here, it's set to 4. If a Splash particle leaves the Simulator and its outside life is set to 0, it will be instantly deleted. Because the simulation box in this example is quite short (small in the Y axis), it's possible many of the splash particles generated at the front of the ship will rise high enough to leave the bounds of the Simulator and be deleted.

Increase the Liquid-Like to 1. This parameter controls the behavior of splash particles in the air. If the value is set to 0, they will behave as individual points in empty space. Increasing this value will force the particles to try and stick to each other, thus forming tendrils when ballistic.

Open the Foam rollout and select the Enable checkbox.

Choose Yes when asked if you'd like a Phoenix Particle Shader generated for the foam particles. This will automatically set up the link between the foam Particle Group, the Particle Shader, and the Liquid Simulator.

Set the Foam Amount to 0. This will disable the algorithm responsible for directly generating foam from the liquid surface.

In this example, we generate the Foam from the Splash particles using the Foam on Hit parameter in the Splash/Mist rollout.

In the Foam rollout, set the Foam Amount to 0. This will disable the algorithm responsible for directly generating foam from the liquid surface. In this example, we generate the Foam from the Splash particles using the Foam on Hit parameter in the Splash/Mist rollout.

Set the Half Life parameter to 1.5. This option sets the time required for the particles to reduce to half of their initial count, in seconds. Affects only the foam bubbles above the liquid surface.

Increase the Max Outside Age parameter to 3. As mentioned earlier, the foam can live outside the bounds of the Phoenix Simulator - setting this parameter to 3 (seconds) ensures that the foam lives long enough to accumulate in the ship's path.

Set the Size to 0.05m. The Size parameter controls the size of the foam bubbles. Even though a real-life foam bubble is obviously not 5cm wide, here we can afford to use larger and fewer foam particles (because this is a distant shot) in order to optimize the sim. Foam Size works in conjunction with the B2B Interaction (B2B stands for Bubble to Bubble). For instance, a large bubble size coupled with high B2B Interaction will cause the particles to start colliding and pushing each-other - this can be very useful for simulating beer or bathtub foam.

Set the Size Variation Small / Large to 0 and 5 respectively, and the Distribution to 300. Those 3 parameters work with the Foam Size - with these settings, the largest bubbles will be no bigger than Size * 5, and the distribution will be such that there will be 300 times more average-sized bubbles than large bubbles.

Reduce the B2B Interaction to 0. This can be an expensive effect that is really not necessary for this type of simulation.

Set the Rising / Falling Speed to 0.5m and 5m respectively. Those parameters control the vertical speed of the foam particles.

Set Surface Lock to 0.5. This allows you to control the behavior of the foam inside the liquid. If the Surface Lock is set to 1, the foam will be forced to float exactly at the liquid surface, regardless of any motion that may otherwise temporarily force it to sink into the water. Setting it to 0 disables this behavior and the values in-between act as a multiplier for the effect.

Set the Patterns Strength to 0.5 and the Patterns Radius to 1.5m. Those 2 parameters control the Phoenix algorithm responsible for generating foam patterns over the liquid surface.

Open the Splash/Mist rollout and set the Foam Amount to 2. This will cause Foam particles to be generated when the Splash particles collide with the liquid surface.

Also, set the Depth to 4. The Depth parameter controls how far below the surface the Foam particles are born.

Under the Liquid rollout, set the Droplet Surfing parameter to 0.6.

The Droplet Surfing option controls how long a particle separated from the main body of water will hover on the surface before it merges with the liquid. Increasing this parameter allows the Splash particles to slide along boat wake thus producing a wider trail of foam in the front of the ship.

The simulation parameters should all be set up now.

Increase the resolution of the grid to ~100 000 000 voxels by reducing the Grid → Cell Size parameter (0.14 in the example scene).

Let the entire simulation cache to disk. This may take a while depending on the speed of your machine.

Let's start by setting up the options in the Rendering rollout of the Phoenix Simulator.

Set the Mode to Ocean Mesh. If Preview → Show Mesh is enabled, this should generate a preview of the liquid ocean inside the camera's frustum. The Ocean Mesh mode generates a liquid surface from the boundaries of the Phoenix Simulator box.

The Ocean → Ocean Level parameter needs to be adjusted as well.

Recall that we used the Liquid → Initial Fill Up parameter to set the initial liquid level for the Simulator. The Initial Fill Up is a simulation setting and cannot be altered without Simulating again. The Ocean Level, on the other hand, is a rendering setting which you can freely edit at any point. It allows you to compensate for the liquid particles subsiding or going above the Initial Fill Up level during the simulation. The Ocean Level might not exactly match the Initial Fill Up level, even when set to the same value, and you will notice such mismatch right at the boundaries of the Phoenix Simulator where the generated infinite ocean connects with the Simulator's liquid surface. Because there are many situations where an automated solution might fail (such as the infinite ocean surface oscillating up and down until it settles which will cause the horizon to bounce), it is left to you to match the Ocean Level to its best value.

The easiest way to do this is to enable the Mesh Preview (Preview rollout) and start with the same value as the one set for Initial Fill Up in the Dynamics tab. Then, looking at the mesh preview, increase or decrease the Ocean Level in small increments until the generated ocean is leveled with the surface generated by the Simulator.

Open the Rendering → Mesh rollout and set the Ocean Level parameter to the same value as the Liquid → Initial Fill Up parameter.

If the border between the Simulator and the generated mesh is still visible, increase/decrease the Ocean Level in small increments until the generated surface is smooth.

In this example, the Ocean Level is set to 25.

Under the Rendering → Displacement rollout, enable Displacement by clicking the checkbox to the right of the Displacement Amount parameter.

Plug a Phoenix Ocean Texture in the Displacement → Texture slot.

Be sure to set the displacement Type to Vector. Vector displacement is used to move the surface vertices along arbitrary directions using the Red, Green and Blue components of the input texture, while the regular Gradient / Surface driven displacement can only displace the surface along the surface normal.

Below are the settings for the Phoenix Ocean Texture:

Set the Wind Speed parameter to 5. The Wind Speed parameter will affect the height of the waves. A higher wind speed creates bigger waves and vice versa.

The Wave Height is set to 1, with Sharpness of 1, Velocity Coherence of 0 and Wave Crest of 0. You can find more information on those options in the Phoenix Ocean Texture documentation.

If you'd like to rotate the direction of the waves generated by the Phoenix Ocean Texture, tweak the Rotate Y parameter of the the place3dTexture node connected to the Phoenix Ocean Texture.

Create a V-Ray Material and assign it to the Phoenix Simulator.

Set the Diffuse color to RGB: [0, 0, 0].

Reflect and Refract colors should be set to RGB: [255, 255, 255] - this will produce a completely transparent material if the Index of Refraction was set to 1 (which is the IOR of clear air).

Set the Refraction IOR to 1.33 - this is the physically accurate index of refraction of water.

If you were to hit render now, you'd notice that the water is completely transparent and certainly does not look like an ocean.

To resolve this, set the Fog color to RGB: [180, 220, 220] and reduce the Depth to 20000. This should produce the type of shading you'd expect in a large body of water containing all sorts of particulates that interfere with the light rays.

The provided scene file contains a V-Ray Infinite Plane already prepared for you. You can simply unhide it and you'll be good to go.

However, if you're working with a different file, you should create a V-Ray Plane and assign a simple diffuse V-Ray Material to it. Place it below the level of the water. In this example, it's translated to -50m in Z.

Here's why this is needed: the Fog Color parameter of the V-Ray material won't affect the Phoenix Particle Shaders (with a Liquid Simulator connected) unless the 'volume' of the liquid is capped. This is a V-Ray peculiarity that occurs because the Ocean Mesh / Cap Mesh rendering modes produce a one-sided sheet of geometry which isn't closed off like the regular Mesh mode.

So, if the mesh is not 'closed off' by some other geometry in the scene (such as a V-Ray Plane), the underwater particles will not be shaded with the Fog Color of the V-Ray Material.

Furthermore, flickering in the particles may occur when rendering out a sequence.

Select the Phoenix Foam Particle Shader and set the Mode to Points. The default option of Bubbles is better suited for close up shots. As the camera is far away from the ship, generating and rendering the bubbles is a waste of resources.

The Color is set to RGB: [181, 181, 181]. This is done so the foam doesn't appear too bright which will kill the detail - you are free to edit this value based on the requirements of your shot.

The Size Multiplier is set to 4. The Size options in the Particle Shader allow you to edit the Foam particle size after a simulation is complete. There is nothing stopping you from keeping this value at 1 and increasing the Foam Size in the Foam rollout of the Liquid Simulator instead, but that would require a re-run of the entire simulation.

If turned on, uncheck Disable Liquid Shadows. This option controls the lighting of the underwater foam particles. When Liquid Shadows are disabled, the foam particles inside the liquid are not tinted by its material's Fog Color. We'd like to get this tinting effect for additional realism.

The Scattering option is set to Approximate + Shadows. The Approximate+Shadows options allows the for the foam to drop shadows over solid geometry in the scene.

The Motion Bur is set to From Renderer. The current renderer's own Motion Blur setting will be used.

You may want to decrease the Light Cache Speedup in case you notice flickering in the rendered animation. In this example, the value is set to 0.9. The Light Cache Speedup can significantly reduce the render times.

Open the Point rollout of the Foam Particle Shader and set the Point Alpha parameter to 0.017.

The Point Size is set to 0.5. (If using Phoenix 4 or later, please set this value to 0.35).

This change will give a smoother appearance to the foam particles - the lower Alpha value will allow them to blend together and also reveal some of the liquid underneath.

The Motion Blur Step is set to 1. Motion blur in Point mode is calculated by cloning the particle several times and placing those copies along the particle trajectory. This parameter controls the distance between the copies. The smaller the step, the higher the quality, though at the cost of render time. Since the Motion Blur option is set to Force off, you can safely skip this step. However, if you eventually decide to render the Foam with Motion Blur, experiment with this option to find the best result for your scene.

Repeat the same changes for the Phoenix Splashes Particle Shader.

Because there is a large number of splash particles born at the ship's front, having no Motion Blur may cause the rendered animation to look unnatural.

Consider enabling Motion Blur for the Splash Particles Shader by settings the Rendering → Motion Blur option to Force On. Keep in mind that this will slow V-Ray down a bit.

The provided scene file contains a V-Ray Sun & Sky setup.

You can find the VRay Sky texture in the Hypershade.

The Intensity multiplier is set to 0.06.

Turbidity is set to 3.0.

The Sky Model is set to Preetham et al.

The Ground Albedo is set to RGB: [51, 51, 51].

Blend angle set to 5.739.

Invisible is enabled so the Sun does not produce noisy specular highlights over the ocean's surface.

The Shadow bias is set to 0.04m.

The Photon emit radius is set to 10.0m.

The sun is positioned relatively low on the horizon to produce yellow-ish illumination that is balanced by the blue lighting provided by the VRay Sky texture.

The Photometric Lights Scale under V-Ray Render Settings → Overrides → Lighting is set to 0.002. This is done to compensate for the change of the default Maya units (centimeters) to meters. Increasing the Lights Scale will increase the apparent intensity of all lights in the scene.

Set the V-Ray Sampler type to Bucket.

Set the Min subdivs to 1 and the Max subdivs to 12.

Set the Noise threshold to 0.01.

Set the Render region divison to 16.

Navigate to the GI tab and enable the Global Illumination.

Set the Light cache Subdivs to 1000.

Without GI

With GI