Avalanche

The setup for this tutorial requires Phoenix 5.20.00, V-Ray 6 for 3ds Max 2020, Chaos Scatter 2.5 and tyFlow FREE v1.023 or newer. You can download official Phoenix and V-Ray builds 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.

We will be creating two shots: one full shot, serving as an establishing shot, and a close-up shot that allows viewers to feel the impact of the avalanche.

The sample scenes provide you with the terrain and winter trees from Chaos Cosmos, populated with the help of Chaos Scatter. We use tyFlow's particles as a source to generate and simulate smoke, creating an avalanche effect with Phoenix.

For the close-up, we add an extra layer of smoke, apply camera shake, and some animated trees to enhance the visuals.

At the end of the tutorial, we color correct the image with V-Ray Frame Buffer, and we make the shot more cinematic by using Light Mix. It allows us to adjust the key-to-fill light ratio without rendering the image again.

The Download button below provides you with an archive containing the scene files.

Download Project Files

Scale is crucial for the behavior of any simulation. Large-scale simulations appear to move slower, while medium and small-scale simulations display lots of vigorous movement. When you create your Simulator, have a look at the Grid rollout where the real-world size of the Simulator is shown. If it 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.

The Phoenix solver is not affected by how you choose to view the Display Unit Scale - it is just a matter of convenience.

This is the top view of the final scene for the full shot, which includes the following elements:

1. PHXTurbulence force to disturb the avalanche;
2. PHXSource using the tyFlow_avalanche node as an emitter;
3. Phoenix Fire / Smoke Simulator  - PhoenixFDFire_avalanche for simulating the smoke as avalanche;
4. Phoenix Fire / Smoke Simulator  - PhoenixFDFire_fog for rendering the fog;
5. VRayCam_Full-shot camera for rendering;
6. V-Ray Sun & Sky setup for lighting;
7. GeoSphere001_Cloud, GeoSphere002_Cloud and GeoSphere003_Cloud for casting shadows over the winter mountain;
8. Terrain geometry;
9. Terrain_for_Position_Object for the source emitter for the tyFlow_avalanche;
10. tyFlow node: tyFlow_avalanche for emitting particles;
11. Terrain_lowpoly_collision geometry used as collision object for the tyFlow particles;
12. The Box_kill-box provides a region to define where the tyFlow particles penetrate the Terrain_lowpoly_collision and will be removed;
13. Two trees from Chaos Cosmos: Spruce Tree Snow 98-14 and Spruce Tree Snow 98-16;
14. A Chaos Scatter object to scatter the Spruce Tree Snow 98-14 and Spruce Tree Snow 98-16 over the Terrain geometry;
15. Line01~06 are used to define the region that the terrain uses to scatter trees. 

This is the top view of the final scene for the close-up shot, which includes the following elements:

1. PHXTurbulence force to disturb the avalanche;

2. PHXSource using tyFlow_avalanche as an emitter;

3. Phoenix Fire/Smoke Simulator  - PhoenixFDFire_avalanche for simulating the smoke acting as an avalanche;

4. Phoenix Fire/Smoke Simulator  - PhoenixFDFire_ground-smoke simulating the ground smoke acting as snow over the ground;

5. Phoenix Fire/Smoke Simulator  - PhoenixFDFire_fog for rendering the fog;

6. VRayCam_Close-up camera for rendering;

7. Dummy_camera-shake (not shown in the screenshot) is a dummy object with a Noise controller applied to its position. VRayCam_Close-up.Target is linked to this dummy to create the camera shake effect;

8. V-Ray Sun & Sky setup for lighting;

9. Terrain geometry;

10. Terrain_push geometry;

11. Terrain_for_Position_Object for the source emitter for the tyFlow_avalanche;

12. tyFlow node: tyFlow_avalanche;

13. Terrain_lowpoly_collision geometry used as collision object for the tyflow particles;

14. Box_kill-box provides a region to define where the tyFlow particles which penetrate the Terrain_lowpoly_collision geometry will be deleted;

15. Two trees from Chaos Cosmos: Spruce Tree Snow 98-14 and Spruce Tree Snow 98-16;

16. A Chaos Scatter object to scatters the Spruce Tree Snow 98-14 and Spruce Tree Snow 98-16 over the Terrain geometry;

17. Line01~06 are used to define the region that terrain uses to scatter trees;

18. Alembic_leaf, Alembic_snow, and Alembic_stem are animated trees stored in Alembic file format, specifically crafted to enhance the visuals for the close-up shot.

As tyFlow particles penetrate the terrain, those within the Box_kill-box are deleted by the tyFlow's Surface Test (inside) operator. It's worth noting that the Box_kill-box is rotated at a 17-degree angle on its X-axis to align with the Terrain geometry.

All the helper geometries used in the scenes, including Terrain_lowpoly_collision, Box_Kill-box, Terrain_for_Position_Object, Terrain_ground_smoke and Terrain_Push, have their Object Properties set to Display as Box and Renderable disabled. This configuration ensures that they remain unobtrusive in the viewport and are not visible in the final rendering.

In scenes involving collision in tyFlow or Phoenix simulations, such as Terrain_lowpoly_collision, Terrain_ground_smoke, and Terrain_Push, all the helper geometries have a Shell modifier added.

The purpose of this Shell Modifier is to give volume to the planes by transforming them into actual 3D shapes with thickness. This added thickness ensures precise particle collision. Furthermore, in order to get predictable Phoenix simulation results it's best to use closed geometry objects.

Click on the Time Configuration icon ( ) and set the Animation Length to 180, so that the Time Slider goes from 0 to 180.

Disable both the Real-Time and Loop options.

Shot 01 - Full shot

This is the establishing shot in which you see the avalanche from a distance, with winter trees scattered across the terrain. We limit the distribution of the trees to keep them out of the valley. This approach not only enhances the overall realism of the forest but also ensures that the trees do not obstruct the path of the avalanche.

Since the forest in this shot is static, it can seem rather boring. To address this, we introduce three dynamic spheres positioned above it as clouds. These spheres cast shadows onto the forest, infusing vitality and depth into the entire scene.

Shot 02 - Close-up

In close-up shots, the avalanche approaches the camera head-on. To heighten the impact, we incorporate dynamic trees and introduce blowing snow on the ground. This snow constantly moves toward the camera, amplifying the visual intensity.

Let's begin by focusing on Shot 01.

Open the scene file Avalanche_shot01_max2020_start.max, which includes terrain, tyFlow, and other essential components to get started. Our initial task is to distribute winter trees across the mountain.

Open Chaos Cosmos browser and use the search bar to look up for trees and spruce. You'll find two relevant models for creating a winter forest: Spruce Tree Snow 98-16 and Spruce Tree Snow 98-14. Download these models and import them into your scene.

Move the trees to the side to ensure they are not visible from the camera's perspective.

The exact position of Spruce Tree Snow 98-16 in the scene is XYZ: [ -465.0, -149.0, -23.0 ].

The exact position of Spruce Tree Snow 98-14 in the scene is XYZ: [ -465.0, -233.0, -23.0 ].

Navigate to the Create panel and select the Geometry tab. From the drop-down menu, select Chaos Scatter and create a Chaos Scatter in the scene.

With the Chaos Scatter selected, in the Objects rollout, use the "+" button to add Terrain to the Distribute-on target objects list. Then add the Spruce Tree Snow 98-16 and Spruce Tree Snow 98-14 to the Instanced model objects list. 

• In the Scattering rollout, check the Enable option. Set the mode to 2D -On surfaces.
• Enable Avoid collisions. Set the Spacing[%] to 50.0. This can avoid the tree overlapping.
• In the Surface Scattering rollout, Set the Random distribution Count to 50000.
• Set the Slope Limitation Angle from 0.0 to 30.0.
• In the Rotation section of the Transformations rollout, set the Z Rotation To to 360.0.
• To randomize the trees, in the Transformations rollout, set the Normal to Z to 0.95.
• In the Scale[%] section, set X From and To to 70.0 and 120.0, respectively.
• In the Areas rollout, use the "+" button to add Line01~06. By doing this, the tree asset is scattered within the enclosed region defined by those splines.
• In the Viewport Display rollout, set the Previz type to Box.

Go to Create Panel → Create → Geometry → PhoenixFD → FireSmokeSim. Rename the simulator to PhoenixFDFire_avalanche.

The exact position of the Phoenix Simulator in the scene is XYZ: [107.4, 44.7, 68.7 ].

The exact rotation of the Phoenix Simulator in the scene is XYZ: [ 17.0, 0.0, 0.0 ].

Open the Grid rollout and set the following values:

With the Simulator selected, navigate to the Scene Interaction rollout. Since there are many objects in the scene, in order to avoid any unwanted interactions, switch to the Include List and add PHXSource, tyFlow_avalanche, and Terrain_lowpoly_collision to the list. This way the simulation will interact only with the objects in the Include list.

Select the Phoenix Simulator → Output rollout and enable the output of Grid Smoke, Grid Wavelet and Grid Velocity Channel. 

Create a Phoenix Fire/Smoke Source in the scene: Create Panel → Create → Helpers → PhoenixFD → PHXSource.

Press the Add button to choose which geometry to emit from and select the tyFlow_avalanche entry in the Scene Explorer.

After adding the tyFlow_avalanche to the Emitter Nodes of the PHXSource, let's disable the Temperature channel since we won't need it in this simulation. Leave everything else at the default settings for now.

To focus on the fluid simulation task, we begin by hiding the Chaos Scatter object in the scene.

Additionally, clicking the Play Animation button prompts tyFlow to automatically cache the particle animation in the system memory. Once cached, you find a purple bar in the timeline. Caching the particles can enhance the efficiency of the Phoenix fluid simulation.

If for any reason, the particle animation in tyFlow doesn't cache properly, you can resolve this by opening the tyFlow Editor and by clicking the upper right button to clear the cache. Then click the Play Animation button to recache.

Select the Simulation rollout of the Simulator. Press the Start button to simulate.

This is a voxel preview of the current animation. The result is what looks like thick smoke billowing upwards.

With the Simulator selected, in the Dynamics rollout change the Fluidity Method to PCG Symmetric, with a Quality of 50.

The PCG Symmetric option is the best method for smoke or explosions in general, preserving both detail and symmetry. The high Conservation Quality allows the smoke to swirl better. For more information, visit the Conservation documentation.

Select the PHXSource in the scene, switch the Emit Mode to Volume Brush. This mode fills the entire volume of the emitter objects with fluid. As particles flow down the hill, this makes it more suitable for simulating avalanche effects than Surface Force.

With those new settings, run the simulation again.

This is a voxel preview of the current animation. While the simulation behaves more like an avalanche now, it appears somewhat weak.

With the PHXSource selected, increase Smoke amount to 3.0. Increase Motion Vel. to 3.0. As for the Particle Shape, switch it to Sphere and set a custom size of 0.7 meters.

With those new settings, run the simulation again.

This is a voxel preview of the current animation. While there is now a more robust smoke presence, there still isn't the desired avalanche dynamics with snow accumulating downward.

To make the smoke sink down, select the Fire/Smoke Simulator, navigate to the Dynamics rollout, and set the Smoke Buoyancy to -1.0.

With these updated Dynamics settings, rerun the simulation.

This is a voxel preview of the animation.

To bring more realism to the avalanche, let's add some forces to the scene. In order to give the smoke even more details, we add Phoenix Turbulence in order to introduce some turbulence in the fluid.

Go to the Create panel > Helpers > PhoenixFD and click on PHXTurbulence. Create a Phoenix Turbulence in the scene.

As we add the Phoenix Turbulence to the scene, make sure you add it to the Scene Interaction Include List of the Simulator, too; otherwise, the force won't have any effect.

Run the simulation again.

This is a voxel preview of the current animation. Now more details in the avalanche start to appear.

Open the Phoenix Simulator → Resimulation rollout and enable Grid Resimulation.

Note that when you enable Resimulation, Phoenix reads the cache files for preview and rendering from the Resimulation Output Path, instead of the regular Output. Don't worry if the Viewport goes blank and the preview disappears - you can always go back to the original cache files by disabling the Resimulation.

Set the Amp.Resolution to 1.0. This parameter is used to increase the resolution of the grid during the Resimulation process.

Set Amp. Method to Wavelet Nice and Wavelet Strength to 10.0.

Press Simulator → Simulation rollout → Start to begin the Resimulation.

This is a voxel preview of the current animation. As you can see, after the Resimulation, we get more details in the avalanche, while maintaining the overall pattern formation from the base simulation.

Run a test render from frame 165. It helps us assess what changes are needed to improve the look of the shading.

Select the Simulator, and go to its Volumetric Render Settings.

Increasing the value for Light Cache Speedup speeds up the render, but it also lowers the quality of the Volume Light Cache. If dark cubic grid artifacts start forming on the smoke, the parameter is set too high. For more information, visit the Volumetric Rendering In-Depth page.

In this case, disable the Volume Light Cache, as it produces cleaner render result.

Alternatively, you can load up a render preset from the Avalanche_render_preset.tpr file, that is provided in the sample scene.

With the new volumetric settings, run a test render from frame 165. The avalanche shading has been improved for a more realistic look, but to enhance the scene's atmosphere, we aim to introduce fog in the next step.

In order to simulate the fog in the scene we can use a Fire/Smoke Simulator instead of a V-Ray Environment fog.

Let's create one now. Go to Create Panel > Create > Geometry > PhoenixFD > FireSmokeSim. Rename it to PhoenixFDFire_fog.

The exact position of the Phoenix Simulator in the scene is: XYZ: [ -22.0, 0.0, 0.0 ].

Open the Grid rollout and set the following values:

Select the Phoenix Fire/Smoke Simulator, and go to its Volumetric Render Settings.

Let's unhide Chaos Scatter and run a test render with the newly added ambient fog. Now, you can observe a convincing avalanche flowing down the valley amidst white snow and a wintry forest. It just requires some color correction.

In the Render Setup > Render Elemets tab, add VRayLightMix render elements. This is necessary for relighting the scene in the VFB.

Open the V-Ray Frame Buffer and use the Create Layer icon ( ) to add layers for Exposure, White Balance and Filmic Tonemap.

The image is rendered using the V-Ray Frame Buffer. In the current example, the color corrections and post effects are set to:

Filmic Tonemap:

White Balance:

Exposure:

Lens Effects:

Feel free to use other values for the post effects, depending on your preferences.

This step shows how to use LightMix to adjust the keylight (VRaySun) to fill-light (VRaySky) ratio. Reducing the weight of VRaySun and adjusting the color of both VRaySun and Environment contributes to a more cinematic shot.

Select the Source: LightMix layer and switch its mode from RGB to LightMix.

Alternatively, you can load up a layer tree Preset from the Avalanche_VFB.vfbl file that is provided in the sample scene.

Here is the final rendered result (from frame 90 to frame 180) for Shot01 of the avalanche scene.

Now that we have completed Shot 01, we can begin working on Shot 02. Open the scene file Avalanche_shot02_max2020_start.max, which includes terrain geometries, tyFlow, scattered trees with Chaos Scatter, and other essential components to get started.

Go to Crete Panel → Create → Geometry → PhoenixFD → FireSmokeSim. Rename the simulator to PhoenixFDFire_avalanche.

The exact position of the Phoenix Simulator in the scene is XYZ: [107.4, 44.7, 68.7 ].

The exact rotation of the Phoenix Simulator in the scene is XYZ: [ 17.0, 0.0, 0.0 ].

Open the Grid rollout and set the following values:

In the Dynamics rollout of the Simulator, inherit the settings from shot 01. 

• Set the Smoke Buoyancy to -1.0.
• Set the Fludity Method to PCG Symmetric, Quality to 50.

With the Simulator selected, navigate to the Scene Interaction rollout. Since there are many objects in the scene, in order to avoid any unwanted interactions, switch to the Include List and add PHXSource, tyFlow_avalanche, and Terrain_lowpoly_collision to the list.

Select the Phoenix Simulator → Output rollout and enable the output of Grid Smoke, Grid Wavelet and Grid Velocity Channel. 

Create a Phoenix Fire/Smoke Source in the scene: Create Panel → Create → Helpers → PhoenixFD → PHXSource. Rename it to PHXSource_avalanche.

Press the Add button to choose which geometry to emit and select the tyFlow_avalanche entry in the Scene Explorer.

Set up the PHXSource_avalanche's properties:

Select the Simulation rollout of the PhoenixFDFire_avalanche Simulator. Press the Start button to simulate.

Here's a voxel preview of the current animation.

Shot02 shares the same Volumetric Shading setup as shot01, so there's no need to set it up from scratch. You can load up a render preset from the Avalanche_render_preset.tpr file, that is provided in the sample scene.

Here is a test render of frame 110. You can see a visible gap between the avalanche and the terrain.

With the PHXSource_avalanche selected, increase the Noise to 0.5.

With the PhoenixFDFire_avalanche Simulator selected, go to the Scene Interaction rollout. Remove Terrain_lowpoly_collision from the Include List and add Terrain_Push to the list.

With the new settings, let's run the simulation again.

This is a voxel preview of the current animation.

Here is a test render of frame 110.

Open the Phoenix Simulator → Resimulation rollout and enable Grid Resimulation.

Note that when you enable Resimulation, Phoenix reads the cache files for preview and rendering from the Resimulation Output Path, instead of the regular Output. Don't worry if the Viewport goes blank and the preview disappears - you can always go back to the original cache files by disabling the Resimulation.

Set the Amp.Resolution to 1.0. This parameter increases the resolution of the grid during the Resimulation process.

Set Amp. Method to Wavelet Nice and Wavelet Strength to 10.0.

Select the Simulator → Simulation rollout → Start to begin the Resimulation.

This is a voxel preview of the current animation.

After resimulation, run a test render of frame 110.

Now that we have achieved the primary avalanche effect for shot 02, in order to enhance its visual impact, let's also create an additional smoke effect that emits snow from the ground and directs it towards the camera.

Go to Create Panel → Create → Geometry → PhoenixFD → FireSmokeSim. Rename the simulator to PhoenixFDFire_ground-smoke.

The exact position of the Phoenix Simulator in the scene is XYZ: [ -8.5, 0.25, 0.0 ].

The exact rotation of the Phoenix Simulator in the scene is XYZ: [ 17.0, 0.0, 0.0 ].

Rename it to PhoenixFDFire_ground-smoke.

Open the Grid rollout and set the following values:

Select the Phoenix Simulator → Output rollout and enable the output of Grid Smoke and Grid Velocity Channel. 

Create a Phoenix Fire/Smoke Source in the scene: Create Panel → Create → Helpers → PhoenixFD → PHXSource. Rename it to PHXSource_ground-smoke.

Press the Add button to choose which geometry to emit and select the Terrain_ground-smoke entry in the Scene Explorer.

The Terrain_ground-smoke has Edit Poly and Shell modifiers applied.

The purpose of the Shell Modifier is to give the plane volume by turning it into an actual 3D shape with thickness. In order to get predictable simulation results using Phoenix it's best to use shelled, closed geometry.

Within the Edit Poly modifier, we specifically select the top side of the terrain and assign a face ID of 1, while the remaining faces are assigned a face ID of 2. This setup enables us to restrict fluid emission to only one side of the mesh.

Set up the PHXSource_ground-smoke's properties:

Enable 3ds Max Auto Key Mode. Set the new tangent type keyframes to Linear. At frame 0, set the X Offset of Noise_for_ground-smoke to 0. At frame 180, set the X offset to 60.0.

Enable 3ds Max Auto key frame. Set the new tangent type keyframes to Linear. At frame 0, set the X Offset of Noise_for_ground-smoke to 0. At frame 180, set the X offset to 60.0.

Go to Graph Editors/Track View → Curve Editor and find the keyframes of Offset for the Noise_for_ground-smoke.

Each frame and value used in this tutorial are shown in the screenshots.

Create a Phoenix Plain Force , a simple directional force, to simulate the effect of wind.

Go to Create Panel > the Helpers tab > Phoenix and add a Phoenix Plain Force.

With the PhoenixFDFire_ground-smoke selected, navigate to the Scene Interaction rollout. Add PlainForce001 to the Include List.

With the new Plain Force and the PHXSource_ground-smoke in the scene, let's run the simulation again.

This is a voxel preview of the current animation.

Again, PhoenixFDFire_ground-smoke in Shot02 shares the same Volumetric Shading setup as shot01, so there's no need to set it up from scratch. You can load up a render preset from the Avalanche_render_preset.tpr file, that is provided in the sample scene.

In order to simulate the fog in the scene we can use a Fire/Smoke Simulator instead of a V-Ray Environment fog. This way we can avoid blending issues between the Phoenix Simulators and V-Ray Environment fog and skip using the slower Volumetric Geometry Mode for the rendering.

Let's create one now. Go to Create Panel > Create > Geometry > PhoenixFD > FireSmokeSim. Rename it to PhoenixFDFire_fog.

The exact position of the PhoenixFDFire_fog in the scene is: XYZ: [ 135.0, -2.6, 21.3 ].

The exact rotation of the PhoenixFDFire_fog in the scene is XYZ: [ 17.0, 0.0, 0.0 ].

Open the Grid rollout and set the following values:

Select the PhoenixFDFire_fog and go to its Volumetric Render Settings.

Now that we have all the elements necessary for shot 02, unhide ChaosScatter, Alembic_leaf, Alembic_snow, Alembic_stem, and all the Simulators in the scene. Let's run a final preview before rendering.

This is a voxel preview of the current animation.

In the Render Setup > Render Elemets tab, add VRayLightMix render elements. This is necessary for relighting the scene in the VFB.

Shot02 shares the same color correction settings as shot01, so there's no need to set it up from scratch. In the V-Ray Frame Buffer, click Load Layer Tree Preset...

...and load the Avalanche_VFB.vfbl file that is provided in the sample scenes.

Here is the final rendered result (from frame 120 to frame 180) for Shot02 of the avalanche scene.

We now have sequences of avalanche scenes for both the full shot and the close-up. You can utilize any editing software to produce the complete animation.