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Requires Phoenix 3.10.00 Official Release and V-Ray 3.60.04 Official Release for 3ds Max 2015 or newer. 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 Burning Chair effect using Phoenix and 3ds Max.

The emission of fire is modulated by a VertexPaint modifier coupled with a Vertex Color texture used as a mask for the Phoenix Fire Source. Many Dynamics parameters related to Fire/Smoke simulations are explained in detail, with videos showing their effect on the simulation. The simulation is then written to disk, and the resulting cache files are used for the Phoenix Resimulation process to slow down the movement of the flames.

The Download button below provides you with an archive containing the start and end scenes, as well as a Phoenix Render Settings preset that you can use to quickly set up the volumetric shading options for a basic fire simulation.

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.

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

A burning piece of furniture would be considered a small-scale simulation so we will view the units as Centimeters.

Go to Customize → Units Setup and set Display Unit Scale to Metric Centimeters.

Also, set the System Units such that 1 Unit equals 1 Centimeter.

The final scene consists of the following elements:

1. The chair geometry with a VertexPaint modifier.
2. A Phoenix Fire/Smoke Source with the chair geometry in its list. A Vertex Color texture is used as a Mask for the Outgoing Velocity parameter of the Source. The Vertex Color texture is reading the vertex data from the Vertex Paint modifier on the chair geometry. The Source is also emitting Drag Particles into the simulation. The Drag particles are used to represent embers.
3. A Phoenix Fire/Smoke Simulator for the fire.
4. A Phoenix Plain Force used to imitate wind blowing in the positive X direction.
5. A Phoenix Particle Shader to render the Drag Particles of the Source as points.
6. A V-Ray Infinite Plane for the ground.

Set the Time Configuration → Animation Length to 60 so that the Timeslider goes from 0 to 60.

If you need any geometry animation that should interact with the simulation, prepare the animation at this step. After we're done with the basic simulation, we will rescale the timeline to slow down any animation present in the scene and we will use the Resimulation option to slow down the fire simulation as well.

Select the chair geometry and left-click on the Burning Fuel with Smoke preset from the Phoenix Toolbar.

This will generate an entire setup for you consisting of a Phoenix Fire/Smoke Simulator, a Phoenix Fire Source, and a Phoenix Particle Shader node used for rendering the Drag particles produced by the source.

Phoenix provides a high-quality GPU Preview directly in the 3ds Max Viewport which should be enabled by default by the Burning Fuel preset.

You may want to disable it if you're working through a Remote Desktop connection or on a machine with integrated graphics.

To do so, go to the Preview rollout → GPU preview section → Enable in Viewport.

Here's how the simulation looks with the default Burning Fuel preset.

As you can see from the video to the right, there are plenty of issues to address:

1. The emission is uniform - the entire chair is burning instead of only certain sections of it. We will first take care of that by using a VertexPaint modifier to specify where the emission happens.
   
   
2. The fire is too choppy - we are going for a smoother/calmer look. The noisiness in the fire is caused by the low grid resolution, the Vorticity parameters in the Dynamics rollout of the Simulation, and to a lesser extent - the shading settings set up in the Rendering → Volumetric Options → Fire window. We resolve this by disabling the Vorticity parameters and tweaking the Fire rendering Color and Intensity curve of the Volumetric Shader.
   
   
3. The fire is moving rather quickly - this would be the desired behavior when simulating a burning flammable fluid but instead we would like to achieve a smoother flame. Think of a campfire - the flames produced by the Burning Fuel preset don't resemble the calm and elongated fire produced by burning wood. We resolve this by slowing down the cached sequence from the Input panel and resimulating over the slowed-down cache files with the Time-Bend Resimulation option enabled.

Select the chair geometry and apply a VertexPaint modifier. A VertexPaint toolbar should appear in the 3ds Max UI. If you accidentally close it, use the Edit... button under the VertexPaint modifier to bring it back.

Click the left-most icon at the top of the toolbar to set the Vertex Color display to Unshaded - this makes it easier to see what you're doing.

Then, set the Color to Black (0, 0, 0) and use the Paint Bucket icon to make the entire chair black.

Activate the Brush tool, set the Color to White (255, 255, 255) and paint the areas that you want to be burning.

When finished, click the 3-rd icon (left to right) at the top to disable the vertex color preview.

Open the Material Editor and create a Vertex Color texture. The Vertex Color texture can read the color information that we just painted on the chair geometry.

You can directly pipe its output into the Outgoing Velocity Mask of the Phoenix Source.

However, in this tutorial, we add additional variation by compositing the Vertex Color texture over a Cellular texture using a VRayComp texture.

Add a VRayComp texture and feed the output of the Vertex Color to the SourceA input.

Set the Operator to Multiply (A*B).

Then, add a Cellular texture and feed its output to the SourceB input of the VRayComp texture.

Left-Mouse-Button click and drag from the VRayComp texture's output to the Outgoing Velocity Mask parameter of the Phoenix Fire Source.

The painted Vertex Color on the chair geometry will heavily affect the simulation result. You can always go back to the VertexPaint modifier and tweak the color.

Set the Cellular type to Circular, with a Size of 2.0 and a Spread of 0.25. Those values are an artistic choice and in no way set in stone - feel free to change them if your setup requires it.

Animate the Offset X parameter to go from a value of 0 to 5 over the range of frames 0 to 60. This will cause the sampling coordinates for the Cellular noise to shift over time, adding one more layer of randomness to the emission.

Open the Curve Editor and set the tangents for the animation to Linear.

If you can't find the Cellular texture coordinates in the list, make sure to disable the Show Only filters under the View → Filters options box. You should then be able to find it under SME → Map # → Properties → Coordinates.

This is done so the animation of the Cellular noise doesn't speed up in the beginning and slow down at the end, which is the effect of the default Ease In - Ease Out tangents.

Here's how the simulation looks with the VRay Comp texture used as a Mask for the Outgoing Velocity.

We still need to tweak the simulation parameters and make some speed optimizations along the way.

Select the Phoenix Simulator and open the Grid rollout.

Set the Scene Scale to 1.5 - this will slightly slow down the simulation.

Set the Cell Size to 0.65 and change the X/Y/Z dimensions of the grid such that the painted areas of the chair are included in the bounds of the Simulator box. This will save some simulation time as those empty voxels will not be calculated in vain.

Set the Adaptive Grid option to Smoke, and the Threshold to 0.02.
The Adaptive Grid option allows the container to grow in size once the content of the specified channel near the walls of the simulator reaches the Threshold value. In this case, the container will increase in size when there is smoke near the walls.

Enable the Expand and Don't Shrink option - because fire simulations tend to be turbulent, it is possible that a certain portion of the container will oscillate between being completely empty and filled with smoke/temperature. This could cause the Adaptive Grid option to constantly resize the bounds of the simulation, producing undesirable results (such as sharply cutting off the fire).

Enable Maximum Expansion and set the X/Y/Z dimensions according to your needs. In this tutorial, a Phoenix Plain Force is used to add wind blowing from the left so extra space is provided to the right where the fire is expected to go.

Set the Extra Margin to 5 - this option allows the Adaptation to keep a number of voxels close to the walls as a buffer zone and expand the grid earlier than usual. This can be especially useful when simulating fast-moving objects or explosions as it allows the simulator to expand before any clipping occurs.

Select the Phoenix Fire Source created by the Burning Fuel preset and make sure that the Chair geometry is included in the Emitter Nodes list at the top.

By default, the Emit Mode should be set to Surface Force - this will produce flames only on the surface of the emission geometry.

Set the Outgoing Velocity to 400cm. The Outgoing Velocity parameter controls the strength of the emission. If you'd like the flames to be calm and short, reduce this value accordingly.

Disable Fuel, and enable Smoke and Temperature emission. The Burning Fuel preset we selected earlier sets up a simulation that uses the fuel channel to produce temperature and smoke - this behavior is controlled from the Fuel rollout of the Phoenix Simulator.
However, instead of relying on this, a much simpler and easier to control way to produce fire is to only emit Smoke and Temperature, and to tweak the Shading/Rendering options as necessary. Fuel and burning are better suited for explosive effects.

Set the Particles value to 2.5 - this parameter controls the number of particles (in thousands) born each second. We emit Drag particles to represent the embers produced by the process of burning.
Drag particles are simply Phoenix's version of Particle Advection. As the simulation progresses, the Drag particles are carried (dragged) along by the Velocity channel together with the smoke.

Make sure to enable Export Drag Particle IDs - Phoenix needs the IDs for the Resimulation process. If you want to render with motion blur, you also need to enable output of Drag Particle Velocity from the Source.

Open the Output rollout of the Phoenix Simulator and disable Fuel. As discussed earlier, we don't make use of the Fuel channel so there is no point exporting it.

Enable Grid Velocity export - the Velocity channel is required when doing a Resimulation, and also when rendering the simulation with Motion Blur.

Open the Fuel rollout and deselect Enable Burning.

This option was enabled by the Burning Fuel with Smoke preset we used as a starting point. Since we disabled the emission of fuel, the burning process will not be utilized and keeping this enabled will only consume resources in vain.

Here's how the simulation looks with the higher Outgoing Velocity rate and reduced Cell Size.

Note that we also tweaked the Scene Scale parameter which affects all the dynamics of the Phoenix Simulator.

The fire is still too turbulent and noisy for our purpose so we take care of that next.

Select the Simulator and open the Dynamics rollout.

Set the Time Scale to 0.6. The Time Scale option works as a multiplier for the velocity in the simulation. The lower this value is, the lower the effect of the forces and dynamics parameters such as buoyancy, vorticity, etc. will be.

Reduce the Cooling to 0.1. This parameter will heavily influence the height of the flames in the simulation. Reduce it for taller flames, increase it for shorter ones.

Set the Smoke Dissipation to 0.3. The effect of this change will only be visible in the smoke. You may omit this step in case you plan to only render the fire.

Set all the Vorticity and Randomize parameters to 0 to disable them entirely. For this simulation, we rely on the detail produced by the emission textures and the Buffered Conservation method.

Here's the simulation with Time Scale set to 0.6.

As you can see from the video to the right, the fire is now slightly less turbulent. This is going in the right direction for us.

Here's how things changed after reducing the Cooling to 0.1.

The flames are now longer - as they should be with this type of burning.

Turning off the Vorticity removed the noisiness in the simulation.

In the next step, we add some detail back into the sim by setting the Conservation Method to Buffered.

Still under the Dynamics rollout, in the Conservation section, set the Method to Buffered, with a Quality of 40, and disable Uniform Density.

You may tweak the Steps Per Frame parameter if your setup requires it. For this tutorial, the Steps Per Frame are set to 2. A higher Steps Per Frame value will produce a smoother simulation. This is usually required if the emitter object is moving quickly and producing stepping in the emission, or the outgoing velocity is so high that the fluid becomes noisy. Try to keep this parameter to a value as low as possible because it increases your simulation time linearly, i.e. increasing it twice will increase the simulation time twice.