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Set the Time Configuration → Animation Length to 120 so that the Timeline goes from 0 to 120.

When the cardboard burns, the paper disintegrates into ashes during the burning process. Therefore we need enough details in the geometry for making realistic ashes. We start with very simple box geometry, a box without any segments. Size is 70 X 111 X 37 cm. Then, we convert it into NURBS.

With the NURBS box selected, go to the Modifier panel, in the Surface Approximation rollout and set the Edge to 2.0. Then click on Advanced Parameters and enable the Delaunay option. This creates random edges over the surface of the box. The Delaunay triangulation topology is also suitable for cloth or softbody type of simulation. For the flying paper pieces, we are going to simulate the softbody with BulletPhysics in thinkingParticles.

Convert the NURBS to Editable Poly geometry.

With the editable poly mesh selected, go to the Modifier panel, randomly select a small patch of the faces and detach them. Repeat the process until all faces are detached into small patches.

Duplicate the box that we have created in the previous step few times, and pile them up as the image shows. In this example, we made ten copies. Rename them to Box001 ~ Box010.

As this tutorial is about thinkingParticles working with Phoenix, the focus is not on how the dynamic sets were done. However, below is an outline of some critical dynamic sets.

• Four box geometries (Box001 ~ 004) are taken into thinkingParticles through Obj. To Particle operator. Then those boxes are hidden in the scene.

• The boxes then are activated by two omni lights (Omni001 and Omni002) in the scene (through fragment operator). The omni lights are animated to control part of the boxes to start burning.

• The activated fragments then divide into two groups: Group A and Group B.

• Then the paper fragment - Group A breaks into smaller debris called SMALL_DEBRIS.

• Then the smaller debris is subjected to the Wind force in the scene. The turbulence from the Wind pushes the smaller debris and gives them some random motion.

With the thinkingParticles node (Thinking001) selected, go to Modifier Panel and press the Properties button.

Right-click on Master Dynamics and select Cache Record.

After cache generation is finished, a green arrow appears on the left of Master Dynamic.

Go to Create Panel → Lights → VRay and press the VRayLight button. Click and drag to create a VRay Light and place it anywhere in the scene.

With VRayLight selected, go to the Modifier panel. Set type to Dome.

Decrease the Multiplier to a value of 0.1.

In the Options rollout, check the Invisible option.

You can put a VRayHDRI texture in the Dome Map slot. Feel free to use an HDRI map of your choice. Decrease the Multiplier to a value of 0.05.

With PHXSource001 selected in the Modifier panel, press the Add button in the PHXSource and select thinkingParticles node (Thinking001, pointed by the white arrow) in the scene.

Phoenix automatically generates a list of particle sets in your scene. Pick up the Particles Group_A, Group_B and SMALL_DEBRIS of Thinking001 and press OK. Those are the particle groups we want to emit fluid.

At the bottom of PHXSource, Prt Shape is set to Use Particle shape. This means Phoenix can read shape data from thinkingParticles.

Go to Create Panel → PhoenixFD, press the FireSmokeSim button, and then click and drag a Fire/Smoke Simulator into the scene.

Set the volume of the Grid as shown in the example. The grid is shown in purple color. Set its x, y, z respectivelyto 48, 157, 79, the Scene Scale to 1.0, and Cell size to 1.0 cm. Enable Adaptive Grid (based on Smoke) and set Extra Margin to 5, so the grid would be able to expand and accommodate the growing smoke. Also, enable the Maximum Expansion option and set the values as shown (parameters are circled in white, in the viewport the grid is in red color). Adaptive Grid allows you to save memory and simulation time as the simulation grid is not set to its largest extents at the very beginning and expands gradually.

The exact position of the Simulator in the scene is [ 44, -41, 96 ].

Leave all parameters in the Dynamics rollout to their defaults.

In the Preview rollout, enable the GPU Preivew option, so that we can preview the smoke shading directly into the viewport.

Once the simulation is completed, you can make a preview animation. These are our first results. As you can see, there is not much detail in the fire, and the smoke seems too thick. Let's see how to correct it.

Or you can simply load up a Rendering Preset from a *. tpr file that is provided in the sample scene.

Render again. Now the fire looks brighter, and the amount of smoke is adequate.

Simulate again. As you can see, with Time Scale set to 0.7, the fire became slower.

Make a test rendering. Now the fire appears unrealistic, because at its root it is too solid. Let's address that.

Go to Fire/Smoke Simulator → Rendering rollout, Volumetric Option. In the Fire rollout, put a VRayDistanceTex in the Texture slot. Enable the Modulate option. In the VRayDistanceTex, add Group_A, Group_B and SMALL_DEBRIS in the list.

The VRayDistanceTex is a V-Ray specific procedural texture that returns a different color based on a point's distance from an object(s) specified in a selection list. We can use this texture as a mask to modulate the fire opacity.

Make a test render now with VRayDistance in the modulate slot. The fire looks more realistic.

Now that the simulation looks good, check the Stop Frame Timeline option so that it simulates from frame 12 to 120. Press the Start button to the simulation of the whole animation.

Go to Select by Name, select the Particles BOXES of Thinking001 in the list.

With the Particles BOXES of Thinking001 selected, right-click and choose Chaos Phoenix Properties. Check the Solid Object option. This option can assure that the fluid collides with BOXES group instead of penetrating them.

To compensate for the problem, we increase the value of Outgoing Velocity of the PHXSource to a value of 200.0. 

Also there is no clipping issue between the fire and the boxes. So we are all set for the fluid simulation, ready to enter the next stage.

The box material is basically two materials mixed together: (1)Burned Box material and (2)Unburned Box material. The blending mask is a VRayDistanceTex that uses two geospheres to generate black and white mask texture. On top of the V-Ray Blend Material, we add V-Ray Bump Material to give the boxes round-edge look during render time.

Let's start with a VRayBlendMtl connected to the Base material and then in the first Coat material slot plug in a VRay Material. Rename them to Burned-Box and Unburned_Box respectively.

For the Burned-Box material, put Box_diffuse.jpg in the Diffuse slot. Set the Diffuse Color to RGB of (11, 2, 1).

For the Burned-Box material, reduce the diffuse value from 100.0 to 5.0. The combination of bitmap and diffuse color makes the texture darker, as it was burned.

For the Burned-Box material, plug in a VRayDistanceTex in the Displace slot. Set the Displacement value to 15.0.

For the VRayDistanceTex, put a Noise texture in the distance slot, to randomize the distance. By doing so, we will have a more organic looking mask. For Noise texture, set the type to Fractal. Size set to 15.0.

To invert the VRayDistanceTex, we add a Color Correction on top of that. Set its channel to Invert.

At this point, if we apply the texture map to the Diffuse Color of a default V-Ray Material, we should get something like the image on the right. This texture is ready for Burned Box displacement map.

For the mask, we are blending the Burned and Unburned materials, using a VRayDistanceTex. In the texture, add two GeoSpheres in the VRayDistanceTex Objects list. Add a Noise texture in the distance slot. Set the Noise Type to Fractal, Size to 15.0, Levels to 5.0.

The image shows the rendering with V-Ray Bump material applied. Notice the subtle rounded edge in the boxes.

This image displays an overview of the complete Burning Paper Material. Because the burning paper emits light, we choose VRayLightMtl to start with. Then we put in a procedural texture in the Light color.

In the VRayCompTex, put a Gradient Ramp in Source A. Put a Noise texture in Source B. Set Operator to Multiply (A*B).

To show you what this complete VRayLightMtl looks like, we applied the material to a simple plane. It is an orange-yellow electric pattern. When the material is ready, apply it to the SMALL_DEBRIS.