Page History

Here's how the simulation looks so far. There are a few things to address:

1. The smoke is going straight up instead of twisting the way a dust devil would. We resolve this first by adding a 3ds Max Vortex force and tweaking its settings.
2. The smoke emission is too symmetric and produces a mushroom - we resolve this by modulating the emission with a Gradient texture.
3. The entire poly plane is emitting smoke instead of only the top faces - this can be resolved by assigning the top faces a unique Polygon ID and specifying that in the Phoenix Source.

If you were to run the simulation now, you'd notice that the Vortex force has a minor impact on the simulation.

Note the vertical speed of the smoke - this is caused by the high temperature coming into the simulation from the Phoenix Source.

This, coupled with a high Smoke Buoyancy value, forces the smoke upwards and partially negates the effect of the Vortex force.

Here's how the simulation looks now:.

The smoke is still too dense and produces a mushroom at the top.

We address this next by tweaking the Phoenix Source and the emission geometry.

Select the Phoenix Source and set the Polygon ID parameter at the bottom to 2.

Set the Noise parameter to 2 - this will break-up the emission by modulating the Outgoing Velocity.

Reduce Increase the Outgoing Velocity to 500 or so so a greater amount of smoke is emitted into the simulation.

Increase the Smoke parameter to 2 - this will cause the emitter to produce thicker smoke.

Note that those parameters are simply an artistic choice and in no way set it stone - you may tweak them as you see fit.

Here's how things are looking:.

The mushroom is no longer there but we still need to address the sharp edges produced by the profile of the emission geometry.

We can do that by using a Radial texture as the Outgoing Velocity mask for the Phoenix Source.

The funnel is now starting to take shape.

We are now ready to start tweaking the Phoenix Simulator properties.

Select the Phoenix Simulator and open the Grid rollout.

Set the Boundary Conditions: Z to Jammed (-). This will cause the bottom wall of the simulator to act as a solid obstacle, allowing us to use it as the ground.

Set the Cell Size to 8 to increase the resolution of the grid.

Set the X/Y/ Z size to 80/80/20.

The Adaptive Grid option should be set to Smoke by the Large Scale Smoke Preset. The Adaptive Grid allows the container to resize on-demand as the simulation progresses, saving you a lot of time. Instead of calculating a giant grid from the start, a specific channel is tracked (Smoke in this case) and the grid is automatically resized around it.

Enable Maximum Expansion and set the X/Y/Z dimensions according to your needs. Because the Z axis is Jammed in the negative Z direction, the Z(-) field is left at 0. 

Set the Extra Margin to 10 - 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. 

occurs. 

Here's how the simulation looks with those tweaks:.

The motion of the funnel is interesting enough, and it seems to be forming properly.

However, the simulation feels static. In real life, a dust devil forms spontaneously and chaotically moves all over the place. Our funnel, on the other hand, is simply sitting there and rotating.

In the next step, we will make the simulation more dynamics by animating the position of the Vortex field, and adding a Noise modifier to the emission poly plane geometry.

Create a Helpers → Phoenix FD → PHXTurbulence.

If you are working with Phoenix 4.41 or later, set Set the Turbulence Strength to 40.

If you are using an earlier version prior to Phoenix 4.41, you can set the Turbulence Strength to 250.

Next, no matter which supported version of Phoenix you are usingNext, set the Turbulence Size to 900 and Fractal Depth to 5.

The Strength is self-explanatory - the higher the strength, the stronger the effect of the turbulence force on the simulation.

The Size is increased to 900 to get large-scale swirls. You can compare this to the Simulator size in the Grid rollout. The Fractal Depth works like a layering option. A fractal depth of one will give you a single noise layer. A fractal depth of two will give you 2 layers - the first with whichever Strength value you used and a Size of 900, and a second one multiplied on top with half the Strength and Size of the previous. In other words, the higher the Fractal Depth is, the more layers there are in the noise, and the more detail there is.

You may preview the Turbulence by including it in the Preview → Forces Preview Set. Don't forget to disable the GPU Preview because it overrides the Voxel Preview and the Forces won't show up in the Viewport.

Image RemovedImage Added

A V-Ray Sun and a V-Ray Physical Camera are used for rendering the effect.

The Sun Filter Color is set to White, with the Mode set to Override.

The Sun and Sun Target positions are as follows:

• Sun XYZ: [ -14901500, 366365, 2180 ]
• Sun Target XYZ: [ 130, 20, 0 ]

The Camera and Camera Target positions are:

• Camera XYZ: [ -2310, -33403350, 553 640 ]
• Camera Target XYZ: [ -300, -40, 620 640 ]

Set Simulator → Dynamics → Steps per Per Frame to 1 so you don't lose detail in the re-simulation process. If you're following along the tutorial, it should already be set to 1.

In general it's not recommended to change any Dynamics settings between the original simulation and Time-Bend Resimulation because all of them will affect the resimulation.

In order to get the closest match, both the original and resimulation should be run with 1 Step per Frame.