The FumeFX Grid
The heart of FumeFX resides within its simulation engine. This entire, quite sophisticated system is built around a very simple object called the FumeFX Grid. You can think of the FumeFX grid as a 3-dimensional representation of a volume in which the simulation of smoke and fire will take place. Whatever size volume you define when you drag out the FumeFX grid will act as a set of boundaries for the simulation.
In order to create a FumeFX grid in your scene, simply go to the Create Command Panel and from the Geometry dropdown menu, select FumeFX -> FumeFX.
Once selected, like any other object inside of 3ds Max, simply drag out the new volume in any viewport. When done, you'll get a yellow rectangular wireframe box like the one shown below.
The FumeFX Grid
Note: Unless you’re using “Boundless” grid options, no simulation will take place outside of this volume.
Since FumeFX is based on real-world computational fluid dynamics, something to consider is the scale of your scene. Just like other simulation engines, you will get unpredictable results if your scenes are microscopic or gigantic in scale. Imagine a matchstick simulation where the geometry is over a mile long in real-world unit - the precision and accuracy of the simulation would not be to the correct scale of the desired result, so be sure to watch the scale of your scenes.
It is important to realize that within the Grid is a set of voxels (Volumetric Pixels), and the density of this volume can be manipulated to get higher or lower precision within the same space. The volume within the FumeFX container is automatically sub-divided into a set of equal sized rectangular "cells", stacked on top of one another, and each one is designed to contain data pertaining to the simulation within them. Since artists are visual by nature, users can visualize this grid at any time to get a better idea of how much detail their simulation will have.
FumeFX Volume Grid display (lower resolution)
FumeFX Volume Grid display (higher resolution)
Note: It is important to remember that the higher the detail within the volume, the longer the amount of time it will take to run the simulation and the larger the amount of storage it will require. See the System Requirement explanation in the Overview to help you determine your storage requirements.
Once you've gotten your FumeFX Grid placed within your 3ds Max viewports, it’s time to go to the Modify Command Panel.
With the FumeFX Grid selected, you'll be presented with the controls and rollouts necessary to access the power within FumeFX and also serves as a starting point for your interaction with FumeFX. It contains two rollouts: General Parameters and Viewport. From these rollouts you can access other parts of the interface, edit your preferences, modify parameters of the FumeFX Grid, or control the way that your simulation appears in the 3ds Max viewports.
General Parameters Rollout
The General Parameters rollout contains the parameters of your simulation area and the overall grid size. This group of controls is also available in the Floater Window; one difference is that in the Modify panel, this rollout also includes the main toolbar – your gateway to other parts of the interface.
Icon Toolbar
This group of controls lets you quickly access the basic set of FumeFX dialogs and information.
Preview - Selecting this button opens the output Preview Window. You can open the Preview Window at any time from this toolbar, the FumeFX Floater, or the FumeFX Status Window. If you open it during simulation you may have to wait until the current frame is calculated for the window to refresh.
FumeFX UI/Floater - This button opens the main part of the FumeFX user interface – the FumeFX UI floating window.
Preferences - This button opens the Preferences dialog box, which lets you quickly configure local or global parameters.
About FumeFX - Selecting this icon opens a dialog box that displays your FumeFX version and plug-in ID. Inside this dialog you can also reauthorize the FumeFX or mental ray shader plug-in.
Simulation Area
In this rollout you will also find a group of controls for FumeFX grid dimensions and detail. You can also access these controls under the General tab of the FumeFX UI floating dialog.
Spacing - This parameter directly affects the detail level in your simulation. Type in or use the spinner to set the spacing of the voxel-based grid. The chosen value defines voxel size; smaller voxel size allows for more voxels in simulation, which produces greater detail.
Width, Length, Height - These three values set the volumetric dimensions of the FumeFX Grid, thereby establishing the boundaries for simulation within the scene.
Adaptive - While enabled, the grid will expand and shrink with the movement or absence of fluid to use only the necessary portion of the overall grid space. It is highly recommended to leave this enabled because it reduces simulation time and file size.
Sensitivity - When the Adaptive option is enabled, this parameter defines the boundary’s sensitivity to the production of smoke/fuel/fire. The larger the number, the tighter the adaptive box will be. Leave this value between 0.1 and 0.01.
Note: If there is a source that does not emit any matter, but just produces wind and you want FumeFX to enlarge grid accordingly to the wind strength, set the Sensitivity value to zero.
Simulation Loop - It is convenient that the simulation loops through the simulation range while you're tuning simulation parameters. This way you can focus on initial parameters setup without the need to re-click on the simulation button.
Save Caches - While you're looping simulation and tweaking parameters on a low resolution grid, it might be handy that you do not save any caches to gain a bit more speed.
Reset on Loop – When loop reaches the end of the simulation range, the simulation grid will be reset.
Viewport Rollout
By default, your simulation will not appear in the 3ds Max viewports. The FumeFX Preview Window is intended to give you the most accurate representation of what your simulation will look like after rendering. However, for scene layout purposes, it is sometimes helpful to view the simulation in the viewports. In the Viewport rollout, you can enable and adjust this viewport display.
Enable Display - The large Enable Display button toggles the viewport display on or off. Next to this, there is a small checkbox marked with a plus sign. If this button is selected, FumeFX will continue displaying its data in the viewport even if the FumeFX object is not selected. You need to have both buttons enabled when doing a 3ds max viewport preview. Since FumeFX requires loading of output files in order to display its data, it could take some time before viewport updates.
Display Optimize
Reduce - Use the spinner to set the level of detail; the viewport will display every nth voxel across all 3 axes.
Threshold Scale - This value acts as a multiplier for the individual threshold values of each channel. For each channel, the corresponding threshold spinner sets the minimum value that will be displayed, in FumeFX units (Smoke, Fire and Fuel), or world units (Velocities and Forces).
Channel/Threshold
In FumeFX, you are able to select which channels are exported to the output file for rendering. This group of controls will let you mix varying intensities of these channels in the viewport display. Of course, channels that are not present in the output file cannot be displayed in the viewport. If a simulation is in progress, only the channels used in the simulation can be displayed.
Select the Channels that you want to display. Then, adjust the corresponding Threshold spinners to set the minimum values for display.
Fuel - Shows unburned Fuel.
Oxygen – Shows unburnt oxygen inside the FumeFX grid.
Velocities - Shows Velocities in the grid. In order to view velocities, they must be exported first. Interpolation between two colors is done based on the Hue.
Forces - Shows Forces (in case FumeFX is bound to any).
Turbulence - Shows Turbulence as created through the Simulation controls.
Temperature - For the display of temperature you can set Min. and Max. values with a linear 2-color gradient in between. Interpolation between two colors is done based on the Hue
Objects/Sources – Shows voxels that are occupied by the collision object or source.
Effector – This option enables you to visualize the strength of Effector(s). It is possible to visualize them after simulation is done as Effector usually requires channels like Smoke, Temperature, etc. to be present in the grid. To be able to visualize Effector that uses Velocity channel as in input, you will have to export velocities. If you want to see the effect strength of more than one effector, you need to list all thse names separated by the comma sign (for example: eff1,eff2,smokeEff,testEff).
Illum – Displays shadows inside the viewport. Higher value means better quality.
Scale Multiplier
The Force and Velocity vectors can be scaled for an exaggerated or disparaged display.
Show Slice
Show Slice - If you enable this checkbox, you can view the fluid values on an intersection of the grid with a specified 2D plane. To do this, select from three axes pairs in local space (XY, YZ, or XZ); then, adjust the Position and Thickness spinners to determine the exact location shown.
Position - Once the Show Slice checkbox is on and a slice plane is set, use this spinner to move the slice plane along the FumeFX Grid volume to see the voxels within the grid.
Thickness - Once the Show Slice checkbox is on and a slice plane is set, use this spinner to determine how many cells within the volume are shown as part of the current slice.
Grid - Selecting this will show a voxel grid on the slice and turn off the FumeFX grid display on the sides.
Numerical Values - This option will write out the contents of each voxel cell with 2-digit precision. This can be handy when you want to see what cells within your simulation contain and the values associated with the voxels.
Voxel Grid
Checking this option enables you to see the dimensions of voxels used in the simulation; these dimensions can be projected to one or more sides of the grid.
None - No grid is shown.
XY plane - Shows the grid on the bottom of the FumeFX simulation.
Automatic - Shows the grid on all sides that appear "inside" the current view.