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The parameters in this rollout control the representation of the fluids in the viewport. All enabled values are drawn if the content is within the specified range.

UI Path: ||Select Fire Smoke Simulator | FireSmokeSim object|| > Modify panel > Preview rollout






Read Cache for Preview | prv_read_cache – Allows to completely disable reading of cache files in order to speed up the viewport and the simulation. When cache files are not read, neither voxels and particles, nor the grid bounding box or the Cache File Content under the Simulation rollout will be shown. This way scrolling the timeline would be quick as there will be no access to hard disk or the network. If you still need to see the grid bounding box and the Cache File Content info, you could leave this option to Always, and instead disable all voxel preview options, the Mesh PreviewGPU Preview and all particle previews. The intended use for this parameter is as a last step performance optimization - once you're done tweaking your setup and you're ready to commit to a high-resolution, overnight simulation, disable the preview of cache files.

Always – Cache files are always read by the preview.
Disable During Sim
 – Cache files are read only when the simulation is stopped. This would speed up the simulation and is good for overnight simulations where you don't need to watch the simulation constantly.
Don't Preview Caches
 – Cache files are never read for the preview. They will only be read during rendering, or in case any of the Phoenix tools requires them - e.g. the Particle Shader, the Grid Texture, etc. 

Detail Reduction | gpudown – Decreases the grid and particle detail in the preview. A value of 0 means no reduction. Increase this value if the interface starts to lag due to the simulation being very large. This parameter controls both the viewport preview and the GPU preview.

Auto Reduction | prv_autoreduct – Enables automatic adjustment of the Detail Reduction parameter. The preview detail will be reduced up to a point where the preview will display fast without blocking the interface. Note that the detail will only decrease automatically, but will not increase.

Show Mesh | show mesh – When enabled, shows the Isosurface as a mesh. The Isosurface  is defined in the Surface section of the Rendering rollout. This mode overrides the Voxel Preview mode. Note that if Mode is set to Ocean Mesh in the FireSmoke Rendering settings, the surface is generated in the viewport with low mesh resolution in order not to slow down the user interface significantly.


Voxel Preview

Phoenix FD can only preview the channels present in the cache file for the current frame. To see the list of available channels and their ranges, go to the Cache File Content section of the Simulation roll-out.

Only if selected | show_only_sel – When enabled, the viewport preview is only drawn if the simulator is selected.

Active view only | prv_avonly – When enabled, only the selected viewport shows the content of the simulator.

Show box | showgrid – Shows the bounding box of the simulator. The green outline is drawn based on the settings in the Grid roll-out while the red outline displays the bounds of the currently loaded cache file.

Graph cells | gridcells – Shows a lattice with the cell sizes on the sides of the simulator's box when there is a loaded cache file.

Only the overlap of | prv_and – When enabled, shows only the cells where the following selected channels overlap.

Temperature | prv_temperatureprv_t_threshold, prv_t_threshold2, prv_t_color, prv_t_color2 – Enables the representation of the temperature.
As fire
| prv_plank_t – When enabled, the natural color of a hot black body is used for coloring the temperature. Otherwise, the color ramp is used.
| prv_smoke, prv_smoke_threshold, prv_smoke_threshold2, prv_smoke_color, prv_smoke_color2  – Enables the representation of the smoke.
| prv_fuel, prv_fuel_threshold, prv_fuel_threshold2, prv_fuel_color, prv_fuel_color2 – Enables the representation of the fuel.
| prv_velocity, prv_v_threshold, prv_v_threshold2, prv_v_color, prv_v_color2 – Enables the representation of the velocity.
Forces | prv_forcesprv_f_thresholdprv_f_threshold2prv_f_colorprv_f_color2, prv_force_list – Enables preview of how Phoenix forces or standard 3ds Max forces will affect the simulation.
RGB | prv_uvw, prv_uvw_threshold, prv_uvw_threshold2 – Enables the representation of the RGB channel.

Auto Range | prv_autorange – When enabled, automatically adjusts the preview ranges of visible channels for the current frame so that important data is always visible and the preview is always quick.

Draw Just a Slice | prv_sect – Only a voxel-thick cross-section of the grid is visible in this mode. This allows for a better view of occluded details and can help when previewing very rich data such as velocity fields.

Along Axis | prv_sect_axis – Specifies the axis along which the grid will be sliced.

Slice Level | prv_sect_lvl – Specifies the offset of the slice from the bottom center of the grid, in voxels

Using the Add or Remove buttons will allow you to select which forces will be previewed. Note that the force preview is exclusive with all other voxel channel previews and will override other voxel channels. Unlike other voxel preview channels which use the size of the loaded cache, the Forces preview can also work without a loaded cache and will use the grid size of the Simulator.

Additionally, some Phoenix FD and standard 3ds Max forces require the previous velocity at their acting position in the grid. This is not yet supported by the Forces preview. As a result, forces such as the Drag force are shown as if their velocity is always 0 and will not be visible. In addition, forces that act differently depending on the quantity of content in the grid (e.g. amount of liquid, smoke, or no content) are not yet supported by the preview.

Particle Preview


Particle Previewprv_particles, prv_prt_name – Enables the preview of particles. The controls below affect the visualization of the currently selected particle group.

Show | show_prt_face – Enable the preview of the currently selected particle group in the viewport.

Particle color | prv_prt_color_face – Specifies the color of the particles when standing still. Moving particles are displayed as a color between this color and white, depending on their speed. The faster the particles, the whiter they will appear. Note that if the particle system has a RGB channel exported, it will be used instead of the Particle color. (The preview will still be affected by the White speed if the particle system has a Velocity channel.)

Auto White Speed | prv_prt_awspeed_face – When enabled, automatically calculates the preview White Speed based on the particle velocity.

White Speed | prv_prt_wspeed_face – When Auto White Speed is disabled, allows you to specify the speed at which the particle preview color becomes pure white.

Draw Just a Slice


Draw Just a Slice | prv_sect – When enabled, only a voxel-thick cross-section of the grid is visible. This allows for a better view of occluded details and can help when previewing very rich data such as velocity fields.

Along Axis | prv_sect_axis – Specifies the axis along which the grid will be sliced.

Slice Level | prv_sect_lvl – Specifies the offset of the slice from the bottom center of the grid in voxels.



GPU Preview


The Phoenix GPU Preview shows the shading of the simulator using the current Volumetric Options. The preview works in real time and you should use it to quickly preview how changing volumetric options and curves affects the look of the simulation. Additionally, it can automatically save images during simulation, so you can easily preview it in motion. Note that the GPU preview is not a replacement for rendering though - in order to display quickly, it ignores Displacement, ignores any volumetric texture mapping of the Fire or Smoke, and all lights are treated as directional, so using dome lights, area lights or global illumination would produce different results than the preview. If you need to iterate on the final look of the simulation in complex lighting setups, V-Ray GPU IPR would allow you to get a much closer result to rendering.

GPU Preview as 3ds Max Extended Viewport



Here is how the GPU Preview looks next to the voxel preview of a Phoenix Simulator:



In 3ds Max 2015 and later, the real-time GPU preview of fire and smoke can be directly shown inside the viewport next to all other objects by just turning on the Enable In Viewport option.

Alternatively, GPU preview can also be enabled in an extended viewport. The Phoenix FD GPU Preview extended viewport shows only the selected simulator node and uses the parameters of the selected viewport. To enable it, right-click the viewport type and select Extended Viewports > PhoenixFD GPU Preview:




Enable In Viewport | gpu_viewport – [3ds Max 2015 and later] When enabled, the GPU preview can be directly seen inside the viewports together with all other scene objects and there is no need to create a dedicated viewport. Note that geometries that intersect the Simulator box or are inside the simulator might appear completely behind the entire fluid or in front of it. Another limitation of the viewport preview is that it won't be visible if the camera goes inside the Simulator.

Background color | prv_gpu_color  – Specifies the background color.

Gamma | gpu_gamma – Specifies the gamma for the GPU preview. When Enable In Viewport is turned on, this parameter is ignored and the 3ds Max gamma setting is used.

Lighting | gpu_lighting, gpu_lightnodes – Enables the lighting via an Include/Exclude list of light sources. Without lighting, the smoke will not be visible and only fire will be rendered.

Exclude... | Launches the GPU Preview Light Include/Exclude List window which can be used to specify which light sources will be used for lighting.

Ambient light | gpu_ambient – When Lighting is enabled, this parameter specifies the color of the ambient light. 

Self-Illuminate... – Calculates the illumination that the fire throws onto the smoke and show it in the GPU preview. The effect is the same as using Grid-based self-shadowing in production rendering. However, it does not use grid reduction so it will be calculated with the full grid resolution, which might take longer than using grid reduction. The self-illumination will be visible in the GPU preview viewport until the frame is changed.

Save images during sim | gpu_save – When enabled, automatically saves the preview of each newly simulated frame as a .png file in the same folder as the simulation result.

Export alpha (premultiplied) | gpu_alpha – When enabled, the .png file contains an alpha channel that can be used for compositing. Note that the color is already multiplied by the alpha.

Save – Renders a whole sequence from the already existing simulation into a series of .png images in the same folder as the simulation result. The From and To values specify the frame interval for the sequence, and the animation controls from the Input panel will apply (play speed, looping, etc).

In order to get proper shading for the smoke, the light source has to have shadows enabled, including atmospheric shadows. Otherwise, the smoke will be rendered as flat and featureless.

V-Ray lights have these settings enabled by default.

A 3ds Max light, such as an Omni light, must have its Shadows On, Shadow type set to VRayShadow (or Ray Traced Shadows if using the default Scanline renderer), and Atmosphere Shadows On.