--- title: "Liquid Preview" canonical: "https://documentation.chaos.com/space/PHX4MAYA/125736916/Liquid%20Preview" format: markdown --- ## **Overview** --- The parameters in this rollout control the representation of the fluid’s caches in the viewport, showing a preview of what the fluid is doing. These preview controls can give you a sense of what is going on with your simulation, and whether it needs tweaking, before you decide to start rendering. > Macro (ui-text-box) > > The **Viewport Preview** is almost completely independent from rendering, and allows you to control the visibility of specific **Grid Channels** and** Particle Types**, in order to customize the preview. Depending on the **Read Cache for Preview **mode used, all enabled parameters in this rollout will be displayed in the viewport, provided that the cache file’s content is within a parameter’s specified value range for that frame. Liquid simulations are displayed using the **Particle Preview** by default. You can also enable the **Show Mesh** mode, to override the Particle Preview and show the liquid as a mesh. The Particle Preview section lets you control the visibility of different Particle Types, and manage their preview color. For example, you could preview only the Splash and Foam particles. There is also a **Voxel Preview**, which uses 2D triangles to emulate the shape of the volume. You can choose to preview specific Grid Channels, such as Viscosity and RGB, or even preview the Liquid Channel as voxels if you plan to render the liquid particles using a volumetric render mode, for example. In addition, you can preview the simulation’s Velocity, to see how Phoenix forces or standard 3ds Max forces affect the simulation. > Macro (ui-text-box) > > Keep in mind that the Voxel and Particle preview parameters are all independent from rendering. They do not affect the render settings. > Macro (ui-text-box) > > UI Path: ||Select [PhoenixFDSim](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125765148)|| > Attribute Editor > Preview rollout ## **Parameters** --- ![image](media://9a60ebb6-0644-4d13-9cc3-59039e601632) **Read Cache for Preview **| *prvReadCache *– 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](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125701902) 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 Preview**, **GPU 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](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125830144), the [Grid Texture](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125731978), etc.  **Detail Reduction** | *detailReduction* – 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. Note that this parameter does not affect the Mesh preview. **Auto Reduction** | *viewAutoReduction* – Enables automatic adjustment of the** Detail Reduction** parameter to improve display performance. 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. This option works only for the Voxel and Particle previews. **Only if Selected** | *onlyIfSelected* – When enabled, the content in the viewports is only shown for the selected Simulators. **Active View Only** | *activeViewOnly* – When enabled, only the selected viewport shows the content of the Simulator. **Show Box** | *showGrid* – When enabled, displays the Simulator's box in the viewport. The Simulator box settings can be modified from the [Grid rollout](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125995969). **Graph Cells** | *showGridCells* – Shows a lattice with the cell sizes on the sides of the Simulator's box or the Slice Preview. ### **Mesh Preview** --- ### Particle Preview --- > Macro (ui-text-box) > > The parameters here control the visualization of **Particle Types** generated by the Simulator. Phoenix can only preview the Particle Types present in the cache file for the current frame. > Macro (ui-text-box) > > You can specify a** Particle Channel **to use as a basis for adjusting the particle preview color, using the **Scale Color By** option. For example, you could set the Scale Color By option to the Speed particle channel, so that the faster the particles move, the whiter they appear in the preview. > > You can find more info on Particle Channels from the [Particle Channel Ranges](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125732062) page. ### **Voxel Preview** --- > Macro (ui-text-box) > > The **Voxel Preview** displays the **Grid Channel** content of each cell. Phoenix can only preview the channels present in the cache file for the current frame. All enabled channels are drawn if their content is between the corresponding thresholds. > > To see the list of available channels and their ranges for an input sim cache, go to the Cache File Content section of the [Liquid Simulation](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125701902) rollout. You can also find more info on the [Grid Channel Ranges](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125895763) page. > Macro (ui-text-box) > > Note that you can also specify the Voxel Preview value range for any Grid Channel, if you disable the **Auto Range** option. > > For example, you could enable only **Visosity**, and specify the range to be between 0.7 and 1.0, so that you can see where the liquid is getting more viscous. Grid Viscosity Channel values that are below 0.7, or above 1.0, would not appear in the preview at all. ### Bake Streamlines --- ### Slice Preview --- > Macro (ui-text-box) > > The Slice preview displays only a single slice of voxels which can be convenient for debugging and fine-tuning a simulation.