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TimeBendControls
TimeBendControls

Mode | animmode – Chooses between different options for animation control:

Linear – This is the default mode. The cache sequence is played with a constant speed and can be offset forward or backward on the timeline, as well as sped up or slowed down.
Cache Index – The Direct Cache Index specifies which cache file will be loaded for the current timeline frame. Can be used to either show a static simulation, or the Direct Cache Index can be animated in case you want varying play speed, including playing the simulation backwards.
Loop – A specified piece of the simulated sequence is looped. Can be used for flowing and repeated effects such as fireplaces, campfires or torch fires, water in fountains, waterfalls or boiling liquid. In this mode, the Cache Origin parameter specifies the beginning of the looped sequence, the Length parameter specifies the length of the loop, and Loop Overlap specifies the number of overlapped frames that ensure smooth transition between the end and the start of the loop. Note that you need to have simulated at least Cache Origin + Length + Loop Overlap cached frames for this mode to work correctly. When looping particles, make sure to export the particle ID channel in the Output rollout.

Direct Cache Index | t2f – Used in Cache Index mode, specifies the cache file index for the current timeline frame. Can be animated in order to achieve more interesting time-bend effects.

Timeline Origin | playat – An offset specifying which timeline frame the starting cache will be placed on. You can think of it this way: "Put cache #(Cache Origin) on timeline frame #(Timeline Origin)".

Cache Origin | inpoffset – An offset specifying which cache file from the sequence will be placed on the timeline at frame Timeline Origin. You can think of it this way: "Put cache #(Cache Origin) on timeline frame #(Timeline Origin)".

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PlaySpeed
PlaySpeed
Play Speed | play_speed  – A multiplier for the playback speed. Value of 1 means that each timeline frame corresponds exactly to one cache file index. If the play speed is not exactly 1.0, frames will be blended between by using the method specified by the Grid Blend parameter. If you want to blend particles, you must have exported their ID channel during simulation (this can be done from the PHX Source or Foam/Splash rollouts, depending on the way you create your particles). Note that Play Speed is not keyable - you should switch to Cache Index mode and animate the Direct Cache Index.

Play Length | inplength – The duration in timeline frames. In Linear mode, when this parameter is larger than 0, the sequence length is limited to its value. In Loop mode this parameter shows the loop length. 

Loop Overlap | loopjnt – In Loop mode, specifies the number of timeline frames after the loop's end that will be blended with the loop's beginning to make for a smooth transition. Keep in mind that the end transition frames are not in front of the sequence end, but after it. For example if the loop starts at frame 35 and has a Length of 20 and a Loop Overlap of 5, the transition frames will start at frame 55 and will end at frame 59, which means the simulation must be at least 59 frames long. It is recommended that the Loop Overlap value be longer than the average "lifetime" of the simulation elements while involved in highly visible motion. For example, for a waterfall, the Loop Overlap value should be at least the average time it takes for a water droplet to fall the full distance before being absorbed into the water at the bottom. For a campfire, it should be at least the average time for a particle to rise up and disappear/die. Correct setting of this value is especially important for simulations that contain particles.

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FrmBlend
FrmBlend
Grid Blend | frmblend  – Used for grids when the Play Speed parameter is not exactly 1.0, or the Direct Cache Index for the current timeline frame is fractional, or you have specified a Loop Overlap in Loop mode. In these cases, a single timeline frame must be constructed from two cache files by blending between them. Each time the timeline is scrolled to a new frame, the caches for this frame will be blended again. You can choose between three different methods for blending between grids from cache files. Note that particles are blended using a much simpler method and Grid Blend does not affect them:

Interpolation – Simple linear interpolation suitable for slow simulations. This is the fastest method but it does not capture movement well and may produce flickering.
Velocity – Velocity-based interpolation. Produces better results, but works more slowly. Captures well the movement of the fronts of the plumes, but does not work well for smoke moving backwards, and also may produce flickering. It  requires an exported grid velocity channel from the Output rollout.
Precise Tracing - Improved Velocity based interpolation for Fire and Smoke simulations. Captures fire/smoke plume movement very well and can handle very low Play Speeds. Requires an exported grid Velocity channel, as well as Advection Origin channel from the Output rollout.

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Frame Blending is better suited for simulations without much variety in velocity. For more chaotic simulations, it is better to run a Resimulation using Time Bend controls. Time Bend Resimulation will calculate a better intermediate result for each frame and store it in new cache files that can later be loaded faster, as opposed to Frame Blending which re-launches every time the timeline frame changes. However, for very slow moving simulation the Precise Tracing method produces better looking results than Time Bend Resimulation. For more information, see How to slow down a simulation, animate the time-scale, etc.

Load Nearest If Missing | loadnearest  – If there is no cache file at the required frame, the nearest cache is found and loaded. This is useful for a simulation that ends with a sequence of static frames (for example, still liquid or freezing fire) as it prevents the need to render multiple identical frames after movement has stopped.

Flip Up Axis | ifyz – When enabled, flips the Y and Z axis of the cache's transformation. This is useful when the cache was created with a different up axis (for example in Maya).

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Example: Timeline Origin

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The following example demonstrates how the Timeline Origin parameter can be used to specify which frame on the timeline is treated as the first frame when reading the Input Path cache files.

The files go from simulationFrame_000 to simulationFrame_030. When the Timeline Origin is set to 10, they are read as if they were saved as simulationFrame_010 to simulationFrame_040.

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Channel  | sm_ch – Controls which channel is affected by changes made to the settings below. The following channels can be smoothed:

Liquid
Smoke
RGB
Fuel
Velocity 

Smooth this channel | enablesmoothsmoke, enablesmoothtemp, enablesmoothuvw, enablesmoothfuel – If checked the channel will be filtered.

Threshold | smoothtemp.x, smoothsmoke.x,smoothuvw.x,smoothfuel.x –  If this value is 0, the entire grid will be smoothed evenly. The higher the threshold is raised, the less voxels will be affected and only the sharpest gradients will be smoothed. The highest value you could use here depends on the range of the values of the smoothed channel - for Liquid it's usually in the [0,1] range, while for Velocity it could go as high as several hundred. If you set this value too high, no voxels will be smoothed at all.

Similarity | smoothtemp.y, smoothsmoke.y,smoothuvw.y,smoothfuel.y –  Increasing this value will allow you to smooth only the finer small-scale noise without changing the areas of the fluid which are already smooth. Note that just like the Threshold option, this value also depends on the range of the selected channel. If you want to remove only some sharp fine disturbances from the simulation without blurring other areas, set the Threshold to 0, increase the Similarity to the highest values the selected channel can take and then start reducing it until the small-scale noise is removed, while the larger fluid shapes are retained. This option won't take effect if the Threshold parameter is raised to the maximum. 

Random Variation | smoothtemp.z, smoothsmoke.z,smoothuvw.z,smoothfuel.z – This parameter introduces noise of uniform scale in the channel before smoothing is applied. This can be useful if you want to give the fluid a more homogeneous pattern and this way it can also help hide grid artifacts. Note that just like the Threshold option, this value also depends on the range of the selected channel. You can use this option to only add noise to the channel without smoothing it - in order to do this, set both Threshold and Similarity to the highest values of the selected channel and this way they will not take effect.

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Channels Mapping

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Different applications use different channels and might have different names for them. When loading f3d/vdb files, Phoenix tries to automatically make the conversion to the supported channels. If a channel is not mapped by default, a channel can be manually set from the dropdown menu. It can be accessed from the Cache Path menu when a 3rd party cache is loaded (e.g. .f3d or .vdb files).

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