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This following parameters contains contain playback options you can use for retiming a cached sequence. Using these, you can speed up, slow down, or animate the motion of the sequence. When retiming, additional RAM may be used, and loading a new timeline frame may take longer when the frame must be obtained by creating a new one between two adjacent cache files. We will refer to the process of creating an intermediate frame from two caches as as Blending. 

Playback Mode – Chooses between different options for animation control:

Linear – This is the default mode. The cached 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 specifies which cache file will be loaded for the current timeline frame. Can be used to either show a static simulationstatic simulation, or the Direct Cache Index can be animated in case you want varying play speed, including playing the simulation in reverse.
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 a 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. 

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

Cache Origin – An offset specifying which cache file from the sequence is placed on the timeline at frame Timeline Origin.

Timeline Origin – An offset specifying which timeline frame the starting cache is placed on.

Play Speed – – A multiplier for the playback speed. Value A value of 1 means that each timeline frame corresponds exactly to one cache file index. If the play speed Play Speed is not exactly 1.0, frames are blended between by using the method specified by the the Blend Method parameter. Note that Play Speed is not keyable - you should switch to Cache Index mode and animate the Direct Cache Index if you want to animate.

Play Length – 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 – In Loop mode mode, this option specifies the number of timeline frames after the loop's end that are blended with the loop's beginning to create a smooth transition.  Keep in mind Remember 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 a Play Length of 20 and a Loop Overlap of 5, the transition frames start at frame 55 and 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 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 The correct setting of this value is especially important for simulations that contain particles. 

Grid Blend – Used 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 are blended again. You can choose between three different methods for blending between cache files:

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 is also slower. Captures the movement of the fronts of the plumes well , but does not work well for smoke moving backward, and also may produce flickering. It requires a velocity channel.
Precise Tracing – – Improved Velocity-based interpolation for Fire and Smoke simulations. Captures plume movement very well and can handle very low Play Speeds. Requires a Velocity channel, as well as an Advection Origin channel.

Load Nearest If Missing – 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 – – When enabled, flips the Y and Z axis of the cached transformation. This is useful when the cache was created with a different up-axis (for example, in 3ds Max).

The following controls allow you to smooth the grid channels loaded from cache files for preview and rendering. You can use this to prevent grid artifacts on meshed grid channels such as the Liquid surface, Smoke or Temperature, to remove unwanted noise in these channels, or to get smooth motion blur by smoothing the Velocity grid channel.

Smooth Threshold – If this value is 0, the entire grid is smoothed evenly. The higher the threshold is raised, the fewer voxels are affected and only the sharpest gradients are smoothed. The highest value you could use here depends on the range of the values of the smoothed channel – for Smoke it's usually in the [0,1] range, while for Velocity it could go as high as several hundred and for Temperature it could be over a thousand. If you set this value too high, no voxels are smoothed at all.

Smooth Similarity – Increasing this value allows 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. 

Smooth Randomization – 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 add only 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 do not take effect.