Use hair caches

You simulate hair by playing through the time slider (see Play a hair simulation). You can create a cache file to store all the positions of the hair curves during the simulation. This cache lets you quickly preview the results of the hair simulation without having to render. This offers many benefits, including scrubbing back and forth in the time slider and re-using a cache so you don't have to solve at render time.

The main purpose of the cache is for batch render so that you can do distributed rendering and have the simulation match exactly.

See Rendering using distributed render.

Specifically you can:

Create a hair cache

To create a hair cache

Select the hair system.
Do one of the following:
- SelectnHair > Create Cache.
- Select nHair > Create Cache > , set the time range and sampling settings and then click Create.

You can select from the following options:

Cache Time Range: Select a time range for the cache. Use the time range as specified in the Render Settings or the Time Slider, or set a new time range with the Start/End option.
Sampling: Specify either Over or Under for sampling and then set a Rate value for sampling. The default value for Rate is 1.

Append to a hair cache

You can use Append to Cache to add the specified frames to the existing cache. If the range of frames you specify occurs earlier than the last frame in the cache, the overlapping frames are overwritten. You may want to append to a hair cache if you decide to render more frames than you originally had cache for.

You might use the “append and truncate a cache” workflow if you're hand-tweaking the behavior of your hair. For example, cache a simulation for a while, truncate it at or before the frame where some hairs do something you don't want, modify some attributes, cache for a while again until you notice some behavior that you want to change. See To truncate a hair cache.

To append to a hair cache

Select the hair system.
Select nHair > Append to Cache > . The Append to Hair Cache Options window appears.

You can select from the following options:

Append Time Range: Select a time range to append to the cache. Use the Current Time (applies a single frame), Current Time to Time Slider End, or set a new time range with the Start/End option.
Sampling: Specify either Over or Under for sampling and then set a Rate value for sampling. The default value for Rate is 1.

Set the append options and then click the Append button.
Maya appends the new cache information to the existing cache file for the hair system according to the options you set.

Truncate a hair cache

You may want to truncate a cache for one of the following reasons:

If your modifications only start affecting the behavior of your hair dynamics partway through the cache, and you only want to re-cache form the point where it changes.
If you don't want or need the tail end of your simulation.

To truncate a hair cache

Select the hair system with the cache you want to truncate.
In the Time Slider move to the frame where you want to truncate the cache.
Select nHair > Truncate Cache. Maya deletes the cache from the current frame forward.

Delete a hair cache

You may want to delete your hair cache for one of the following reasons:

If you modify a dynamic hair simulation after caching, you must disable or delete the cache so that the modifications appear when you play the hair simulation.
You must re-create the cache before you (distributed) render your hair.
You can delete the cache to free up disk space.

To delete a hair cache

Select nHair > Delete Cache. The existing hair cache is removed.

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