Caching agents - Houdini

In Atoms you can save your simulation on disk using the Atoms cache, then it is possible to reuse these caches with the "cacheReader" behaviour module. The Atoms Cache is lightweight and fast. It can increase the performances of your scene dramatically compared to using live simulation.

With the cache reader and the agents layout tool you can edit and tweak your cache.

Exporting a cache

You can open the cache exporter GUI using the shelf button or via the Atoms Menu: Atoms > Export > Cache Exporter

Create an agent group
Add a grid layout behaviour module and set the size attribute to (5,1,5)
Add a state machine behaviour module and set the state attribute to 1
Create some other agent groups and move them
Open the cache exporter form the Atoms menu: Atoms > Export > Cache Exporter
Select the agent groups you have created from the list, then choose a path where your cache will be saved.
Finally select your start and end frame.
Click on the "Export" button.

Importing a cache

You can import a cache in a scene using the cacheReader behaviour module

Create and agent group.
Add a cacheReader behaviour module.
in the cachePath attribute of the cache reader module pick the cache file (the file named youCacheName.atoms)
Rewind the scene and atoms will load the cache. It also automatically load all the agent types that are missing from your scene.
You can create multiple agent group to load different caches or the same cache multiple times. You can also move then around and rotate them.

Editing a cache

When a cache is loaded in your scene you can still edit it to change your layout or simulation.

Apply a new height field

Even if you exported the cache from some agent groups on a height field you can apply a new height field to your cache

Create a new height field
Create an agent group and import your cache using the cacheReader behaviour module
In the height field attribute of the cache reader module set the new height field name you created
Rewind the scene or press UpdateSim from the shelf and press play

Move agents

Create an agent group and import your cache using the cacheReader behaviour module
To move agents you can use the transitionOffset attribute or you can use the Agents Layout Tool
Select the agent group and activate the agents layout tool from the Atoms menu: Atoms → Tools → Agents Layout Tool or just press enter
Press Q to switch to the selection mode or press
from the agent layout tool ui (press P to show the ui)
Select the agents you want move
Press A to switch to the move mode or press
from the ui
Use the manipulator to move the agents where you want
Rewind the scene or press UpdateSim from the shelf and press play

Rotate agents

Create an agent group and import your cache using the cacheReader behaviour module
To rotate agents you can use the rotationOffset attribute or you can use the Agents Layout Tool
Select the agent group and activate the agents layout tool from the Atoms menu: Atoms → Tools → Agents Layout Tool
Press Q to switch to the selection mode or press
from the agent layout tool ui (press P to show the ui)
Select the agents you want rotate
Press Z to switch to the rotate mode or press
from the ui
Press the LMB and move the mouse on the left or on the right to rotate the agents or press SHIFT+LMB to rotate around the group pivot
Rewind the scene or press UpdateSim from the shelf and press play

Delete agents

Create an agent group and import your cache using the cacheReader behaviour module
To delete agents you can use the filterAgent attribute (set value of 1 to remove an agent) or you can use the Agents Layout Tool
Select the agent group and activate the agents layout tool from the Atoms menu: Atoms → Tools → Agents Layout Tool
Press Q to switch to the selection mode or press
from the ui
Select the agents you want delete
And from the ui press the "Delete Selected Agents" button
Rewind the scene or press UpdateSim from the shelf and press play

Change agents speed

You can also change the agent speed changing the frameRate attribute. This attribute is a multiplier on the input time.

Create an agent group and import your cache using the cacheReader behaviour module
To change the speed of some agents open the override agent dialog
next to frameRate attribute
Select the agents you want modify form the list or use the Agents Layout Tool to select the agents (the selection inside the override dialog changes automatically)
Set a value of 0.5 in the value field and then press "Set Value" button
Rewind the scene or press UpdateSim from the shelf and press play

Offset frame

You can offset the cache frame for each agent, so an agent can start playing at frame 10 instead of frame 0.

Create an agent group and import your cache using the cacheReader behaviour module
To offset the start frame of some agents open the override agent dialog
next to frameOffset attribute
Select the agents you want modify form the list or use the Agents Layout Tool to select the agents(the selection inside the override dialog changes automatically)
Set a value of 10 in the value field and then press "Set Value" button
Rewind the scene or press UpdateSim from the shelf and press play

Duplicate agents

You can clone agents inside a cache

Create an agent group and import your cache using the cacheReader behaviour module
Select the agent group and activate the agents layout tool from the Atoms menu: Atoms → Tools → Agents Layout Tool
Press Q to switch to the selection mode or press
from the ui
Select the agents you want duplicate
Press the "Duplicate selected agents" button
Atoms duplicates the selected agents with an offset
Press A to switch to move mode or press
and move the new agents where you want
Rewind the scene or press UpdateSim from the shelf and press play

Resim agents

The cache reader module gives you the possibility to simulate again any agent, so you can apply direction modules and so on.

Create an agent group and import your cache using the cacheReader behaviour module
Select the agent group and activate the agents layout tool from the Atoms menu: Atoms → Tools → Agents Layout Tool
Press Q to switch to the selection mode or press
or RMB on the viewport and choose Select mode
Select some agents
Open the override agent dialog
next to directionFromCache attribute
Set a value of 0
Create a curve near the selected agents
Add a follow curve module
Attach the curve to the follow curve module
Rewind the scene and press play, now the selected agents will follow the curve

Using the Cache manager

When you use the cache reader module Atoms stores some frames of your cache in memory while playing the simulation to improve performances. You can use the Cache manager UI to load in advance caches and increase the max memory amount reserved by the cache manager. Please look at the cache manager section for more information.