# Event
Event nodes are essential to trigger a stroke on ILIAD canvas.
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## Event on Step
This is the most used node to start a stroke. Steps are the distance covered in pixels when the tip of the stylus
touches the tablet (or when you use the left mouse button).
At each step, the brush will be calculated. If it is not a problem for simple brushes, it might make a brush very
low if it uses various and numerous nodes.
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## Event on Selected
After selecting a brush in ILIAD interface through Brush Selector, the Blueprint of this brush will be entirely
analysed to define and lock its behaviour. So, contrary to “Event on Step” that recalculates the brush at each step,
“Event on Selected” will calculate the aspect of the brush for once and for all after being loaded in Brush Selector.
This node is very useful to manage complex brushes (like a Bristle and its numerous hairs).
In the example below, we can see the brush as a single stamp, then as a stroke :
If we load again the brush, the stamp and the stroke are different :
If we edit the Blueprint and change “Event on Selected” for “Even on Step” : the brush changes at each step, which makes things very slow (we had to increase the step value, so you can see how the brush behaves).
When using the node “Event on Selected”, we strongly advise you to change the cache of your nodes from “Step” to “Super”.
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## Event on State Changed
Any Blueprint compilations and any changes made in ILIAD interface through modifiers (size, flow, step, etc.) and variables will force the brush to be calculated again. This node can be combined with “Event on Selected”.
We strongly advise you to change the cache of your nodes from “Step” to “State”.
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## Event on Stroke Begin / End
These nodes are very useful to call a specific stamp when your stroke starts and ends, which means
the moment when you click to draw / put the stylus down (begin) and the moment you drop the click / put the stylus up (end).
For instance, if you need to create an arrow with serif, the Blueprint will have to split the elements like this :
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## Event on Sub Stroke Begin / End
To explain these nodes, we must explain first what a substroke is. A substroke is an interval that composes a stroke.
Those intervals are spaced along the stroke in an irregular and unpredictable manner,
depending on the stroke itself (curves, orientation, etc). These nodes can be used to "randomly" pop a stamp along the main stroke.
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## Event on Tick
This node comes from Unreal Engine. It triggers events based on the refresh rate of Unreal Engine. At the moment, this node can’t really be used with ILIAD, but this might be useful in the future.
Iliad User Documentation 
