Node: onBefore, onAfter events

[Samsy]

Description

Callbacks before a node is rendered, and after a node is rendered would be extremely useful to set renderer state such as autoClear etc.. but also helping for custom instructions

For example

a reflector, or water, if we need to setup a camera layer before those actually renders for selective render inside a reflector
this requires a callback before and after the node actually renders

An issue I mentionned here :
#30197

Solution

Provide a onBeforeNode, and onAfterNode render

[Mugen87]

Are you aware of the existing possibilities to implement such use cases? The idea is to derive from the built-in node classes and then implement the already existing update methods.

three.js/src/nodes/core/Node.js

Lines 532 to 558 in eb8c334

	/**
	* The method can be implemented to update the node's internal state before it is used to render an object.
	* The {@link Node#updateBeforeType} property defines how often the update is executed.
	*
	* @abstract
	* @param {NodeFrame} frame - A reference to the current node frame.
	* @return {Boolean?} An optional bool that indicates whether the implementation actually performed an update or not (e.g. due to caching).
	*/
	updateBefore( /*frame*/ ) {
	console.warn( 'Abstract function.' );
	}
	/**
	* The method can be implemented to update the node's internal state after it was used to render an object.
	* The {@link Node#updateAfterType} property defines how often the update is executed.
	*
	* @abstract
	* @param {NodeFrame} frame - A reference to the current node frame.
	* @return {Boolean?} An optional bool that indicates whether the implementation actually performed an update or not (e.g. due to caching).
	*/
	updateAfter( /*frame*/ ) {
	console.warn( 'Abstract function.' );
	}

To let the methods executed per render, you must set node.updateBeforeType and node.updateAfterType to NodeUpdateType.RENDER.

[Samsy]

Hey @Mugen87

Thanks for the answer, I was not aware of this mechanism, as it isn't mentioned in the wiki, and not once in the examples !

I'll look at it, many thanks

[Mugen87]

If you need more examples for this pattern, check out the post processing modules in examples/jsm/tsl/display. They use these methods all over the place.

[Samsy]

Thanks @Mugen87