Modifier (lxu-modifier.hpp)

This module provides utility classes for creating EvalModifier servers.

CLxItemModifierElement & CLxItemModifierServer

These classes are used to implement a fairly general-purpose modifier. The only assumption it makes is that there is one modifier node for each item of a specific type.

Server

The client subclasses the server type and defines these two virtual methods to declare their behaviors.

• ItemType() -- returns the name of the item type for this modifier
• GraphNames() -- returns a list of space-separated graph names that trigger this modifier to update (optional)

When a modifier node is added for an item, this method is called. It returns the element object that the client has also subclassed

• Alloc() -- allocate element using the Evaluation Interface to select channels to read and write

Element

The element is subclassed to perform the operation of the modifier by overriding these virtual methods.

• Eval() -- reads from input channels and writes to output(s)
• Test() -- returns false if this element no longer matches the state of the scene (defaults to true)

The element can also maintain cached state so that it can do incremental updates.

• Cache() -- returns new cache object (derived from CLxObject)
• EvalCache() -- if this modifier uses caches, then this method is called instead of Eval()
• Validate() -- called when an input channel has been re-validated, with its change code (optional)

Initialization

Adding the server is done with a special constructor which does the right voodoo given the server class and name.

initialize ()
{
	CLxExport_ItemModifierServer<CMyModifier> ("myModifier");
}

CLxObjectRefModifierCore

This class is used to create somewhat simpler modifiers whose only purpose is to set object channels on items. These are also configured by virtual methods:

• ItemType() -- name of the item type
• Channel() -- name of the OBJREF channel
• Attach() -- add channels for reading
• Alloc() -- read inputs and allocate the destination object

It supports a similar initialization function.

initialize ()
{
	CLxExport_ItemModifierServer<CLxObjectRefModifier<CMyCore> > ("myModifierServer");
}

CLxRenderCamera

Utility class for accessing the current render camera. The method support reading the camera index inside a modifier.