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90 lines
2.8 KiB
Markdown
90 lines
2.8 KiB
Markdown
# Graphoon
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A force directed graph algorithm written in Lua.
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## Introduction
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_Graphoon_ emerged from the graph calculation code used in both [LoGiVi](https://github.com/rm-code/logivi) and [LoFiVi](https://github.com/rm-code/lofivi).
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A force directed graph layout is achieved by simulating physical forces, which push and pull each node in the graph until a nice layout is found.
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## Basic Usage
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The basic idea is that you create a new graph object, to which you can then add nodes and edges.
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```lua
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local GraphLibrary = require('Graphoon').Graph
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graph = GraphLibrary.new()
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graph:addNode( "Ash Williams" )
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graph:addNode( "Necronomicon" )
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graph:connectIDs( "Ash Williams", "Necronomicon" )
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```
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By itself Graphoon only provides functionality for creating the graph and calculating the layout based on physical attraction and repulsion forces.
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It provides a ```draw``` and ```update``` function, which can be used to easily write your own rendering code.
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The ```draw``` function should be called with two callback functions. The first callback will be used for all nodes and the second one for all the edges.
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```lua
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graph:draw( function( node )
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local x, y = node:getPosition()
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drawCircle( 'fill', x, y, 10 )
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end,
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function( edge )
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local ox, oy = edge.origin:getPosition()
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local tx, ty = edge.target:getPosition()
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drawLine( ox, oy, tx, ty )
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end)
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```
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At its simplest the force calculations can be updated via ```graph:update( dt )```, but the ```update``` function also can receive optional callbacks for both nodes and edges.
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## Advanced usage
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### Using anchors
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Anchors can be used to attach a node to a certain position on the screen. This can be useful if you want to center a certain node for example.
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This can either be done directly via the constructor of the node:
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```lua
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-- Anchor the node to the center of the screen.
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graph:addNode( "Ash Williams", screenX * 0.5, screenY * 0.5, true )
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```
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Or by using the ```setAnchor``` function:
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```lua
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-- Invert anchor status
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node:setAnchor( not node:isAnchor(), mouseX, mouseY )
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```
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### Using custom classes for Nodes and Edges
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If you prefer to not touch the default classes, you can simply inherit from them and tell Graphoon to use your custom classes instead.
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```lua
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local GraphLibraryNode = require('lib.libfdgraph.fd').Node
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local CustomNodeClass = {}
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-- You can pass additional arguments to your custom class. Just make sure the
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-- default parameters ar in the right order.
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function CustomNodeClass.new( id, x, y, anchor, ... )
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local self = GraphLibraryNode.new( id, x, y, anchor )
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-- ... Custom code
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end
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return CustomNodeClass
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```
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```lua
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local GraphLibrary = require('Graphoon').Graph
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GraphLibrary.setNodeClass( require('CustomNodeClass') )
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```
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