text: var PositionNode = require('./nodes/PositionNode');
  var Graph = require('./Graph');
  var Uniform = require('./Uniform');
  var Attribute = require('./Attribute');
  
  module.exports = VertexGraph;
  
  function VertexGraph(options){
  	options.mainNode = options.mainNode || new PositionNode();
  	Graph.call(this, options);
  }
  VertexGraph.prototype = Object.create(Graph.prototype);
  
  VertexGraph.prototype.getUniforms = function(){
  	var uniforms = Graph.prototype.getUniforms.apply(this);
  	uniforms.push(
  		new Uniform({
  			name: 'viewProjectionMatrix',
  			type: 'mat4',
  			defaultValue: 'VIEW_PROJECTION_MATRIX'
  		}),
  		new Uniform({
  			name: 'worldMatrix',
  			type: 'mat4',
  			defaultValue: 'WORLD_MATRIX'
  		})
  	);
  	return uniforms;
  };
  
  VertexGraph.prototype.getAttributes = function(){
  	var attributes = Graph.prototype.getAttributes.apply(this);
  	attributes.push(new Attribute({
  		name: 'vertexPosition',
  		defaultValue: 'POSITION',
  		type: 'vec3'
  	}));
  	return attributes;
  };