Example of volume rendering

gistfile1.txt

def toggleVolumeRenderVisibility(self, visible):
    volumeNode = <volume node however you get it>
    NodeCombo = slicer.util.findChild(self.volumerenderWidget, 'VolumeNodeComboBox')
    VisibilityCheckBox = slicer.util.findChild(self.volumerenderWidget, 'VisibilityCheckBox')
    volRenLogic = slicer.modules.volumerendering.logic()

    if volumeNode is not NodeCombo.currentNode():      
      displayNode = volRenLogic.CreateDefaultVolumeRenderingNodes(volumeNode)
      displayNode.SetVisibility(visible)
      displayNode.GetVolumePropertyNode().Copy(volRenLogic.GetPresetByName("CT-AAA"))   
      AutoReleaseGraphicsResourcesCheckBox = slicer.util.findChild(self.volumerenderWidget, 'AutoReleaseGraphicsResourcesCheckBox')
      QualityControlComboBox = slicer.util.findChild(self.volumerenderWidget, 'QualityControlComboBox')          
      NodeCombo.setCurrentNode(volumeNode)
      AutoReleaseGraphicsResourcesCheckBox.checked = True
      QualityControlComboBox.currentText = 'Adaptive'
    
    VisibilityCheckBox.checked = visible