diff --git a/examples/GLBarGraphItem.py b/examples/GLBarGraphItem.py
new file mode 100644
index 00000000..d14eba87
--- /dev/null
+++ b/examples/GLBarGraphItem.py
@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+"""
+Demonstrate use of GLLinePlotItem to draw cross-sections of a surface.
+
+"""
+## Add path to library (just for examples; you do not need this)
+import initExample
+
+from pyqtgraph.Qt import QtCore, QtGui
+import pyqtgraph.opengl as gl
+import pyqtgraph as pg
+import numpy as np
+
+app = QtGui.QApplication([])
+w = gl.GLViewWidget()
+w.opts['distance'] = 40
+w.show()
+w.setWindowTitle('pyqtgraph example: GLBarGraphItem')
+
+gx = gl.GLGridItem()
+gx.rotate(90, 0, 1, 0)
+gx.translate(-10, 0, 10)
+w.addItem(gx)
+gy = gl.GLGridItem()
+gy.rotate(90, 1, 0, 0)
+gy.translate(0, -10, 10)
+w.addItem(gy)
+gz = gl.GLGridItem()
+gz.translate(0, 0, 0)
+w.addItem(gz)
+
+# regular grid of starting positions
+pos = np.mgrid[0:10, 0:10, 0:1].reshape(3,10,10).transpose(1,2,0)
+# fixed widths, random heights
+size = np.empty((10,10,3))
+size[...,0:2] = 0.4
+size[...,2] = np.random.normal(size=(10,10))
+
+bg = gl.GLBarGraphItem(pos, size)
+w.addItem(bg)
+
+
+## Start Qt event loop unless running in interactive mode.
+if __name__ == '__main__':
+    import sys
+    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
+        QtGui.QApplication.instance().exec_()
diff --git a/pyqtgraph/PlotData.py b/pyqtgraph/PlotData.py
index 0bf13ca8..e5faadda 100644
--- a/pyqtgraph/PlotData.py
+++ b/pyqtgraph/PlotData.py
@@ -15,6 +15,7 @@ class PlotData(object):
         - removal of nan/inf values
       - option for single value shared by entire column
       - cached downsampling
+      - cached min / max / hasnan / isuniform
     """
     def __init__(self):
         self.fields = {}
diff --git a/pyqtgraph/multiprocess/remoteproxy.py b/pyqtgraph/multiprocess/remoteproxy.py
index f33ebc83..e4c3f34f 100644
--- a/pyqtgraph/multiprocess/remoteproxy.py
+++ b/pyqtgraph/multiprocess/remoteproxy.py
@@ -205,7 +205,11 @@ class RemoteEventHandler(object):
                             fnkwds[k] = np.fromstring(byteData[ind], dtype=dtype).reshape(shape)
                 
                 if len(fnkwds) == 0:  ## need to do this because some functions do not allow keyword arguments.
-                    result = obj(*fnargs)
+                    try:
+                        result = obj(*fnargs)
+                    except:
+                        print("Failed to call object %s: %d, %s" % (obj, len(fnargs), fnargs[1:]))
+                        raise
                 else:
                     result = obj(*fnargs, **fnkwds)
                     
diff --git a/pyqtgraph/opengl/GLGraphicsItem.py b/pyqtgraph/opengl/GLGraphicsItem.py
index 59bc4449..9680fba7 100644
--- a/pyqtgraph/opengl/GLGraphicsItem.py
+++ b/pyqtgraph/opengl/GLGraphicsItem.py
@@ -40,6 +40,7 @@ class GLGraphicsItem(QtCore.QObject):
         self.__glOpts = {}
         
     def setParentItem(self, item):
+        """Set this item's parent in the scenegraph hierarchy."""
         if self.__parent is not None:
             self.__parent.__children.remove(self)
         if item is not None:
@@ -98,9 +99,11 @@ class GLGraphicsItem(QtCore.QObject):
         
     
     def parentItem(self):
+        """Return a this item's parent in the scenegraph hierarchy."""
         return self.__parent
         
     def childItems(self):
+        """Return a list of this item's children in the scenegraph hierarchy."""
         return list(self.__children)
         
     def _setView(self, v):
@@ -124,10 +127,15 @@ class GLGraphicsItem(QtCore.QObject):
         return self.__depthValue
         
     def setTransform(self, tr):
+        """Set the local transform for this object.
+        Must be a :class:`Transform3D <pyqtgraph.Transform3D>` instance. This transform
+        determines how the local coordinate system of the item is mapped to the coordinate
+        system of its parent."""
         self.__transform = Transform3D(tr)
         self.update()
         
     def resetTransform(self):
+        """Reset this item's transform to an identity transformation."""
         self.__transform.setToIdentity()
         self.update()
         
@@ -148,9 +156,12 @@ class GLGraphicsItem(QtCore.QObject):
             self.setTransform(tr * self.transform())
         
     def transform(self):
+        """Return this item's transform object."""
         return self.__transform
         
     def viewTransform(self):
+        """Return the transform mapping this item's local coordinate system to the 
+        view coordinate system."""
         tr = self.__transform
         p = self
         while True:
@@ -190,16 +201,24 @@ class GLGraphicsItem(QtCore.QObject):
     
     
     def hide(self):
+        """Hide this item. 
+        This is equivalent to setVisible(False)."""
         self.setVisible(False)
         
     def show(self):
+        """Make this item visible if it was previously hidden.
+        This is equivalent to setVisible(True)."""
         self.setVisible(True)
     
     def setVisible(self, vis):
+        """Set the visibility of this item."""
         self.__visible = vis
         self.update()
         
     def visible(self):
+        """Return True if the item is currently set to be visible.
+        Note that this does not guarantee that the item actually appears in the
+        view, as it may be obscured or outside of the current view area."""
         return self.__visible
     
     
@@ -237,6 +256,10 @@ class GLGraphicsItem(QtCore.QObject):
         self.setupGLState()
         
     def update(self):
+        """
+        Indicates that this item needs to be redrawn, and schedules an update 
+        with the view it is displayed in.
+        """
         v = self.view()
         if v is None:
             return
diff --git a/pyqtgraph/opengl/MeshData.py b/pyqtgraph/opengl/MeshData.py
index 12a9b83b..71e566c9 100644
--- a/pyqtgraph/opengl/MeshData.py
+++ b/pyqtgraph/opengl/MeshData.py
@@ -247,9 +247,9 @@ class MeshData(object):
             return self._faceNormals
         elif indexed == 'faces':
             if self._faceNormalsIndexedByFaces is None:
-                    norms = np.empty((self._faceNormals.shape[0], 3, 3))
-                    norms[:] = self._faceNormals[:,np.newaxis,:]
-                    self._faceNormalsIndexedByFaces = norms
+                norms = np.empty((self._faceNormals.shape[0], 3, 3))
+                norms[:] = self._faceNormals[:,np.newaxis,:]
+                self._faceNormalsIndexedByFaces = norms
             return self._faceNormalsIndexedByFaces
         else:
             raise Exception("Invalid indexing mode. Accepts: None, 'faces'")
diff --git a/pyqtgraph/opengl/items/GLMeshItem.py b/pyqtgraph/opengl/items/GLMeshItem.py
index 66d54361..5b245e64 100644
--- a/pyqtgraph/opengl/items/GLMeshItem.py
+++ b/pyqtgraph/opengl/items/GLMeshItem.py
@@ -69,7 +69,11 @@ class GLMeshItem(GLGraphicsItem):
         self.update()
         
     def shader(self):
-        return shaders.getShaderProgram(self.opts['shader'])
+        shader = self.opts['shader']
+        if isinstance(shader, shaders.ShaderProgram):
+            return shader
+        else:
+            return shaders.getShaderProgram(shader)
         
     def setColor(self, c):
         """Set the default color to use when no vertex or face colors are specified."""