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wrote the tutorial for SSAO (without images)
link to example fixed in tutorial (ssao)
Merge branch 'master' of https://github.com/x3dom/x3dom

Conflicts:
	doc/x3doc/base/tutorials/lighting/ssao/index.html

Also added the missing comparison image for the SSAO tutorial.
Improved the edge enhancement volume style
Testing improvements on the Cartoon rendering style and ammending the previous commit
Allowing to use the toneMapped style on the IsoSurfaceVolumeData and corrections on the ToneMappedVolumeStyle
Changed the gradient transformation and deleted the blue enhancement
Correction on the volume rendering styles
Update the way segments are identified
Fixed bug, surfaceTolerance paramater was not being taken into account and changed
the way opacity is being accumulated
Change, using the GLSL built-in functions to check if the position is inside the bounding box and discard the fragment if not
Allowing to change the opacityFactor and lightFactor with the OpacityMapVolumeStyle on each segment, when using the SegmentedVolumeData
Optimized unnecesary operation
Corrected again the tonemapped
Avoid unnecesary surfacenormals calculation when only using the OpacityMapVolumeStyle on a scene
Correcting the lightAssigment parameters
Added regression test case, that checks if the an style is rendering correctly when the gradient is calculated on the fly
Merge pull request #458 from fbrandherm/master

SSAO Tutorial
Merge pull request #457 from aarbelaiz/volren-style-corrections

Volume redering style node corrections