Editing Volume rendering (section)

===Shear warp===
[[Image:volRenderShearWarp.gif|thumb|250px|Example of a mouse skull (CT) rendering using the shear warp algorithm]]

The shear warp approach to volume rendering was developed by Cameron and Undrill, popularized by Philippe Lacroute and [[Marc Levoy]].<ref>{{Cite book|url = http://graphics.stanford.edu/papers/shear/|publisher = ACM|date = 1994-01-01|location = New York, NY, USA|isbn = 978-0897916677|pages = 451–458|doi = 10.1145/192161.192283|first1 = Philippe|last1 = Lacroute|first2 = Marc|last2 = Levoy| title=Proceedings of the 21st annual conference on Computer graphics and interactive techniques - SIGGRAPH '94 | chapter=Fast volume rendering using a shear-warp factorization of the viewing transformation |citeseerx = 10.1.1.75.7117| s2cid=1266012 }}</ref> In this technique, the [[viewing transformation]] is transformed such that the nearest face of the volume becomes axis aligned with an off-screen image [[data buffer]] with a fixed scale of voxels to pixels.  The volume is then rendered into this buffer using the far more favorable memory alignment and fixed scaling and blending factors.  Once all slices of the volume have been rendered, the buffer is then warped into the desired orientation and scaled in the displayed image.

This technique is relatively fast in software at the cost of less accurate sampling and potentially worse image quality compared to ray casting. There is memory overhead for storing multiple copies of the volume, for the ability to have near axis aligned volumes. This overhead can be mitigated using [[run length encoding]].