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On volume rendering algorithm(B)
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Abstract
The Shear-warp is one important Splattinng Volume Rendering Algorithm, which speeds up the algorithm remarkably with the introduction of the middle projection plane and has extensive applications in medically graphical processing. This paper focuses on the analysis of this algorithm, detailed discussions of the two reasons for the graphical distortion generated by shear-warp and the presentation of an efficient improvement method.
There are two reasons related to the graphical distortion caused by the application of shear-warp algorithm. Firstly, shear-warp adopts two-step sampling. It renders the volumetric data to the middle projection plane, and then gets the final drawing by warp. The paralleling of the middle projection plane and the data tangent plane at the first step brings errors to the calculating of sampling points. The value of error function changes as well as vision angle, which is proved by strict mathematical derivation in this paper. The second reason is that the algorithm gets the value of sampling points with the method of planar linearity interpolation, neglecting the profound information in the tangent plane’s vertical direction. From a visual example, this paper proves that when the changing frequency of volumetric data is too violent, planar linearity interpolation will raise drawing distortion.
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