____________________________________________________________________
header > abstract > paper > figures > footer

Mastering Perspective Projection through Parallelly Projected Slabs for Virtual Endoscopy

by A. Vilanova, R. Wegenkittl, A. König and E. Gröller.
Published in SCCG'01-Spring Conference on Computer Graphics, Conference Proceedings, pages 287-295, April 2001.

This page assembles some results (figures) of work that is part of our research topic ``Visualization of Medical Data''. The figures are provided in GIF or JPG format and the movies are MPEG1 compressed (m1v).



____________________________________________________________________
header < abstract > paper > figures > footer

Abstract of the Paper:

Virtual Endoscopy is a promising medical application for volume rendering techniques where perspective projection is mandatory. Most of the acceleration techniques for direct volume rendering make use of parallel projection. This is also the case of the current generation of VolumePro systems, which achieve real-time frame rates but unfortunately just provide parallel projection. In this paper, an algorithm to approximate perspective volume rendering using parallelly projected slabs is presented. The introduced error due to the approximation is investigated. Based on the error estimation, an improvement to the basic algorithm is presented. The improvement increases the frame rate keeping the global maximal error bounded. The usability of the algorithm is shown through the virtual endoscopic investigation of various types of medical data sets.



____________________________________________________________________
header < abstract < paper > figures > footer

Download the paper (.ps.zip) (~467KB)

Download the paper (.pdf) (~735KB)

Version to be published in The Journal of Visualization & Computer Animation Download the paper (.ps.zip) (~449KB)



____________________________________________________________________
header < abstract < paper < figures > footer

Animations

Figures in the paper

[Fig. 1]
 		Figure 1 :
Illustration of the perspective approximation using the projected-slabs algorithm.
[Fig. 2]
 		Figure 2 :
Accumulated values in a correct perspective projection as compared to the projected-slabs algorithm.
[Fig. 3]
 		Figure 3 :
Illustration of the error estimation.
[Fig. 4]
 		Figure 4 :
Comparison of the slabs using constant thickness and the incremental slab thickness calculation.
[Fig. 5]
[Fig. 5] 		Figure 5a and Figure 5b :
An illustration of the error tolerance behaviour. Two endoscopic views using the projected-slabs algorithm of a voxelized tube are shown together with the corresponding outside view with the slab image planes. The error tolerance is different for each endoscopic view:
a) (top) DistanceError = 5% of the image size.
b) (bottom) DistanceError = 2% of the image size.
[Fig. 6][Fig. 6][Fig. 6] Figure 6a and Figure 6b and Figure 6c:
Visualization of the CT trachea data set of a corpse compared to a real endoscopic view:
a) (left) Projected-slabs algorithm with incremental slab thickness (37 slabs).
b) (middle) Projected-slabs algorithm with constant slab thickness equal to one voxel distance (162 slabs).
c) (right) Real bronchoscopy snapshot.
[Fig. 7][Fig. 7][Fig. 7] Figure 7a and Figure 7b and Figure 7c:
CT trachea data set rendered with different transfer functions. From (left) to (right) from opaque to transparent trachea walls.
[Fig. 8][Fig. 8][Fig. 8] Figure 8a and Figure 8b and Figure 8c:
Spiral CT colon data set visualization:
a) (left) Projected-slabs algorithm with incremental slabs thickness (28 slabs).
b) (middle) Projected-slabs algorithm with constant slab thickness and with the maximal error equal to a (179 slabs).
c) (right) Brute force ray casting algorithm.



____________________________________________________________________
header < abstract < paper < figures < footer

This page was last updated by Anna Vilanova on November 26, 2001.
If you have any comments, please send a message to anna@cg.tuwien.ac.at.