Název:	Fast opacity control in rendering of volumetric CT data
Autoři:	Csébfalvi, Balázs Szirmay-Kalos, László Márton, Gábor
Citace zdrojového dokumentu:	Journal of WSCG. 1997, vol. 5, no. 1-3.
Datum vydání:	1997
Nakladatel:	Václav Skala - UNION Agency
Typ dokumentu:	článek article
URI:	http://wscg.zcu.cz/wscg1997/wscg97.htm http://hdl.handle.net/11025/15927
ISSN:	1213-6972 (print) 1213-6980 (CD-ROM) 1213-6964 (online)
Klíčová slova:	objemové vykreslování;alpha blending;sledování paprsku;lékařské zobrazování;CT
Klíčová slova v dalším jazyce:	volume rendering;alpha blending;ray tracing;medical imaging;CT
Abstrakt v dalším jazyce:	In 3D rendering of volumetric CT data the alpha-blending technique can be used for modeling semitransparent tissues. This method assigns di erent opacity values to di erent tissue types. In practice, only four materials can be separated according to their CT numbers (Hounsfield density): air, fat, soft tissue and bone. Application of alpha-blending rendering enhances the more important tissues, assigning high opacity value for important tissues and low opacity for less important ones. For each pixel of the image, a ray is traced and the colour of the appropriate pixel is computed as a sum of intersected voxel colours weighted by opacity values. However, this computation is very slow if the size of 3D array is big. Furthermore, if the opacity value of one of the tissues needs to be changed, then the complete time-consuming rendering must be repeated in order to recompute the new weighted sums. In order to allow fast control of opacity values of a new algorithm is presented that provides fast opacity and colour modification after preprocessing the volume with fixed point of view and light source locations.
Práva:	© Václav Skala - UNION Agency
Vyskytuje se v kolekcích:	Volume 5, number 1-3 (1997)

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