i have certain datasets which are unsigned char type who's colors have
been assigned (i.e., all the values that represent a structure are, say,
250, all the values that represent another structure are 251).
when i apply a 256 element RGBA float colormap to this volume with all
LUT elements black and completely transparent except for 250 and 251, things
appear to be as one would expect. two blobs of two different colors.
however, when i apply a 256 element RGBA color map that contains a linear
gray-scale ramp, exept for elements 250 & 251 (which retain the values of
the earlier colormap), i get two blobs that are *shrouded* in gray. this
shroud extends very far from the data values in the volume. if i clamp
the colorLUT applied so values above 80 or 100 are all black/transparent,
there is still a faint grey shroud, roughly describing the boudaries of the
two structures.
i've checked the voxel values as they are read into my Volumizer class.
lots of voxels with value 0, and some with 250 and 251 is all.
i've also made sure that args 2 and 3 below are 0 and 255.
// expand the values to span the whole dymanic range
voAppearanceActions::dataScaleRange(brick, pvdata->rangeLo,
pvdata->rangeHi);
i've tried removing this function call altoghether. still i get smearing
down into voxel values that don't exist.
i also see some slight color crossover between the two structures.
anything obvious come to mind that might be causing this?
thanks.
--fred
--
Fred Dech fdech@uic.edu
Network Analyst
Virtual Reality in Medicine Laboratory : VRMedLab
University of Illinois at Chicago : UIC
(312) 413-3092: fax (312) 996-8342
