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IDProjectCategoryView StatusLast Update
0003869Slicer4Module VolumeRenderingpublic2014-10-10 07:57
ReporterlassoanAssigned Tofinetjul 
PrioritynormalSeverityminorReproducibilityalways
Status assignedResolutionopen 
Product Version 
Target VersionFixed in Version 
Summary0003869: Gradient opacity transfer function is not taken into account correctly in CPU volume ray caster
Description

When using VTK CPU Ray Casting mode in the volume rendering module, changing the gradient opacity transfer function has some effect (changes how the image looks) but it does not do the mapping correctly.

For example, load MRHead and set the following control points in the gradient opacity function (ramp):
Point; X; O
0; -10; 1.0
1; -5; 0.0
2; 25; 0.0
3; 80; 1.0

This produces a nice transparent image using Slicer-4.3.1 and creates an empty image using the latest Slicer trunk version.

(When using VTK CPU Ray Casting changing the gradient opacity transfer function has no effect at all.)

TagsNo tags attached.

Activities

2014-10-09 14:35

 

2014-10-09 14:37

 

lassoan

lassoan

2014-10-10 07:57

developer   ~0012611

Link to MRHead.nrrd sample file:
http://slicer.kitware.com/midas3/item/1697

Note on the gradient opacity transfer function: it is a simple ramp to implement high-pass filtering - opacity O=0.0 till x=25, increases linearly to O=1.0 till x=80, then O=1.0 remains constant for higher x values. On Slicer GUI opacity of the first point cannot be changed (it's 1.0), therefore we needed to add those points with negative x values to ensure O=0.0 at x=0.

Issue History

Date Modified Username Field Change
2014-10-09 14:33 lassoan New Issue
2014-10-09 14:33 lassoan Status new => assigned
2014-10-09 14:33 lassoan Assigned To => finetjul
2014-10-09 14:35 lassoan File Added: MRHeadWithGradientOpacity-Slicer4.3.1-OK.png
2014-10-09 14:37 lassoan File Added: MRHeadWithGradientOpacity-SlicerNightly-FAIL.png
2014-10-09 14:58 lassoan Summary Gradient opacity transfer function is not taken into account correctly in volume rendering => Gradient opacity transfer function is not taken into account correctly in CPU volume ray caster
2014-10-09 14:58 lassoan Description Updated
2014-10-10 07:57 lassoan Note Added: 0012611