DICOM segmentation dims CT brightness

[goddard@…]

The following bug report has been submitted:
Platform:        Darwin-18.7.0-x86_64-i386-64bit
ChimeraX Version: 0.91 (2019-08-05)
Description
Showing a DICOM CT scan in volume style and turning on a segmentation, channel makes the CT scan dimmer where the segmentation mask is all 0.  The segmentation brightness curve ramps from 0-1 over data values 0.5 to 1, so it should not make the CT dimmer outside the small segmented tumor region.  Moving the segmentation brightness curve even a tiny amount corrects the CT brightness.  Appears that turning on the segmentation did not correctly update blending.

Log:
UCSF ChimeraX version: 0.91 (2019-08-05)  
© 2016-2019 Regents of the University of California. All rights reserved.  
How to cite UCSF ChimeraX  

> open /Users/goddard/ucsf/data/dicom/11-06-2014-1-96508 format dicom

Opened multi-channel map CHEST CT 4, 10 channels, grid size 512,512,236, pixel
0.576,0.576,1.25, shown at step 1, values int16  
Opened CHEST CT 8, grid size 512,512,213, pixel 0.588,0.588,1.25, shown at
step 1, values int16  

> hide #!1.1.1.1.3 models

> hide #!1.1.1.1.2 models

> show #!1.1.1.1.2 models

> hide #!1.1.1.1.2 models

> show #!1.1.1.1.2 models




OpenGL version: 4.1 ATI-2.11.20
OpenGL renderer: AMD Radeon Pro 580 OpenGL Engine
OpenGL vendor: ATI Technologies Inc.

[Tom Goddard]

Fixed.

Blended 3d texture was created with initial rgba values, then the texture was filled with GPU code, and later the initial values were used to overwrite the texture. The code was supposed to use the GPU computed values and not assign any initial values and that is what it does now.