Changes between Initial Version and Version 1 of Ticket #8183


Ignore:
Timestamp:
Dec 13, 2022, 6:30:38 PM (3 years ago)
Author:
Tom Goddard
Comment:

Setting the transparency depth to be a smaller fraction of the total thickness (default is 0.5)

volume #1 transparency 0.1

has the bad effect of making the linear part of the brightness curve ramping from 0 up to 1 much more opaque. Also almost no user is aware of this parameter so having them directly modify it is not feasible.

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  • Ticket #8183

    • Property Component Unassigned → Volume Data
    • Property Owner set to Tom Goddard
    • Property Platform → all
    • Property Project → ChimeraX
    • Property Status new → assigned
    • Property Summary ChimeraX bug report submission → Volume image opacity is too sensitive where brightness curve is near top of histogram
    • Property Type defect → enhancement

  • Ticket #8183 – Description

    initial v1  
    44ChimeraX Version: 1.6.dev202211082330 (2022-11-08 23:30:49 UTC)
    55Description
     6
    67Opacity changes  in image style volume rendering are too sensitive when many planes are shown (e.g. 100) and the transfer function is near 1 (top of histogram).  It goes from rather transparent to fully opaque with just a tiny change of height of the brightness curve on the histogram.
     8
     9The per-plane opacity is determined as alpha_plane = 1 - (1-alpha_curve)**(1/nplanes).  The nplanes equals the number of displayed planes times the transparency depth parameter (default 0.5).  If nplanes = 100 and alpha_curve = 0.99 then alpha_plane =  0.045.  To get alpha_plane close to 1 requires an absurdly close alpha_curve value to 1, for instance alpha_curve = 1 - 1e-30 gives alpha_plane = 0.5.
     10
     11The interactive adjustment of the brightness curve height works very poorly to control opacity near height 1.
     12
    713
    814Log: