clip caps not correct after "volume level"

[olibclarke@…]

Clip caps are not correct after using "volume level" to change the contouring level. E.g.:

open emdb:28533
use Side View to clip the front
volume #1 level 0.004

The caps are too small for the contours, but correct themselves if you turn the clipping model display off and on in the model panel. Conversely, the caps are too big if you increase the contour level (though that's harder to see directly).

This problem may be the reason for case #3 in ticket #9887. Certainly it's at least a part of the problem. Once this is fixed, we can see if that also fixes #9887.

[Tom Goddard]

It is easy to reproduce this. It seems the clip cap update doesn't happen when the volume level is changed by command. Hiding and showing the volume model fixes it. Even dragging the histogram level updates the clip cap but leaves it at the position of the second to last shown surface. When using the near clipping plane, any motion of the scene with the mouse fixes the cap. That is probably why no one ever reported it.

Same bug in ChimeraX 1.6, 1.5 and 1.4.

I'll take a look at why the cap update mechanism is missing the level change.

[Tom Goddard]

Fixed in 1.8 daily, not in 1.7.1.

The volume surface gets recomputed only when it is drawn. But the clip caps are recalculated if the scene geometry has changed before the scene is drawn. So it misses updates of volume surface shape. I fixed this by adding a recalculate_clip_cap attribute to the View class so the shape change from the volume is not missed.