traceback trying to morph 3 structures (session attached)

[Elaine Meng]

As shown in the Log contents below, with the attached session I can morph #1,​2 and morph #2,​4 but not morph #1,​2,​4

UCSF ChimeraX version: 0.1 (2017-03-31)
OpenGL version: 4.1 NVIDIA-10.14.20 355.10.05.15f03
OpenGL renderer: NVIDIA GeForce GTX 675MX OpenGL Engine
OpenGL vendor: NVIDIA Corporation

open ~/Desktop/movie-project/cx-phyr-temp.cxs
opened ChimeraX session
morph #1,​2
Computed 21 frame morph #5
coordset #5 1,21
close #5
morph #2,​4
Computed 21 frame morph #5
coordset #5 1,21
close #5

morph #1,​2,​4
Traceback (most recent call last):
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/cmd_line/tool.py", line 161, in execute
cmd.run(cmd_text)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/commands/cli.py", line 2327, in run
result = ci.function(session, kw_args)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/morph/morph.py", line 46, in morph
cartesian=cartesian, match_same=same, core_fraction = core_fraction)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/morph/motion.py", line 20, in compute_morph
motion.interpolate(mol, res_interp)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/morph/motion.py", line 118, in interpolate
seg_interp = SegmentInterpolator(res_groups, self.method, coords0, coords1)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/morph/interpolate.py", line 148, in init
axis, angle, center, shift = calc_motion_parameters(xform, c0, c1)
ValueError: not enough values to unpack (expected 4, got 2)

[Tom Goddard]

Fixed.

The morph corkscrew interpolation code caused an error in the rare case when a segment motion was parallel its rotation axis.

The resulting morph looks not too bad.

[Elaine Meng]

Thnaks, the bug/traceback is fixed.  However, I would disagree with “morph looks not too bad”... it looks awful to me.  At least with default settings (corkscrew linear) it’s the same as in Chimera1: during most of the morph between #1 and #2 in the example session, there are ridiculously long covalent bonds between residues 218-219 and 227-228, ~14 and 10 angstroms long (measured in Chimera1).  The second morph to domain-swap the terminal helix also looks extremely unphysical, albeit less strained.

[pett]

Testing if this “reply” gets added to the ticket…

—Eric