Jmol.___JmolVersion="14.3.13_2015.04.29"
bug fix: perspective renderer was using the wrong formula for calculating Z
depth of pixels:
* Well, it turns out that the calculation of the intermediate pixel z value
* in all methods involving rasterization of lines is incorrect and has been
* incorrect since Jmol's inception. I noticed long ago that large
triangles such as
* produced in DRAW could incorrectly overlay/underlay other objects, but I
could
* never determine why. It turns out that the assumption that z-value is
linear
* across a line when perspectiveDepth is TRUE is simply incorrect.
*
* Basically, the function z(x) is non-linear. Treating it as simply a
* linear function results in oddities where lines and planes
* -- particularly created using DRAW and large distances -- appear
* to be where they are not.
*
* Through Jmol 13.3.13 we had the standard linear relationship:
*
* z = (x - xa) / (xb - xa) * (zb - za) + za
*
* I worked it out, and, amazingly, it should be
*
* z = (xb - xa) * za * zb / ((xb - x) * zb + (x - xa) * za)
*
* Note that it is still true that when x = xb, z = zb
* and when x = xa, z = za, as required.
*
* This equation can be rearranged to
*
* z = a / (b - x)
*
* where
*
* a = (xb - xa) * za * (zb / (zb - za))
*
* and
*
* b = (xb * zb - xa * za) / (zb - za)
*
* These values must be floats, not integers, to work properly, because
* these are extrapolations from long distances in some cases. So there is
* considerable overhead there. It will take some experimentation to figure
this
* out.
*
* The practical implications are for line, cylinder, and triangle drawing.
* First-pass corrections are for axes and DRAW objects. They tend to be the
* larger objects that result in the issue.
*
* Also affected is POV-Ray output, because right now POV-Ray is created
using
* perspective on and plotted as though it were orthographic, but although
that
* works in x and y, it does not work in z!
*
JmolVersion="14.3.13_2015.04.27"
bug fix: with set dragSelected, highlight does not recognize whole molecule
JmolVersion="14.3.13_2015.04.25"
code: integration of changes made for SwingJS into JSmol code
--
Robert M. Hanson
Larson-Anderson Professor of Chemistry
Chair, Department of Chemistry
St. Olaf College
Northfield, MN
http://www.stolaf.edu/people/hansonr
If nature does not answer first what we want,
it is better to take what answer we get.
-- Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900
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