> Agreed. The need for 3D display applet is still very high... > On thursday I had two people over about crystal structure display. There > were basically two things missing: > > 1. building crystals using symmetry operations (space groups) > I've already discussed this with Fabian in the past and I plan to at > least implement this in v7 partially.
CML supports symmetry operators as matrices which can be used for i/o. There needs to be additional specifications of which symmetry operations to apply. This can either be ("all those which generate points within a given parallelepiped" or "those specified by the author". By using the ID of the symops and a translation vector it would be straightforward to specify this:
> 2. Display over isosurfaces, which they need for energy band plotting > I think. > > The latter would be great to have implemented.
Do we know anybody who understands the mathematics behind these isosurfaces?
There is a large public collection of graphics algorithms in "graphics gems", which would be the first place I would look. I don't think they have been translated into Java.
One thing that concerns me about the 3D graphics is that my math may not be strong enough.
For spheres & lines, calculating the 3D projection onto a 2D display is straightforward. A sphere always maps to a circle and the zdepth is easy to calculate, regardless of the orientation.
Bonds are more difficult since they are cylinders. Yesterday I spent 8 hours with a professor of Mathematics at the University of Salamanca. He worked through the equations of the ellipsoid projection of a cylinder onto a 2D plane. Plus derivatives.
I seem to remember these are in GG.
I think I can handle the bonds (cylinders).
But we probably will need to find somebody who has a good understanding of these isosurfaces.
There are many implementations so it should mainly involve gluing the algorithms or recoding them in Java.
P.
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