Last modified September, 1996 - Armel Le Bail


Generalities, Rendering, Perspective, Colors

VRML produced by STRUVIR is compatible with VRML 1.0 specifications, identified by the first line in .wrl files :
#VRML V1.0 ascii


Two VRML files are produced by STRUVIR, however three rendering possibilities are available :
po.wrl with a polyhedral rendering :
wi.wrl with a wireframe rendering :
Showing po.wrl through the wireframe VRML Viewer option gives a different picture :



About perspective, no VRML viewer allows to change it by a button like the 'lamp' button allows to modify the light. Unfortunately, the default perspective is not always adequate.
Default view of a supraconductor as prepared by STRUVIR on the left and with perspective modified by editing the .wrl file on the right :

The secret is that the following lines have been added (see the VRML 1.0 specification), compare ybapo.wrl and ybapo2.wrl :

    PerspectiveCamera { 
            position 0 10 120 
            heightAngle 0.2


You may play with colors at two independent levels for the HPGL/PS outputs and VRML/POVray outputs.

For VRML/POVray, twenty colors are available. The choice depends on the atom name order in the datafile.

The following example has 3 different atom-types CO (Co), S and O. They will be attributed colors number 1, 2 and 3 respectively accorfing to a predefined list given below. If polyhedra (octahedra, tetrahedra or 'bizarre') are recognized around CO, they will be drawn with color attributed to CO (not the color attributed to O).

CELL 6.963 7.580 7.470 90. 116.30 90. 
VIEW 0 1 0 
XYZR -0.25 2.25 -0.25 2.25 -0.25 2.25 
OCTA 90 20 2.05 0.25 
TETR 109. 20. 1.5 0.2 
PARA 1 1 1 1 1 1 1 2.6 
CO 1 0.25 0.25 0.0              Color 1  (first atom-type)
S  1 0.0 0.093 0.25             Color 2  (second atom-type)
O  1 0.203 -.017 0.362          Color 3  (third atom-type)
O  2 0.021 0.196 0.104          Color 3  (third atom-type)
O  3 0.0 0.615 0.25             Color 3  (third atom-type)
Changing colors is possible by changing the atoms order. For instance if you want SO4 tetrahedra drawn with color 4, and CoO6 octahedra with color 5, this is possible by :
OA 1 0.203 -.017 0.362          Color 1 
OB 2 0.021 0.196 0.104          Color 2 
OC 3 0.0 0.615 0.25             Color 3 
S  1 0.0 0.093 0.25             Color 4 
CO 1 0.25 0.25 0.0              Color 5
Compare the STRUVIR po.wrl results from files cso4h.dat and cso4h2.dat, here as viewed by VRweb :

It will be difficult, but not impossible to play with more than 5 colors with this example.

And the 20 colors (care no more) are :

                      R   G   B 
1 Blue sky           0.0  1.0  1.0 
2 Green light        0.5  1.5  0.0 
3 Red pyrope         1.0  0.1  0.5 
4 Yellow             1.0  1.0  0.0 
5 Blue grey          0.6  0.6  1.0 
6 Orange             1.0  0.6  0.0 
7 Purple             0.5  0.0  0.5 
8 Brown              0.5  0.3  0.0 
9 Blue-green-dark    0.0  0.5  0.5 
10 Red               1.0  0.0  0.0 
11 Green             0.0  1.0  0.0 
12 Blue              0.0  0.0  1.0 
13 Pink              1.0  0.0  1.0 
14 Red dark          0.5  0.0  0.0 
15 Green dark        0.0  0.5  0.0 
16 Blue night        0.0  0.0  0.5 
17 Red wine          0.5  0.05 0.25 
18 White             1.0  1.0  1.0 
19 Grey              0.5  0.5  0.5 
20 Black             0.0  0.0  0.0
Colors for the HPGL output are those defined by the COLO instruction.


Choosing a VRML Viewer

Due to the non-optimization of the VRML produced by STRUVIR, only a few VRML viewers are recommended here. Essentially, these viewers should enable two-sided polygon lighting. If not, polyhedra may appear as not fully facetted with parts shown in wireframe and the rendering will change according to the orientation. Note that VRML vewers can be standalone (VRweb...) or plugged in a browser (Live3D...). A browser like Netscape 3.0 standard includes yet Live3D. To Microsoft Internet Explorer 3.0, you may add the MS VRML add-in, however IE 3.0 works with Live3D too. On another hand, Netscape 3.0 and IE 3.0 can be configured to call VRweb when a .wrl file is loaded. See the VRML repository browsers/viewers list.

In spite of clear specifications in VRML 1.0, viewers really do not show the same result on your screen. Try your own VRML viewer on the test file below, look inside the source file to understand the test and compare with the following results where two views rotated 180° are shown :

Netscape 3.0 with Live3D (entry view on the left and rotated 180° along y on the right) :
VRweb, automatic mode
VRweb, enabling double-sided polygons :
VRweb, enabling single-sided mode :
GLView :
A STRUVIR VRML file viewed by VRweb, double-sided (left) and single-sided (right)
Live3D working with Microsoft Explorer 3.0 (left)
compared to Live3D working with Netscape 3.0 (right) :

A difference no visible above is that MS IE 3.0 + Live3D works really much faster than Netscape 3.0 + Live3D !

GLview running standalone on the po.wrl file prepared by STRUVIR from abw.dat :

Other VRML viewers results with STRUVIR files (but note that in case of poor results, the fault is not due to the viewer but is due to STRUVIR doing bad VRML, or is due to me not having well understood the viewer commands) :

Conclusion : Live3D, VRweb or GLView (possibly others) will do the job either called by Netscape 3.0 or Microsoft IE 3.0 or running standalone (at least for VRweb and GLview).


Saving 2D Views

All of the above pictures are 2D views saved as .gif files from screen copies at 640x480 monitor resolution. Under Windows 95, screen copy is really easy. The Microsofr Quickres software is useful for a quick change in the resolution:

Of course if you need quality, select your maximum screen resolution. Then push the 'screen copy' keyboard button. The next step depends on which graphics software you possess.

Generally I save the final views in 1280x1024 resolution. Then I paste the result into LView 3.1 or Paint Shop Pro in order to cut useless parts of the screen copy and to add text, axes, labels and so on. Eventually I insert the .gif or .jpg resulting file into MS WORD 6.0 or 7.0 to scale and print a final figure for publication (see one example as gif file). It is possible also to paste directly the screen copy into MS WORD.


Viewer saving possibilities. Few viewers offer intrinsic file saving of the 2D projections :

Screen Capture. In VRML, you depends on the viewer possibilities. The best would be that viewers allow saving vectorized drawings but to my knowledge none has this option up to now. You may instead use the STRUPLO/STRUVIR HPGL or Postscript options with which at least a thousand figures were published in solid state chemistry literature. But these drawings are wireframe only. You may try the POV-Ray option. However using POV-Ray requires some expertize, but high quality results should be obtained as big .tga files.

Now, the quality of the results by screen copy will also depend a lot on your viewer rendering options. The 1280x1024 resolution is sufficient (a minimum) in my opinion but if you have access to 1600x1200 the result may be really nicer. I have attached a zipped file (abw.zip) containing abw.gif and abw.doc (a MS WORD 7 file). They were prepared as following (each step is important, operating system Windows 95):

So, try to print it directly on a laser printer (black and white or color) or a color inkjet with high quality paper (and try to do it yourself from the beginning with abw.dat to see if you obtain a similar result). This is what I call 'just sufficient for publication' and some publishers seem to agree. Of course this opinion is highly subjective (and also the perspective is exaggerated and should be modified as explained above in the tutorial).

You should be able to obtain much better results in 1600x1200 (as an example, look at a polymorph A of zeolite drawing with STRUVIR by G. L. Price). Care to the viewer you choose and to all the steps in manipulating the files. Using another viewer like VRweb or GLview (...), the results may be different.

Best wishes, hope this helps. If yes, give me some feedback, a fortiori if you find a better way.