Hi, 3d plots are the most important missing feature in the goffice charts engine. I intend to work on that now, in the hope it will be ready for goffice-0.4. At first, some questions must be answered before starting real work.
- axes: in 2d plots, length of the axes are just the width and the height of the chart. In 3d plots, the situation is quite different, we must give the axes arbitrary lengths, and then we make a projection so that we fill most of the available place. The question is how should we decide the relative lengths of the three axes. There are probably several available options and we'll have to make them all available to the user. - rendering: should we use opengl or another solution? Some times ago, I was quite reluctant about using opengl because there is no priting support. However, it is still possible to render the chart to a high resolution pixbuf (at 300 dpi or so), and print the pixbuf; it works, but my first tests (in another program) show that even if it does not use much cpu time, it does use a lot of printer time. Also, the appearance should be as near as possible to our 2d charts. If we decide to not use opengl, we can explore what other free software do, and cheat a bit. - orientation of the scene: to position a solid in the space, three angles are needed, and we also need a field of view. Excel, use only two angles for the orientation, and OOoCalc is fully non intuitive for me, and I could not find how things work in there. I have some experience with the use of the so called Euler's angles (and working code), but they are not very intuitive too. IMHO, we should devise a simple widget (based on an opengl sphere) which the user might use to change the orientation, which does not precludes the use of entries for the angles. Waiting for your great ideas about these points, Cheers Jean _______________________________________________ gnumeric-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/gnumeric-list
