Re: [HACKERS] One more globe

Bruce Momjian wrote:

> >     Well  -  you  wanted  mountains - there they are (Example 2).
> >     But please don't tell me next you want  planes  in  the  air,
> >     smog over NY and dolphins in the sea :-)
>
> Jan, is there no limit to what you can do?

    Rayshade has no wireframe objects like POVray. A wireframe is
    an elegant way to describe complex things like  e.g.  screws.
    In  rayshade  you  have only some primitves like sphere, box,
    cone, cylinder and some flat things like triangle,  disc  and
    polygon.  The  problem with missing wireframes is that things
    like characters are really hard to define.

    Anything to build must be described as combinations  of  such
    primitive  objects. This process is called Constructive Solid
    Geometry (CSG). For example to make a hole in a wall you take
    a  box  and  scale  it to 5.0, 0.2, 3.0 (x,y,z). Now you take
    another box, scale it to 1.0, 0.21,  0.5  move  it  into  the
    center  and  subtract it from the wall. There is now the hole
    where you can put in the window.  If  you  build  four  walls
    don't forget the hole for the door :-)

    Another powerful primitive is the heightfield (what I've used
    to build the mountains on the map). It uses a special file of
    raw  floating  point  values  that describe the altitude of a
    point on a square plane. I've used the etopo5 topography data
    (altitudes  in  meters  for  every  5  minutes  of the earth,
    4320x2160 points though)  and  converted  that  into  such  a
    heightfield  plus  a  color  image  ranging from deep blue at
    ocean bottom to white on the altitude of the himalaya.

    Look here for some other examples what's possible with  these
    few features:

    http://www-graphics.stanford.edu/~cek/rayshade/gallery/gallery.html

    My  favorites  are Chem, Trees, Magic Chain and of course the
    scenes from Nathan Obrien! The  final  PostgreSQL  developers
    globe might be another candidate for the gallery :-)


Jan

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