"Bill Pragnell" <bil### [at] hotmailcom> wrote in message 
news:web.44759ba38c28dbe6731f01d10@news.povray.org...
> Following a problem I had with slow mesh parsing (see povray.general), 
> here
> is my solution, with an example pic, using an optimized mesh2 object.
>
> My goal was to create a fairly good mountain landscape for use in
> backgrounds, etc, without resorting to fiddling with image heightfields or
> waiting for isosurfaces. So this is a heightfield generated using only 
> SDL,
> using an 'envelope' function to control the height of mountains generated
> from pigment functions. I've included the complete scene, with some brief
> comments - hopefully someone will find it useful! I'm using 1 pov-unit = 1
> metre, approximately, so by all means have a play with the numbers.
>
> Bill
>

It's always a good exercise to write a mesh2 generator in POV SDL to better 
understand both the programming and mesh2 formats.  Good work.  A couple 
hints for you here:

1) changing both SineEdge and LandHeight to functions rather than macros 
adds speed.  Parse time dropped from about 90secs to 60secs for me:

#declare SineEdge2 = function 
(xp){select(xp,select(xp+pi,0,0.5*cos(xp)+0.5),1)}
#declare LandHeight2=function 
(xp,yp){SineEdge2(xp+6)*(0.5*land1((xp+hilloff)/sc1, 0, yp/sc1).x + 
0.5*land2((xp+hilloff)/sc2, 0, yp/sc2).x)}

2) There is the function pattern for height_fields which does pretty much 
what you did by hand only much faster (drops down to a mere 6sec parse time, 
plus smoothing can be added):

#macro Region2(xs, ys, maxh, dx)
height_field {
  #local m=(2*xs/dx+2);
  #local n=(2*ys/dx+2);
  function m,n {pattern{function{LandHeight2( (x)*2*xs-xs 
, -((y-1/n)*2*ys-ys) )}}}
  //smooth
  translate <-1/2,0,-1/2>
  scale <2*xs,maxh,2*ys>
  texture { t1 scale maxh }
  texture { t2 scale maxh }
}
#end

Good work on weeding through the math involved in mesh creation though.  I 
did it once for a moebius generator and it was quite educational.  (You 
forgot the smoothing normals though! And uv mapping support!)

-tgq

Post a reply to this message