All I can say offhand is "hmmmm",
and "well, lets see...".
In the mean time, to sort out how the i_dat3d functions work, I suggest
comparing y-f(x,z)=0 isofunction tracings to the results of writing the same
f(x,z) values (over a 2d lattice) to a file and using the file in data_2d_3.

"janger" <d_j### [at] hotmailcom> wrote in message
news:3a049f97@news.povray.org...
> Anyone know how to make heightfields using the data_2d functions of
MegaPov?
> Here is a cut from one of David Sharps posts to another confused person:
>
> (how data is written to file)
> <<<<<<<<<<<<<<<<<<<<<<<<<<
> for x=1 to L0
>     for y=1 to L1
>         for z=1 to L2
>               print_to_file( function(x,y,z))
>       next z
>     next y
> next x
>
> Here,  function(x,y,z) is supposed to represent the
> value of the function at the point x,y,z
> >>>>>>>>>>>>>>>>>>>>>>>>>
>
> Now, this is a 3d 'example', but I take this to mean the data maps an
> isosurface where all the data points lie in the range <1,1,1> to
<L0,L1,L2>.
> This just doesn't seem to be the case in practice (not to me, anyway :).
> This also seems to be the opposite of what's stated in the megapov help
file
> (I mean the x,y,z ordering of the data).
>
> All I want to do is make 'heightfields' using the 2d equiv. functions. I
> realise I could convert my data to a tga and make a normal heightfield. My
> reasons for not doing this are for a program I want to write. For the 2d
> case, your manual section in the MegaPov html help says the y-sample
> parameter is ignored. OK, does this mean that:
> <3,1,3,0> will give the same results as <3,2,3,0> or <3,10e34,3,0> or
> whatever L1 is set to?
>
> Do all these example param. vectors mean the data_2d functions expect
3*3=9
> values?
>
> Where in 3d space are these 9 values mapped?
>
> I thought the values were supposed to stand for values as would be
obtained
> by an equivalent iso-function. Does this mean that if my isosurface was
> computed with a threshold of 2, any data-values equal to 2 would lie on
the
> isosurface?
>
> I would appreciate any help, guidance, tutorials, links, criticism;
anything
> that will show me how to do this, or why I should give up on the idea :)
>
> Thanx,
> Dave
>
>

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