OpenEuphoria

Re: 3D math

• Posted by mwfch at MWEB.CO.ZA Apr 26, 2001
• 649 views

Thanks a lot , that cleard it up a lot !

Read ya later !
Ferdinand Greyling(DukeFungus)

----- Original Message -----
From: Chris Bensler <bensler at mailops.com>
To: <EUforum at topica.com>
Subject: RE: 3D math


> >
>
> Hi Ferdinand,
>
>   Here is how it works.. (I may be mistaken, I haven't done 3d code in a
> while)
>
> You start with your 3d point (X,Y,Z)
>
> the formula for converting to screen coordinates is..
>
>    X = (X * FOV)/Z + (screen_width/2)
>    Y = (Y * FOV)/Z + (screen_height/2)
>
> FOV is the Field Of View, which is just so your 3d objects arent very,
> very small.. Usually FOV is 256 or something close to that. It's up to
> you.
>
> Z is in the range >0 to FOV..
> a big Zvalue is closer , a small Zvalue is farther
>
> make sure you test to make sure Z is never 0, or you will get a divide
> _by_zero error.
>
> I don't understand it very well myself.. I just get it to work and then
> I'm happy . :P
>
> here is some example code in C some docs I have....
> I just draws a dot in 3d
>
> -- EXAMPLE
>    x = 1
>    y = 1
>    z = 256
>    FOV = 256
>    while (gx<320) and (gx>-1) and (gy<200) and (gy>-1)
>       gx = x * FOV / z + 160 ; center = the center of the screen
>       gy = y * FOV / z + 100 ; (mode 320x200)
>       putpixel(gx,gy,15)
>       z = z - 1
>       if (z = 0)
>          z = -1 ; just to ensure...
>       endif
>    endwhile
> -- END of EXAMPLE
>
> NOTE..
> You can get rid of the FOV if Z is in the range 0.1 to 1.0
>
> Hope that helps..
>
<snip>

> >
> >