projects a 3d point onto the screen

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    sync on
hide mouse

null = make vector3(1)
null = make vector3(2)
null = make matrix4(3) : projection matrix4 3
null = make matrix4(4) : view matrix4 4
null = make matrix4(5) : world matrix4 5


rem just to give some 3d visual reference
make object cube 1,20
position object 1,40,0,350

make matrix 1,1000,1000,30,30

do

   project3dTo2d(1,40,0,350)

   view matrix4 4
   project vector3 1,2,3,4,5

   gosub camera_stuff

   circle x vector3(1),y vector3(1),5
sync
loop


function project3dTo2d(result as integer,x as float, y as float, z as float)
   set vector3 2,x,y,z
   view matrix4 4
   project vector3 1,2,3,4,5
endfunction



camera_stuff:
  oldcx#=cx#
  oldcz#=cz#
  speed# = 5
  if upkey()=1
    cx#=newxvalue(cx#,a#,speed#)
    cz#=newzvalue(cz#,a#,speed#)
  endif
  if downkey()=1
    cx#=newxvalue(cx#,a#,-speed#)
    cz#=newzvalue(cz#,a#,-speed#)
  endif
  if leftkey()=1
    cx#=newxvalue(cx#,wrapvalue(a#-90.0),speed#)
    cz#=newzvalue(cz#,wrapvalue(a#-90.0),speed#)
  endif
  if rightkey()=1
    cx#=newxvalue(cx#,wrapvalue(a#+90.0),speed#)
    cz#=newzvalue(cz#,wrapvalue(a#+90.0),speed#)
  endif

   if shiftkey() then inc cy#, 2
   if controlkey() then dec cy#, 2



  a#=wrapvalue(a#+(mousemovex()/3.0))
  cxa#=cxa#+(mousemovey()/3.0)
  if cxa#<-90.0 then cxa#=-90.0
  if cxa#>90.0 then cxa#=90.0
  cy# = 0
  position camera cx#,cy#+100,cz#
  rotate camera wrapvalue(cxa#),a#,0
RETURN