Example of how to leave a footprint on terrain

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    sync on
sync rate 60
autocam off
hide mouse
randomize timer()

`load image "grass.bmp", 1

make matrix 1, 1000, 1000, 40, 40
`prepare matrix texture 1, 1, 1, 1
randomize matrix 1, 200
smooth_matrix(1,2,40,40)
update matrix 1


rem footprint
make object plain 999,10,10
xrotate object 999,270
fix object pivot 999




DO


   gosub camera_stuff


   if spacekey() and flag = 0
      flag = 1
      make_footprint(1, camera position x(),camera position z())
   endif

   if spacekey() = 0 then flag = 0

   sync
LOOP










REM ==========================================================================
REM Parameters:
REM matrix number
REM X coordinate
REM Z coordinate
function make_footprint(number as integer, x# as float, z# as float)
   h1# = get ground height(number, x#, z#)
   h2# = get ground height(number, x#+2, z#)
   a# = h2# - h1#
   b# = 2
   angz# = atan(a#/b#)

   h2# = get ground height(number, x#, z#+2)
   a# = h2# - h1#
   angx# = 360 - atan(a#/b#)

   position object 999, x#, h1#+0.5, z#
   rotate object 999,angx#,0,angz#
endfunction


REM ==========================================================================
REM Parameters:
REM matrix number
REM number of iterations
REM number of X tiles
REM number of Z tiles
function smooth_matrix(number as integer, iter as integer, xsegs as integer, zsegs as integer)

   dim heights#(xsegs, zsegs)

   rem store original heights
   for z = 0 to zsegs
      for x = 0 to xsegs
         heights#(x,z) = get matrix height(number,x,z)
      next x
   next z

   for t = 1 to iter
      for z = 0 to zsegs
         for x = 0 to xsegs
            count = 0
            h1# = 0
            h2# = 0
            h3# = 0
            h4# = 0
            h5# = 0
            h6# = 0
            h7# = 0
            h8# = 0

           if z < zsegs
               if x > 0 then h1# = heights#(x-1,z+1) : inc count
               h2# = heights#(x,z+1) : inc count
               if x < xsegs then h3# = heights#(x+1,z+1) : inc count
            endif

            if x > 0 then h4# = heights#(x-1,z) : inc count
            if x < xsegs then h5# = heights#(x+1,z) : inc count

            if z > 0
               if x > 0 then h6# = heights#(x-1,z-1) : inc count
               h7# = heights#(x,z-1) : inc count
               if x < xsegs then h8# = heights#(x+1,z-1) : inc count
            endif

            avg# = (h1#+h2#+h3#+h4#+h5#+h6#+h7#+h8#) / count

            set matrix height number,x,z,avg#
            heights#(x,z) = avg#

         next x
      next z
   next t

   rem delete array
   undim heights#()

endfunction





camera_stuff:
  oldcx#=cx#
  oldcz#=cz#
  speed# = 5

  if shiftkey() then speed# = 10
  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# = get ground height(1,cx#,cz#)
  position camera cx#,cy#+50,cz#
  rotate camera wrapvalue(cxa#),a#,0
RETURN