horizontal fov

[Andrea Viarengo]

Hi Christian,

Another exercise for you...

I have tried to calculated the horizontal fov:

      width,height = pipmak.screensize()
      vfov_deg = pipmak.getverticalfov()
      vfov_rad = math.rad(vfov_deg)
      distance = (height/2)/math.tan(vfov_rad/2))
      hfov_rad = 2*math.atan((width/2)/distance))
      hfov_deg = math.deg(hfov_rad)

but it's not true, because I get an angle lower than what I can measure.
What I have forgotten?

Thanks

Andrea



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[Christian Walther]

Andrea Viarengo wrote:

> I have tried to calculated the horizontal fov:
>
>       width,height = pipmak.screensize()
>       vfov_deg = pipmak.getverticalfov()
>       vfov_rad = math.rad(vfov_deg)
>       distance = (height/2)/math.tan(vfov_rad/2))
>       hfov_rad = 2*math.atan((width/2)/distance))
>       hfov_deg = math.deg(hfov_rad)
>
> but it's not true, because I get an angle lower than what I can measure.

That looks correct. What does it give you, and what do you measure, and how?

  -Christian


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[Andrea Viarengo]

Hi,

Ok, it's correct, because my formula go well only with elevation=0

I believed to found a formula that permit me to put four patches at four
angles of the field of view, and I expected (wrong) to view these
four images always at the angles of the screen,
but this is true only with elevation=0.

Ok,ok, it's only an accademic discussion...just to learn....

---------------------------------------------------------------------
--
-- calculate and show fov limits
--
---------------------------------------------------------------------ù

side   = pipmak.newimage(512,512):color(0,0,1):fill(0,0,512,256)
         side:color(1,1,1):fill(0,256,512,256)
top    = pipmak.newimage(512,512):color(0,0,1):fill(0,0,512,512)
bottom = pipmak.newimage(512,512):color(1,1,1):fill(0,0,512,512)

cubic {side,side,side,side,top,bottom}

---------------------------------------------------------------------
function setpos(p,dis,az,el)
   local nz = -math.cos(math.rad(az))*math.cos(math.rad(el))
   local nx =  math.sin(math.rad(az))*math.cos(math.rad(el))
   local ny =  math.sin(math.rad(el))
   local dl =  math.deg(math.asin(nx))
   local bz =  math.deg(math.atan2(ny, -nz))
   p:move{nx=nx*dis, ny=ny*dis, nz=nz*dis, anglex=bz, angley=-dl}
end
---------------------------------------------------------------------
function setfovlimits(az,el,di,hdl)
  local width,height = pipmak.screensize()
  local vfov_deg = pipmak.getverticalfov()
  local vfov_rad = math.rad(vfov_deg)
  local distance = (height/2)/math.tan(vfov_rad/2)
  local hfov_rad = 2*math.atan((width/2)/distance)
  local hfov_deg = math.deg(hfov_rad)

  local az_min = az-hfov_deg/2
  local az_max = az+hfov_deg/2
  local el_min = el-vfov_deg/2
  local el_max = el+vfov_deg/2

  hdl:move{az=az_min,el=el_max,w=hfov_deg,h=vfov_deg}

  setpos(p1,di ,az,     el    )
  setpos(p2,di ,az_min, el    )
  setpos(p3,di ,az_max, el    )
  setpos(p4,di ,az,     el_min)
  setpos(p5,di ,az,     el_max)

  pipmak.setviewdirection(az,el)
end
---------------------------------------------------------------------

az = 90
el =  0
di =  4

hdl = handle{az=0,el=0,w=0,h=0}

cross=pipmak.newimage(64,64):fill(30,0,4,64):fill(0,30,64,4)

p1=patch{nx=0,ny=0,nz=0,anchorh=32,anchorv=32,w=64,h=64,image=cross }
p2=patch{nx=0,ny=0,nz=0,anchorh=32,anchorv=32,w=64,h=64,image=cross }
p3=patch{nx=0,ny=0,nz=0,anchorh=32,anchorv=32,w=64,h=64,image=cross }
p4=patch{nx=0,ny=0,nz=0,anchorh=32,anchorv=32,w=64,h=64,image=cross }
p5=patch{nx=0,ny=0,nz=0,anchorh=32,anchorv=32,w=64,h=64,image=cross }

setfovlimits(az,el,di,hdl)
pipmak.setshowcontrols(true)

onkeydown (
    function(key)
      press="no"
      if key == pipmak.key_arrow_up    then press="yes" el=el+10 end
      if key == pipmak.key_arrow_down  then press="yes" el=el-10 end    
      if press=="yes" then
        setfovlimits(az,el,di,hdl)        
        return true
      else
        pipmak_internal.project.onkeydown(key)
        return true
      end
   end
   )

---------------------------------------------------------------------

P.S.: I don't remember anymore why I fell in this.....
      Probably the heat has a bad effect on me....

Bye

-Andrea



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[NigeC]

Andrea Viarengo wrote:

      Probably the heat has a bad effect on me....

come to England, we had our summer for 3 days in May! its been wet, cold, windy ever since