#dehomonogizes a vector
def dehom(v):
    ret = Vector(v[0]/v[3],v[1]/v[3],v[2]/v[3])
    return ret

#takes the inverse of a matrix and returns it
def inverseMatrix(m):
    ret = Matrix([0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0])
    det = m.determinant()

    for i in range(4):
        for j in range(4):
            temp = Matrix([0,0,0],[0,0,0],[0,0,0])
            col = 0
            for x in range(4):
                if x != i:
                    row = 0
                    for y in range(4):
                        if y != j:
                            temp[col][row] = m[x][y]
                            row = row +1
                    col = col +1
            tdet = temp.determinant()
            total = i+j
            if (total % 2):
                sign = -1
            else:
                sign = 1
                
            #i and j are flipped
            ret[j][i] = (sign * tdet) / det
    return ret

#grabs the depth of a pixel from a depth buffer
def getPixelDepth(x,y):


    z = BGL.Buffer(BGL.GL_FLOAT, [1])

    glReadPixels (x,y, 1, 1,
              GL_DEPTH_COMPONENT, GL_FLOAT, z);

    print "value from depth buffer is",z
    return z[0]

#screen_x and screen_y are from Window.GetMouseCoords()
#screen_z is from a call to getPixelDepth(screen_x,screen_y)
def transSC2WC(screen_x,screen_y,screen_z):

  found = 0;
  #clip taken from letter rips code
  for win3d in Window.GetScreenInfo(Window.Types.VIEW3D):
      # we search all 3dwins for the one containing the point
      #(screen_x, screen_y) (could be the mousecoords for example) 
      win_min_x, win_min_y, win_max_x, win_max_y = win3d['vertices']
      # calculate a few geometric extents for this window
      
      mid_x = (win_max_x + win_min_x)/2.0
      mid_y = (win_max_y + win_min_y)/2.0
      width = (win_max_x - win_min_x + 1.0)
      height = (win_max_y - win_min_y + 1.0)
      
      # check if screencoords (screen_x, screen_y) are within the 3dwin 
      if (win_max_x > screen_x > win_min_x) and (  win_max_y > screen_y > win_min_y):
          found = 1
          break
  if(not found):
      print "Not Found!"
      return 0, 0, 0


  coords = Vector( 2* ( screen_x - mid_x)/ width,
        2*(screen_y - mid_y)/height,
        2*screen_z - 1,         
        1.0)

  persp = Window.GetPerspMatrix()
  invpersp = inverseMatrix(persp)

  newcoords = coords*invpersp 
  newcoords = dehom(newcoords)

  return newcoords

# SPACEHANDLER.VIEW3D.EVENT

import Blender
from Blender import *
from Blender.Window import *

evt = Blender.event

def transSC2WC(screen_x,screen_y):
  found = 0;
  #clip taken from letter rips code
  for win3d in GetScreenInfo(Types.VIEW3D):
      win_min_x, win_min_y, win_max_x, win_max_y = win3d['vertices']
      
      mid_x = (win_max_x + win_min_x)/2.0
      mid_y = (win_max_y + win_min_y)/2.0
      width = (win_max_x - win_min_x + 1.0)
      height = (win_max_y - win_min_y + 1.0)
      
      # check if screencoords (screen_x, screen_y) are within the 3dwin 
      if (win_max_x > screen_x > win_min_x) and (  win_max_y > screen_y > win_min_y):
          found = 1
          break
  if(not found):
      return 0, 0, 0

  coords = Mathutils.Vector( 2* ( screen_x - mid_x)/ width,
        2*(screen_y - mid_y)/height,
        .0,
        1.0)

  persp = GetPerspMatrix().invert()
  co = coords*persp
  co = Mathutils.Vector(co[0]/co[3],co[1]/co[3],co[2]/co[3])
  return co

if evt == Draw.LEFTMOUSE:
	mc=GetMouseCoords()
	o=Object.New('Empty')
	o.setLocation(transSC2WC(mc[0],mc[1]))
	Scene.GetCurrent().link(o)
	Redraw()