from OpenGL.GLUT import *
from PyOSG import osg
from PyOSG import osgUtil
from PyOSG import osgDB

from math import sin, cos
import sys

sceneView = osgUtil.SceneView()
start_tick =  0
frameNum = 0
lastx = 0
lasty = 0
centerPos = osg.Vec3()

viewRot = 0
viewElev = 0
viewRadius = 0

def display():
    global frameNum, viewRadius, viewElev, viewRot, centerPos, lastx, lasty
    # set up the frame stamp for current frame to record the current time and frame number so that animtion code can advance correctly
    frameStamp = osg.FrameStamp()
    frameStamp.setReferenceTime(osg.Timer.instance().delta_s(start_tick,osg.Timer.instance().tick()))
    frameStamp.setFrameNumber( frameNum )
    frameNum += 1

    # pass frame stamp to the SceneView so that the update, cull and draw traversals all use the same FrameStamp
    sceneView.setFrameStamp( frameStamp )

    # set the view
    viewPos = osg.Vec3(\
        viewRadius * cos(viewElev) * sin(viewRot),\
        viewRadius * cos(viewElev) * cos(viewRot),\
        viewRadius * sin(viewElev))
    sceneView.setViewMatrixAsLookAt( centerPos-viewPos, centerPos, osg.Vec3(0.0,0.0,1.0) )

    # do the update traversal the scene graph - such as updating animations
    sceneView.update()

    # do the cull traversal, collect all objects in the view frustum into a sorted set of rendering bins
    sceneView.cull()

    # draw the rendering bins.
    sceneView.draw()

    # Swap Buffers
    glutSwapBuffers()
    glutPostRedisplay()

def reshape( w,  h ):
    # update the viewport dimensions, in case the window has been resized.
    print "Reshaping viewport: ", w, h
    sceneView.setViewport( 0, 0, w, h )

def mousedown( button, state,  x,  y ):
    global lastx, lasty
    lastx = x
    lasty = y

def mousemove(x, y ):
    global viewRot, viewElev, lastx, lasty
    viewRot  += (x - lastx) / 100.0
    viewElev -= (y - lasty) / 100.0

    if( viewElev < -1.5 ): viewElev = -1.5
    if( viewElev >  1.5 ): viewElev =  1.5

    lastx = x
    lasty = y

def keyboard(key, x, y ):
    global viewRot, viewElev
    if key == chr(27):
            sys.exit(0)
    elif key == ' ':
            viewRot = 0.0
            viewElev = 0.0

def menu(selection ):
    print "menu selection = ", selection

def main( argv ):
    global frameNum, viewRadius, viewElev, viewRot, centerPos, lastx, lasty, start_tick, sceneView
    glutInit(argv)

    if len(argv)<2:
        print  argv[0], ": requires filename argument.\n"
        return 1

    # load the scene.
    loadedModel = osgDB.readNodeFile(argv[1])
    if not loadedModel:
        print  argv[0], ": No data loaded.\n"
        return 1

    glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_ALPHA )
    glutInitWindowPosition( 100, 100 )
    glutInitWindowSize( 800, 600 )
    glutCreateWindow( argv[0] )
    glutDisplayFunc( display )
    glutReshapeFunc( reshape )
    glutMouseFunc( mousedown )
    glutMotionFunc( mousemove )
    glutKeyboardFunc( keyboard )

    glutCreateMenu( menu )
    glutAddMenuEntry( "item 0", 0 )
    glutAddMenuEntry( "item 1", 1 )
    glutAttachMenu( GLUT_RIGHT_BUTTON )

    # create the view of the scene.
    sceneView.setDefaults()
    sceneView.setSceneData(loadedModel)

    # initialize the view to look at the center of the scene graph
    bs = loadedModel.getBound()
    centerPos = bs.center()
    viewRot = 0.0
    viewElev = 0.0
    viewRadius = 2.0 * bs.radius()

    # record the timer tick at the start of rendering.
    start_tick = osg.Timer.instance().tick()
    frameNum = 0

    glutMainLoop()
    return 0

if __name__ == "__main__":
    main(sys.argv)