import viz
import vizact
import vizmat

viz.setMultiSample(4)
viz.fov(60)
viz.go()

import vizinfo
vizinfo.add('Click on an object to track it\nRight click to stop tracking\nPress \'r\' to reset the simulation')

#Declare some constants
NUM_BALLS = 20
BALL_ALPHA = 0.5

#We need to enable physics
viz.phys.enable()

#Add a ground with an infinite collision plane
ground = viz.addChild('ground.osgb')
ground.collidePlane()


target = 0  #The target we are tracking
lockedTarget = 0    #Have we locked onto the target?
currentLook = viz.Vector()  #Our current look vector
lastTick = viz.tick()   #The last update time

#The list of rigid body objects
bodies = []

#Add a bunch of balls to the physics simulation
for x in range(NUM_BALLS):
    #Add the geometric representation of the ball
    ball = viz.addChild('beachball.osgb',cache=viz.CACHE_COPY)
    #Make ball twice as big
    ball.setScale([2,2,2])
    #The balls collision will be represented by a sphere
    ball.collideSphere()
    #Set the alpha value of the ball
    ball.alpha(BALL_ALPHA)
    #Add the ball to the physical objects list
    bodies.append(ball)

#Add a box model
box = viz.addChild('crate.osgb')
#Use the boxes bounding box for collisions
box.collideBox()
#Set the alpha value of the box
box.alpha(BALL_ALPHA)
#Add the box to the list of physical objects
bodies.append(box)

#Move the head position back and up and look at the origin
viz.MainView.setPosition([0,6,-15])
viz.MainView.lookAt([0,0,0])

#This function will reset the physics simulation
def Reset():
    for x,b in enumerate(bodies):
        #Reset the physics of the object (This will zero its velocities and forces)
        b.reset()
        #Translate the object to the proper height
        b.setPosition([vizmat.GetRandom(-0.2,0.2),x*1.5+15,vizmat.GetRandom(-0.2,0.2)])
        #Reset the rotation of the object
        b.setEuler([0,0,0])

Reset()

def mytimer():
    global lastTick, currentLook, lockedTarget
    if target:
        #Calculate elapsed time
        elapsed = viz.tick() - lastTick
        #Create the vector of the targets current position
        dest = viz.Vector(target.getPosition())
        #Create a vector pointing from our current looking position to the new looking position
        newLook = dest - currentLook
        #Calculate the distance between the two positions
        distance = newLook.length()
        #If the distance is small or we are locked on the target then look at it immediately
        if distance < 0.1 or lockedTarget:
            currentLook = dest
            lockedTarget = 1
        else:
            #We are not locked on the target, so we increment our looking position towards the current position of the target
            newLook.setLength(elapsed * distance * 2)
            currentLook += newLook
        #Look at the newly calculated position
        viz.lookAt(currentLook.get())
    #Save the current time
    lastTick = viz.tick()

vizact.ontimer(0, mytimer)


def startTracking():
    global target, lockedTarget, currentLook
    #Find which object the mouse is over
    node = viz.pick()
    #If the mouse is over an object other than the ground, begin tracking it
    if node in bodies:

        #If we were previously tracking an object, restore its alpha value
        if target:
            target.alpha(BALL_ALPHA)
        else:
            #Calculate our current looking position based on the viewers
            #head position and look vector
            headpos = viz.MainView.getPosition()
            ballpos = node.getPosition()
            distance = vizmat.Distance(headpos,ballpos)
            currentLook.set(viz.MainView.getMatrix().getForward())
            currentLook.setLength(distance)
            currentLook += headpos
        #Save the new target and set its alpha
        target = node
        lockedTarget = 0
        target.alpha(1)
        #turn off mouse navigation
        viz.mouse(viz.OFF)


def stopTracking():
    global target, lockedTarget, currentLook
    #Stop tracking the current target and turn on mouse navigation
    if target:
        target.alpha(BALL_ALPHA)
    target = 0
    lockedTarget = 0
    viz.mouse(viz.ON)


vizact.onmousedown(viz.MOUSEBUTTON_LEFT, startTracking)
vizact.onmousedown(viz.MOUSEBUTTON_RIGHT, stopTracking)


#'r' key resets simulation
vizact.onkeydown('r',Reset)

#Set the background color
viz.clearcolor(viz.SKYBLUE)