#!/usr/bin/env python
from PyOSG import *
from OpenGL.GL import *
from math import sin, cos

import random

RAND_MAX = 1.0
rand = random.random

def makeGalaxy(nvertices):
    geode = osg.Geode()
    galaxy = osg.Geometry()
    vertices = osg.Vec3Array()
    colors = osg.Vec4Array()
    ini = osg.Vec4(1,1,0,1)
    fin = osg.Vec4(0,0,1,1)

    # /** Formula for the two spirals */
    for i in range(nvertices/2):
        val = i*2/float(nvertices) * 2 * 3.14159265359
        modx1 = rand() / RAND_MAX*2
        mody1 = rand() / RAND_MAX*2
        modx2 = rand() / RAND_MAX*2
        mody2 = rand() / RAND_MAX*2
        modz1 = ((rand()-RAND_MAX/2) / RAND_MAX)*3/(val+1)
        modz2 = ((rand()-RAND_MAX/2) / RAND_MAX)*3/(val+1)
        vertices.push_back(osg.Vec3(cos(val)*val+modx1, sin(val)*val+mody1, modz1))
        vertices.push_back(osg.Vec3(-cos(val)*val+modx2, -sin(val)*val+mody2, modz2))

        colors.push_back(ini+(fin-ini)*(i*2.0/nvertices))
        colors.push_back(ini+(fin-ini)*(i*2.0/nvertices))

    galaxy.setVertexArray(vertices)
    galaxy.setColorArray(colors)
    galaxy.setColorBinding(osg.Geometry.BIND_PER_VERTEX)
    galaxy.addPrimitiveSet(osg.DrawArrays(osg.PrimitiveSet.POINTS, 0, nvertices))
    geode.addDrawable(galaxy)
    return geode

def makeStateSet(size):
    set = osg.StateSet()

    # Setup cool blending
    set.setMode(GL_BLEND, osg.StateAttribute.ON)
    fn = osg.BlendFunc()
    fn.setFunction(osg.BlendFunc.SRC_ALPHA, osg.BlendFunc.DST_ALPHA)
    set.setAttributeAndModes(fn, osg.StateAttribute.ON)

    # Setup the point sprites
    sprite = osg.PointSprite()
    set.setTextureAttributeAndModes(0, sprite, osg.StateAttribute.ON)

    # Give some size to the points to be able to see the sprite
    point = osg.Point()
    point.setSize(size)
    set.setAttribute(point)

    # Disable depth test to avoid sort problems and Lighting
    set.setMode(GL_DEPTH_TEST, osg.StateAttribute.OFF)
    set.setMode(GL_LIGHTING, osg.StateAttribute.OFF)

    # The texture for the sprites
    tex = osg.Texture2D()
    tex.setImage(osgDB.readImageFile("Images/particle.rgb"))
    set.setTextureAttributeAndModes(0, tex, osg.StateAttribute.ON)

    return set

def main():
    viewer = osgProducer.Viewer()

    # Make the galaxy of points
    node = makeGalaxy(5000)

    node.setStateSet(makeStateSet(10.0))

    viewer.setUpViewer(osgProducer.Viewer.STANDARD_SETTINGS)
    viewer.setSceneData(node)

    viewer.realize()
    while not viewer.done():
        viewer.sync()
        viewer.update()
        viewer.frame()

    return

if __name__ == "__main__":
    main()