Making shaders work for both ATI and NVIDIA in Blender Game Engine

Question

Unfortunately coding OpenGL shaders is more strict for ATI cards. I am trying to get this code from this thread http://blenderartists.org/forum/showthread.php?245954-preethams-sky-impementation-HDR to work on my ATI card. Any ideas?

I've even looked into a GPU shader analyzer to try and debug it with no luck http://developer.amd.com/tools/shade...s/default.aspx

When I run the game the flashes blue then the screen is completely white. I am running Blender 2.36a on a ATI 6750

from bge import logic as g
from bge import render as r
from mathutils import *
from math import *
import bgl

cont = g.getCurrentController()
own = cont.owner
scene = g.getCurrentScene()
objects = scene.objects

width = r.getWindowWidth()
height = r.getWindowHeight()

rf = g.getRandomFloat

viewport = bgl.Buffer(bgl.GL_INT, 4)
bgl.glGetIntegerv(bgl.GL_VIEWPORT, viewport);
pixels = bgl.Buffer(bgl.GL_FLOAT, [1])

SAMPLES = 25
ADAPT = 0.99
g.xpoint = []
g.ypoint = []


def init():

    #http://www.cgafaq.info/wiki/Evenly_distributed_points_on_sphere

    dlong = pi*(3-sqrt(5))
    dz = 1.0/SAMPLES
    long = 0
    z = 1 - dz/2

    for i in range(SAMPLES):

        g.xpoint.append([])
        g.ypoint.append([])

        r = sqrt(1-z)

        g.xpoint[i] = viewport[0] + ((cos(long)*r)*0.5+0.5)*width
        g.ypoint[i] = viewport[1] + ((sin(long)*r)*0.5+0.5)*height

        z = z - dz
        long = long + dlong   

    g.reileigh = 1.0
    g.turbidity = 1.5
    g.worldscale = 8.0

    g.contrast = 7.0
    g.bias = 1.2
    g.lumamount = 0.3

    g.initialized = 1



def getlum():

    g.readL = 0
    if hasattr(g,"initialized"):
        for j in range(SAMPLES):
            bgl.glReadPixels(int(g.xpoint[j]),int(g.ypoint[j]), 1, 1, bgl.GL_LUMINANCE, bgl.GL_FLOAT, pixels)
            g.readL += pixels[0]            
    g.readL /= SAMPLES

def setlum():

    Lum = g.readL
    own["L"] = (own["L"]*ADAPT + Lum*(1.0-ADAPT))
    Lum = own["L"]

    g.luminance = own["L"]

    objects["skybox"].color = [own["L"],1.0,1.0,1.0]
    objects["ground"].color = [own["L"],1.0,1.0,1.0]