utility.py

from OpenGL.GL import *
from time import time
import math

import numpy as np
from numpy import linalg as LA

# Provide a terse way to get a uniform location from its name
def U(name):
    p = glGetIntegerv(GL_CURRENT_PROGRAM)
    return glGetUniformLocation(p, name)

# Provide a terse way to create a f32 numpy 3-tuple
def V3(x, y, z):
    return np.array([x, y, z], 'f')

def translation(direction):
    M = np.identity(4)
    M[:3, 3] = direction[:3]
    return M

def look_at(eye, target, up):
    F = target[:3] - eye[:3]
    f = F / LA.norm(F)
    U = up / LA.norm(up)
    s = np.cross(f, U)
    u = np.cross(s, f)
    M = np.identity(4)
    M[:3,:3] = np.vstack([s,u,-f])
    T = translation(-eye)
    return np.array(M * T, 'f')

def perspective(fovy, aspect, f, n):
    s = 1.0/math.tan(math.radians(fovy)/2.0)
    sx, sy = s / aspect, s
    zz = (f+n)/(n-f)
    zw = 2*f*n/(n-f)
    m = np.array([[sx,0,0,0],
                   [0,sy,0,0],
                   [0,0,zz,zw],
                   [0,0,-1,0]], 'f')
    return m