oglcube.py

# Pygame/PyopenGL example by Bastiaan Zapf, Apr 2009
#
# Draw a range of cubes, light them prettily
#
# Employed techniques: 
#
# - Vertex and Fragment shaders
# - Lightsource variables
# - Display Lists


from OpenGL.GL import *
from OpenGL.GLU import *
import random
from math import *  # trigonometry

import pygame  # just to get a display

# import Image
import sys
import time

# get an OpenGL surface

pygame.init()
pygame.display.set_mode((800, 600), pygame.OPENGL | pygame.DOUBLEBUF)

# def jpg_file_write(name, number, data):
#    im = Image.frombuffer("RGBA", (800,600), data, "raw", "RGBA", 0, 0)
#    fnumber = "%05d" % number
#    im.save(name + fnumber + ".jpg")


glEnable(GL_DEPTH_TEST)


# Create and Compile a shader
# but fail with a meaningful message if something goes wrong

def createAndCompileShader(type, source):
    return
    #shader = glCreateShader(type)
    #glShaderSource(shader, source)
    #glCompileShader(shader)

    # get "compile status" - glCompileShader will not fail with 
    # an exception in case of syntax errors

    #result = glGetShaderiv(shader, GL_COMPILE_STATUS)

    #if (result != 1):  # shader didn't compile
    #    raise Exception("Couldn't compile shader\nShader compilation Log:\n".format(glGetShaderInfoLog(shader)))
    #return shader


# Create and Compile fragment and vertex shaders
# Transfer data from fragment to vertex shader

vertex_shader = createAndCompileShader(GL_VERTEX_SHADER, """
varying vec3 v;
varying vec3 N;

void main(void)
{

   v = gl_ModelViewMatrix * gl_Vertex;
   N = gl_NormalMatrix * gl_Normal;

   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

}
""");

fragment_shader = createAndCompileShader(GL_FRAGMENT_SHADER, """
varying vec3 N;
varying vec3 v;

void main(void)
{
   vec3 L = gl_LightSource[0].position.xyz-v;

   // "Lambert's law"? (see notes)
   // Rather: faces will appear dimmer when struck in an acute angle
   // distance attenuation

   float Idiff = max(dot(normalize(L),N),0.0)*pow(length(L),-2.0); 

   gl_FragColor = vec4(0.5,0,0.5,1.0)+ // purple
                  vec4(1.0,1.0,1.0,1.0)*Idiff; // diffuse reflection
}
""");

# build shader program

program = glCreateProgram()
glAttachShader(program, vertex_shader)
glAttachShader(program, fragment_shader)
glLinkProgram(program)

# try to activate/enable shader program
# handle errors wisely

try:
    glUseProgram(program)
except OpenGL.error.GLError:
    print(glGetProgramInfoLog(program))
    raise

done = False

t = 0

# load a cube into a display list

glNewList(1, GL_COMPILE)

glBegin(GL_QUADS)

glColor3f(1, 1, 1)

glNormal3f(0, 0, -1)
glVertex3f(-1, -1, -1)
glVertex3f(1, -1, -1)
glVertex3f(1, 1, -1)
glVertex3f(-1, 1, -1)

glNormal3f(0, 0, 1)
glVertex3f(-1, -1, 1)
glVertex3f(1, -1, 1)
glVertex3f(1, 1, 1)
glVertex3f(-1, 1, 1)

glNormal3f(0, -1, 0)
glVertex3f(-1, -1, -1)
glVertex3f(1, -1, -1)
glVertex3f(1, -1, 1)
glVertex3f(-1, -1, 1)

glNormal3f(0, 1, 0)
glVertex3f(-1, 1, -1)
glVertex3f(1, 1, -1)
glVertex3f(1, 1, 1)
glVertex3f(-1, 1, 1)

glNormal3f(-1, 0, 0)
glVertex3f(-1, -1, -1)
glVertex3f(-1, 1, -1)
glVertex3f(-1, 1, 1)
glVertex3f(-1, -1, 1)

glNormal3f(1, 0, 0)
glVertex3f(1, -1, -1)
glVertex3f(1, 1, -1)
glVertex3f(1, 1, 1)
glVertex3f(1, -1, 1)

glEnd()
glEndList()

while not done:

    t = t + 1

    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(90, 1, 0.01, 1000)
    gluLookAt(sin(t / 260.0) * 4, cos(t / 260.0) * 4, cos(t / 687.0) * 3, 0, 0, 0, 0, 1, 0)

    glClearColor(0.0, 0.0, 0.0, 1.0)
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)

    glMatrixMode(GL_MODELVIEW)

    # calculate light source position

    ld = [sin(t / 16.0) * 4.0, sin(t / 20.0) * 4.0, cos(t / 16.0) * 4.0]

    # pass data to fragment shader

    glLightfv(GL_LIGHT0, GL_POSITION, [ld[0], ld[1], ld[2]]);

    # fallback

    glColor3f(1, 1, 1)

    glLoadIdentity()
    # render a pretty range of cubes

    for i in range(-5, 5):
        for j in range(-5, 5):
            for k in range(-5, 5):
                glPushMatrix()

                glTranslate(i, j, k)
                glScale(0.1, 0.1, 0.1)
                glCallList(1)
                glPopMatrix()

    pygame.display.flip()