GLSL_ARB_Example — wiki

This snippet is derived from the GLSLExample, but uses ARB extensions instead of OpenGL 2.0. This lets those of us with older drivers use nifty shaders too.
from ctypes import *
import sys
 
import pygame
from pygame.locals import *
 
try:
    # For OpenGL-ctypes
    from OpenGL import platform
    gl = platform.OpenGL
except ImportError:
    try:
      # For PyOpenGL
      gl = cdll.LoadLibrary('libGL.so')
    except OSError:
        # Load for Mac
        from ctypes.util import find_library
        path = find_library('OpenGL')    # finds the absolute path to the framework
        gl = cdll.LoadLibrary(path)
 
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *

GL_FRAGMENT_SHADER_ARB = 0x8B30
GL_VERTEX_SHADER_ARB = 0x8B31
GL_OBJECT_COMPILE_STATUS_ARB= 0x8B81
GL_OBJECT_LINK_STATUS_ARB = 0x8B82
GL_INFO_LOG_LENGTH_ARB = 0x8B84


glCreateShaderObjectARB = gl.glCreateShaderObjectARB
glShaderSourceARB = gl.glShaderSourceARB
glShaderSourceARB.argtypes = [c_int, c_int, POINTER(c_char_p), POINTER(c_int)]
glCompileShaderARB = gl.glCompileShaderARB
glGetObjectParameterivARB = gl.glGetObjectParameterivARB
glGetObjectParameterivARB.argtypes = [c_int, c_int, POINTER(c_int)]
glCreateProgramObjectARB = gl.glCreateProgramObjectARB
glGetInfoLogARB = gl.glGetShaderInfoLog
glGetInfoLogARB.argtypes = [c_int, c_int, POINTER(c_int), c_char_p]
glAttachObjectARB = gl.glAttachObjectARB
glLinkProgramARB = gl.glLinkProgramARB
glDeleteObjectARB = gl.glDeleteObjectARB
glGetError = gl.glGetError
glUseProgramObjectARB = gl.glUseProgramObjectARB



        
def print_log(shader):
    length = c_int()
    glGetObjectParameterivARB(shader, GL_INFO_LOG_LENGTH, byref(length))
 
    if length.value &gt; 0:
        log = create_string_buffer(length.value)
        glGetInfoLogARB(shader, length, byref(length), log)
        print &gt;&gt; sys.stderr, log.value

        
        
def compile_shader(source, shader_type):
    shader = glCreateShaderObjectARB(shader_type)
    source = c_char_p(source)
    length = c_int(-1)
    glShaderSourceARB(shader, 1, byref(source), byref(length))
    glCompileShaderARB(shader)
    status = c_int()
    glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB,
        byref(status))
    if (not status.value):
        print_log(shader)
        raise SystemExit
    return shader
    

def compile_program(vertex_source, fragment_source):
    vertex_shader = None
    fragment_shader = None
    program = glCreateProgramObjectARB()
 
    if vertex_source:
        vertex_shader = compile_shader(vertex_source, GL_VERTEX_SHADER_ARB)
        glAttachObjectARB(program, vertex_shader)
    if fragment_source:
        fragment_shader = compile_shader(fragment_source,
            GL_FRAGMENT_SHADER_ARB)
        glAttachObjectARB(program, fragment_shader)
 
    glLinkProgramARB(program)
 
    if vertex_shader:
        glDeleteObjectARB(vertex_shader)
    if fragment_shader:
        glDeleteObjectARB(fragment_shader)
 
    return program
    
    
if __name__ == '__main__':
    glutInit(sys.argv)
    width, height = 640, 480
    pygame.init()
    pygame.display.set_mode((width, height), OPENGL | DOUBLEBUF)
 
    program = compile_program('''
    varying vec3 normal;
    void main() {
        normal = gl_NormalMatrix * gl_Normal;
        gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
    }
    ''', '''
    varying vec3 normal;
    void main() {
        float intensity;
        vec4 color;
        vec3 n = normalize(normal);
        vec3 l = normalize(gl_LightSource[0].position).xyz;
 
        // quantize to 5 steps (0, .25, .5, .75 and 1)
        intensity = (floor(dot(l, n) * 4.0) + 1.0)/4.0;
        color = vec4(intensity*1.0, intensity*0.5, intensity*0.5,
            intensity*1.0);
 
        gl_FragColor = color;
    }
    ''')
 
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(90.0, width/float(height), 1.0, 100.0)
    glMatrixMode(GL_MODELVIEW)
    glEnable(GL_DEPTH_TEST)
    
    quit = False
    angle = 0
    while not quit:
        for e in pygame.event.get():
            if e.type in (QUIT, KEYDOWN):
                quit = True
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
        glLoadIdentity()
        glTranslate(0.0, 0.0, -2.5)
        glRotate(angle, 0.0, 1.0, 0.0)
        glUseProgramObjectARB(program)
        glutSolidTeapot(1.0)
        angle += 0.1 
        pygame.display.flip()
GLSL_ARB_Example — wiki

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