render to an ms fbo and blit

pygl-ms-fbo.py

# render to an ms fbo and blit

from ctypes import *
import sys

gl = cdll.LoadLibrary('libGL.so')
 
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
 
glCreateShader = gl.glCreateShader
glShaderSource = gl.glShaderSource
glShaderSource.argtypes = [c_int, c_int, POINTER(c_char_p), POINTER(c_int)]
glCompileShader = gl.glCompileShader
glGetShaderiv = gl.glGetShaderiv
glGetShaderiv.argtypes = [c_int, c_int, POINTER(c_int)]
glGetShaderInfoLog = gl.glGetShaderInfoLog
glGetShaderInfoLog.argtypes = [c_int, c_int, POINTER(c_int), c_char_p]
glDeleteShader = gl.glDeleteShader
glCreateProgram = gl.glCreateProgram
glAttachShader = gl.glAttachShader
glLinkProgram = gl.glLinkProgram
glGetError = gl.glGetError
glUseProgram = gl.glUseProgram

GL_FRAGMENT_SHADER = 0x8B30
GL_VERTEX_SHADER = 0x8B31
GL_COMPILE_STATUS = 0x8B81
GL_LINK_STATUS = 0x8B82
GL_INFO_LOG_LENGTH = 0x8B84
 
def compile_shader(source, shader_type):
    shader = glCreateShader(shader_type)
    source = c_char_p(source)
    length = c_int(-1)
    glShaderSource(shader, 1, byref(source), byref(length))
    glCompileShader(shader)
    
    status = c_int()
    glGetShaderiv(shader, GL_COMPILE_STATUS, byref(status))
    if not status.value:
        print_log(shader)
        glDeleteShader(shader)
        raise ValueError, 'Shader compilation failed'
    return shader
 
def compile_program(vertex_source, fragment_source):
    vertex_shader = None
    fragment_shader = None
    program = glCreateProgram()
 
    if vertex_source:
        vertex_shader = compile_shader(vertex_source, GL_VERTEX_SHADER)
        glAttachShader(program, vertex_shader)
    if fragment_source:
        fragment_shader = compile_shader(fragment_source, GL_FRAGMENT_SHADER)
        glAttachShader(program, fragment_shader)
 
    glLinkProgram(program)
 
    if vertex_shader:
        glDeleteShader(vertex_shader)
    if fragment_shader:
        glDeleteShader(fragment_shader)
 
    return program
 
def print_log(shader):
    length = c_int()
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, byref(length))
 
    if length.value > 0:
        log = create_string_buffer(length.value)
        glGetShaderInfoLog(shader, length, byref(length), log)
        print >> sys.stderr, log.value

width, height = 400, 200
def show():
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    program = compile_program('''
    attribute vec4 aPostion;
    
    void main() {
        gl_Position = aPostion;
    }
    ''', '''
    void main() {
	gl_FragColor.rb = gl_FragCoord.xy / vec2(400.0, 200.0);
	gl_FragColor.ga = vec2(0.0, 1.0);
    }
    ''')
    
    vertices = [
			#-0.5, -0.75, 0.0,
			 -0.75, 0.0, 0.0,
			 0,  -0.75, 0.0,
			 0.5,  0.5, 0.0 ]
    vertices2 = [
			-1, -1, 0.0,
			 1, -1, 0.0,
			-1,  1, 0.0,
			 1,  1, 0.0 ]
    
    glViewport(0, 0, width, height)
    glUseProgram(program)    
    
    fbo = glGenFramebuffers(1)
    fbotex = glGenTextures(1)

    glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, fbotex)

    glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, 2, GL_RGBA, width, height, 1)

    glBindFramebuffer(GL_FRAMEBUFFER, fbo)
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_MULTISAMPLE, fbotex, 0)

    glViewport(0, 0, width, height)

    glClearColor(0.3125, 0.3125, 0.3125, 1);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, vertices)
    glEnableVertexAttribArray(0)

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 3)

    glBindFramebuffer(GL_FRAMEBUFFER, 0)
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0)
    glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo)

    glBlitFramebuffer(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST)

    glutSwapBuffers()

if __name__ == '__main__':
    glutInit(sys.argv)
    
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE)

    glutInitWindowSize(width, height)

    glutCreateWindow('MSAA_GL')

    glutDisplayFunc(show)

    glutMainLoop()