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OBJFileLoader

      
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This code provides a function for loading a model from a wavefront OBJ file (3d model format) into an OpenGL display list. It additionally loads any referenced material and texture files. It does not support multiple models in the OBJ file, nor any material properties other than diffuse colour (Kd) and diffuse texture (map_Kd).

TODO:

  1. support more of the OBJ format.
  2. convert to using vertex/normal/color/texture_coord arrays
import pygame
from OpenGL.GL import *
 
def MTL(filename):
    contents = {}
    mtl = None
    for line in open(filename, "r"):
        if line.startswith('#'): continue
        values = line.split()
        if not values: continue
        if values[0] == 'newmtl':
            mtl = contents[values[1]] = {}
        elif mtl is None:
            raise ValueError, "mtl file doesn't start with newmtl stmt"
        elif values[0] == 'map_Kd':
            # load the texture referred to by this declaration
            mtl[values[0]] = values[1]
            surf = pygame.image.load(mtl['map_Kd'])
            image = pygame.image.tostring(surf, 'RGBA', 1)
            ix, iy = surf.get_rect().size
            texid = mtl['texture_Kd'] = glGenTextures(1)
            glBindTexture(GL_TEXTURE_2D, texid)
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                GL_LINEAR)
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
                GL_LINEAR)
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ix, iy, 0, GL_RGBA,
                GL_UNSIGNED_BYTE, image)
        else:
            mtl[values[0]] = map(float, values[1:])
    return contents
 
class OBJ:
    def __init__(self, filename, swapyz=False):
        """Loads a Wavefront OBJ file. """
        self.vertices = []
        self.normals = []
        self.texcoords = []
        self.faces = []
 
        material = None
        for line in open(filename, "r"):
            if line.startswith('#'): continue
            values = line.split()
            if not values: continue
            if values[0] == 'v':
                v = map(float, values[1:4])
                if swapyz:
                    v = v[0], v[2], v[1]
                self.vertices.append(v)
            elif values[0] == 'vn':
                v = map(float, values[1:4])
                if swapyz:
                    v = v[0], v[2], v[1]
                self.normals.append(v)
            elif values[0] == 'vt':
                self.texcoords.append(map(float, values[1:3]))
            elif values[0] in ('usemtl', 'usemat'):
                material = values[1]
            elif values[0] == 'mtllib':
                self.mtl = MTL(values[1])
            elif values[0] == 'f':
                face = []
                texcoords = []
                norms = []
                for v in values[1:]:
                    w = v.split('/')
                    face.append(int(w[0]))
                    if len(w) >= 2 and len(w[1]) > 0:
                        texcoords.append(int(w[1]))
                    else:
                        texcoords.append(0)
                    if len(w) >= 3 and len(w[2]) > 0:
                        norms.append(int(w[2]))
                    else:
                        norms.append(0)
                self.faces.append((face, norms, texcoords, material))
 
        self.gl_list = glGenLists(1)
        glNewList(self.gl_list, GL_COMPILE)
        glEnable(GL_TEXTURE_2D)
        glFrontFace(GL_CCW)
        for face in self.faces:
            vertices, normals, texture_coords, material = face
 
            mtl = self.mtl[material]
            if 'texture_Kd' in mtl:
                # use diffuse texmap
                glBindTexture(GL_TEXTURE_2D, mtl['texture_Kd'])
            else:
                # just use diffuse colour
                glColor(*mtl['Kd'])
 
            glBegin(GL_POLYGON)
            for i in range(len(vertices)):
                if normals[i] > 0:
                    glNormal3fv(self.normals[normals[i] - 1])
                if texture_coords[i] > 0:
                    glTexCoord2fv(self.texcoords[texture_coords[i] - 1])
                glVertex3fv(self.vertices[vertices[i] - 1])
            glEnd()
        glDisable(GL_TEXTURE_2D)
        glEndList()

Sample usage of this code (saving the above as the module "objloader.py" and passing the filename of the obj file to display on the command-line):

# Basic OBJ file viewer. needs objloader from:
#  http://www.pygame.org/wiki/OBJFileLoader
# LMB + move: rotate
# RMB + move: pan
# Scroll wheel: zoom in/out
import sys, pygame
from pygame.locals import *
from pygame.constants import *
from OpenGL.GL import *
from OpenGL.GLU import *
 
# IMPORT OBJECT LOADER
from objloader import *
 
pygame.init()
viewport = (800,600)
hx = viewport[0]/2
hy = viewport[1]/2
srf = pygame.display.set_mode(viewport, OPENGL | DOUBLEBUF)
 
glLightfv(GL_LIGHT0, GL_POSITION,  (-40, 200, 100, 0.0))
glLightfv(GL_LIGHT0, GL_AMBIENT, (0.2, 0.2, 0.2, 1.0))
glLightfv(GL_LIGHT0, GL_DIFFUSE, (0.5, 0.5, 0.5, 1.0))
glEnable(GL_LIGHT0)
glEnable(GL_LIGHTING)
glEnable(GL_COLOR_MATERIAL)
glEnable(GL_DEPTH_TEST)
glShadeModel(GL_SMOOTH)           # most obj files expect to be smooth-shaded
 
# LOAD OBJECT AFTER PYGAME INIT
obj = OBJ(sys.argv[1], swapyz=True)
 
clock = pygame.time.Clock()
 
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
width, height = viewport
gluPerspective(90.0, width/float(height), 1, 100.0)
glEnable(GL_DEPTH_TEST)
glMatrixMode(GL_MODELVIEW)
 
rx, ry = (0,0)
tx, ty = (0,0)
zpos = 5
rotate = move = False
while 1:
    clock.tick(30)
    for e in pygame.event.get():
        if e.type == QUIT:
            sys.exit()
        elif e.type == KEYDOWN and e.key == K_ESCAPE:
            sys.exit()
        elif e.type == MOUSEBUTTONDOWN:
            if e.button == 4: zpos = max(1, zpos-1)
            elif e.button == 5: zpos += 1
            elif e.button == 1: rotate = True
            elif e.button == 3: move = True
        elif e.type == MOUSEBUTTONUP:
            if e.button == 1: rotate = False
            elif e.button == 3: move = False
        elif e.type == MOUSEMOTION:
            i, j = e.rel
            if rotate:
                rx += i
                ry += j
            if move:
                tx += i
                ty -= j
 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glLoadIdentity()
 
    # RENDER OBJECT
    glTranslate(tx/20., ty/20., - zpos)
    glRotate(ry, 1, 0, 0)
    glRotate(rx, 0, 1, 0)
    glCallList(obj.gl_list)
 
    pygame.display.flip()
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