STLFile.py

from OpenGL.GL import *
from OpenGL.GLU import *
import struct

#class for a 3d point
class createpoint:
    def __init__(self,p,c=(1,0,0)):
        self.point_size=0.5
        self.color=c
        self.x=p[0]
        self.y=p[1]
        self.z=p[2]
      
    def glvertex(self):
        glVertex3f(self.x,self.y,self.z)

#class for a 3d face on a model
class createtriangle:
    points=None
    normal=None

    def __init__(self,p1,p2,p3,n=None):
        #3 points of the triangle
        self.points=createpoint(p1),createpoint(p2),createpoint(p3)
      
        #triangles normal
        self.normal=createpoint(self.calculate_normal(self.points[0],self.points[1],self.points[2]))#(0,1,0)#
  
    #calculate vector / edge
    def calculate_vector(self,p1,p2):
        return -p1.x+p2.x,-p1.y+p2.y,-p1.z+p2.z
      
    def calculate_normal(self,p1,p2,p3):
        a=self.calculate_vector(p3,p2)
        b=self.calculate_vector(p3,p1)
        #calculate the cross product returns a vector
        return self.cross_product(a,b)    
  
    def cross_product(self,p1,p2):
        return (p1[1]*p2[2]-p2[1]*p1[2]) , (p1[2]*p2[0])-(p2[2]*p1[0]) , (p1[0]*p2[1])-(p2[0]*p1[1])

class loader:
    def __init__(self, filename):
        self.model=[]
        self.load_stl(filename)
    #return the faces of the triangles
    def get_triangles(self):
        if self.model:
            for face in self.model:
                yield face

    #draw the models faces
    def draw(self):
        glBegin(GL_TRIANGLES)
        for tri in self.get_triangles():
            glNormal3f(tri.normal.x,tri.normal.y,tri.normal.z)
            glVertex3f(tri.points[0].x,tri.points[0].y,tri.points[0].z)
            glVertex3f(tri.points[1].x,tri.points[1].y,tri.points[1].z)
            glVertex3f(tri.points[2].x,tri.points[2].y,tri.points[2].z)
        glEnd()
  
    #load stl file detects if the file is a text file or binary file
    def load_stl(self,filename):
        #read start of file to determine if its a binay stl file or a ascii stl file
        fp=open(filename,'rb')
        h=fp.read(80)
        type=h[0:5]
        fp.close()
        if type==b'solid':
            # print ("reading stl file "+str(filename))
            self.load_text_stl(filename)
        else:
            # print ("reading binary stl file "+str(filename))
            self.load_binary_stl(filename)
  
    #read text stl match keywords to grab the points to build the model
    def load_text_stl(self,filename):
        fp=open(filename,'r')

        for line in fp.readlines():
            words=line.split()
            if len(words)>0:
                if words[0]=='solid':
                    self.name=words[1]

                if words[0]=='facet':
                    center=[0.0,0.0,0.0]
                    triangle=[]
                    normal=(eval(words[2]),eval(words[3]),eval(words[4]))
                  
                if words[0]=='vertex':
                    triangle.append((eval(words[1]),eval(words[2]),eval(words[3])))
                  
                  
                if words[0]=='endloop':
                    #make sure we got the correct number of values before storing
                    if len(triangle)==3:
                        self.model.append(createtriangle(triangle[0],triangle[1],triangle[2],normal))
        fp.close()

    #load binary stl file check wikipedia for the binary layout of the file
    #we use the struct library to read in and convert binary data into a format we can use
    def load_binary_stl(self,filename):
        fp=open(filename,'rb')
        h=fp.read(80)

        l=struct.unpack('I',fp.read(4))[0]
        count=0
        while True:
            try:
                p=fp.read(12)
                if len(p)==12:
                    n=struct.unpack('f',p[0:4])[0],struct.unpack('f',p[4:8])[0],struct.unpack('f',p[8:12])[0]
                  
                p=fp.read(12)
                if len(p)==12:
                    p1=struct.unpack('f',p[0:4])[0],struct.unpack('f',p[4:8])[0],struct.unpack('f',p[8:12])[0]

                p=fp.read(12)
                if len(p)==12:
                    p2=struct.unpack('f',p[0:4])[0],struct.unpack('f',p[4:8])[0],struct.unpack('f',p[8:12])[0]

                p=fp.read(12)
                if len(p)==12:
                    p3=struct.unpack('f',p[0:4])[0],struct.unpack('f',p[4:8])[0],struct.unpack('f',p[8:12])[0]

                new_tri=(n,p1,p2,p3)

                if len(new_tri)==4:
                    tri=createtriangle(p1,p2,p3,n)
                    self.model.append(tri)
                count+=1
                fp.read(2)

                if len(p)==0:
                    break
            except EOFError:
                break
        fp.close()