#######################################
# stl.py - for Blender STL exporting  #
# By Chris Want using code pinched    #
# from Jan Walter's POV export script #
#######################################

import Blender
from math import sqrt
from struct import pack

# *** note ***
# Must specify an object name for blender 2.10 or later.
# For blender 2.04 or earlier the select mesh gets exported
meshObjectName = "Plane"

# STL has two subformats: a binary one that is
# used if exportFormat = "Binary" or a text format
# that is used otherwise
exportFormat = "Text"

class StlExport:
	def __init__(self,name,format):
		self.file     = None
		self.numFaces = 0

		if self.NMeshQuery():
			self.object    = Blender.Object.GetSelected()[0]
			self.name      = self.object.data.name
			self.writeData = self.writeDataOldApi
		else:
			self.object    = Blender.getObject(name)
			self.name      = name
			self.writeData = self.writeDataNewApi

		if format == "Binary":
			self.writeHead = self.writeHeadBinary
			self.writeFace = self.writeFaceBinary
			self.writeTail = self.writeTailBinary
			self.writemode = "wb"
		else:
			self.writeHead = self.writeHeadText
			self.writeFace = self.writeFaceText
			self.writeTail = self.writeTailText
			self.writemode = "w"

	def export(self):
		if self.object=="None":
			print "Select a mesh object and try again"
		else:
			self.writeData()

	def writeDataOldApi(self):
		filename = self.name + ".stl"
		mesh  = Blender.NMesh.GetRaw(self.name)

		print "exporting to file " + filename + " ..."
		self.file = open(filename, self.writemode)

		self.writeHead(self.name)
		for face in mesh.faces:
			self.writeFace(face.v[0].co,face.v[1].co,face.v[2].co)
			try:
				self.writeFace(face.v[0].co,face.v[2].co,face.v[3].co)
			except:
				pass
		self.writeTail()
		self.file.close()
		print "All done -- have a nice day!"

	def writeDataNewApi(self):
		filename = self.name + ".stl"
		if Blender.isMesh(self.name):
			print "exporting to file " + filename + " ..."
			self.file = open(filename, self.writemode)

			mesh    = Blender.getMesh(self.object.data)

			self.writeHead(self.name)
			for face in mesh.faces:
				self.writeFace(mesh.vertices[face[0]],mesh.vertices[face[1]],mesh.vertices[face[2]])
				if mesh.vertices[face[3]]:
					self.writeFace(mesh.vertices[face[0]],mesh.vertices[face[2]],mesh.vertices[face[3]])
			self.writeTail()
			self.file.close()
			print "All done -- have a nice day!"
		else:
			print "Sorry can export meshes only ..."


	def writeHeadText(self,meshname):
		self.file.write("solid " + meshname + "\n")

	def writeHeadBinary(self,meshname):
		self.file.write("%-80.80s    " % meshname)

	def writeFaceText(self,vert1,vert2,vert3):
		fNormal = self.getFaceNormal(vert1,vert2,vert3)
		self.file.write("  facet normal %f %f %f\n" % (fNormal[0],fNormal[1],fNormal[2]))
		self.file.write("    outer loop\n")
		self.file.write("      vertex %f %f %f\n" % (vert1[0],vert1[1],vert1[2]))
		self.file.write("      vertex %f %f %f\n" % (vert2[0],vert2[1],vert2[2]))
		self.file.write("      vertex %f %f %f\n" % (vert3[0],vert3[1],vert3[2]))
		self.file.write("    endloop\n")
		self.file.write("  endfacet\n")

	def writeFaceBinary(self,vert1,vert2,vert3):
		fNormal = self.getFaceNormal(vert1,vert2,vert3)
		self.file.write(pack("fff",fNormal[0],fNormal[1],fNormal[2]))
		self.file.write(pack("fff",vert1[0],vert1[1],vert1[2]))
		self.file.write(pack("fff",vert2[0],vert2[1],vert2[2]))
		self.file.write(pack("fff",vert3[0],vert3[1],vert3[2]))
		self.file.write("  ")
		self.numFaces=self.numFaces+1

	def writeTailText(self):
		self.file.write("endsolid\n")

	def writeTailBinary(self):
		self.file.seek(80)
		self.file.write("%4.4s" % pack("L",self.numFaces))

	def getFaceNormal(self,v1,v2,v3):
		a = [v2[0]-v1[0],v2[1]-v1[1],v2[2]-v1[2]]
		b = [v3[0]-v1[0],v3[1]-v1[1],v3[2]-v1[2]]
		n = [a[1]*b[2] - a[2]*b[1],a[2]*b[0]-a[0]*b[2],a[0]*b[1]-a[1]*b[0]]
		nlen = sqrt(n[0]**2+n[1]**2+n[2]**2)
		return [n[0]/nlen,n[1]/nlen,n[2]/nlen]

	def NMeshQuery(self): 
		try: 
			dir(Blender.NMesh) 
		except: 
			return 0 
		else: 
			return 1


stlexport = StlExport(meshObjectName,exportFormat)
stlexport.export()