bvh.py

import string

# Node
class Node:
    def __init__(self, root=False):
        self.name = None
        self.channels = []
        self.offset = (0,0,0)
        self.children = []
        self._is_root = root
        self.order = ""

    def isRoot(self):
        return self._is_root

    def isEndSite(self):
        return len(self.children)==0
    

# BVHReader
class BVHReader:
    """Read BioVision Hierarchical (BVH) files.
"""

    def __init__(self, filename):

        self.filename = filename
        # A list of unprocessed tokens (strings)
        self.tokenlist = []
        # The current line number
        self.linenr = 0

        # Root node
        self._root = None
        self._nodestack = []

        # Total number of channels
        self._numchannels = 0

    def onHierarchy(self, root):
        pass

    def onMotion(self, frames, dt):
        pass

    def onFrame(self, values):
        pass

    # read
    def read(self):
        """Read the entire file.
"""
        self.fhandle = file(self.filename)

        self.readHierarchy()
        self.onHierarchy(self._root)
        self.readMotion()

    # readMotion
    def readMotion(self):
        """Read the motion samples.
"""
        # No more tokens (i.e. end of file)? Then just return
        try:
            tok = self.token()
        except StopIteration:
            return
        
        if tok!="MOTION":
            raise SyntaxError, "Syntax error in line %d: 'MOTION' expected, got '%s' instead"%(self.linenr, tok)

        # Read the number of frames
        tok = self.token()
        if tok!="Frames:":
            raise SyntaxError, "Syntax error in line %d: 'Frames:' expected, got '%s' instead"%(self.linenr, tok)

        frames = self.intToken()

        # Read the frame time
        tok = self.token()
        if tok!="Frame":
            raise SyntaxError, "Syntax error in line %d: 'Frame Time:' expected, got '%s' instead"%(self.linenr, tok)
        tok = self.token()
        if tok!="Time:":
            raise SyntaxError, "Syntax error in line %d: 'Frame Time:' expected, got 'Frame %s' instead"%(self.linenr, tok)

        dt = self.floatToken()

        self.onMotion(frames, dt)

        # Read the channel values
        for i in range(frames):
            s = self.readLine()
            a = s.split()
            if len(a)!=self._numchannels:
                raise SyntaxError, "Syntax error in line %d: %d float values expected, got %d instead"%(self.linenr, self._numchannels, len(a))
            values = map(lambda x: float(x), a)
            self.onFrame(values)


    # readHierarchy
    def readHierarchy(self):
        """Read the skeleton hierarchy.
"""
        tok = self.token()
        if tok!="HIERARCHY":
            raise SyntaxError, "Syntax error in line %d: 'HIERARCHY' expected, got '%s' instead"%(self.linenr, tok)

        tok = self.token()
        if tok!="ROOT":
            raise SyntaxError, "Syntax error in line %d: 'ROOT' expected, got '%s' instead"%(self.linenr, tok)

        self._root = Node(root=True)
        self._nodestack.append(self._root)
        self.readNode()

    # readNode
    def readNode(self):
        """Read the data for a node.
"""

        # Read the node name (or the word 'Site' if it was a 'End Site'
        # node)
        name = self.token()
        self._nodestack[-1].name = name
        
        tok = self.token()
        if tok!="{":
            raise SyntaxError, "Syntax error in line %d: '{' expected, got '%s' instead"%(self.linenr, tok)

        while 1:
            tok = self.token()
            if tok=="OFFSET":
                x = self.floatToken()
                y = self.floatToken()
                z = self.floatToken()
                self._nodestack[-1].offset = (x,y,z)
            elif tok=="CHANNELS":
                n = self.intToken()
                channels = []
                for i in range(n):
                    tok = self.token()
                    if tok not in ["Xposition", "Yposition", "Zposition",
                                  "Xrotation", "Yrotation", "Zrotation"]:
                        raise SyntaxError, "Syntax error in line %d: Invalid channel name: '%s'"%(self.linenr, tok)
                    channels.append(tok)
                self._numchannels += len(channels)
                self._nodestack[-1].channels = channels
            elif tok=="JOINT":
                node = Node()
                self._nodestack[-1].children.append(node)
                self._nodestack.append(node)
                self.readNode()
            elif tok=="End":
                node = Node()
                self._nodestack[-1].children.append(node)
                self._nodestack.append(node)
                self.readNode()
            elif tok=="}":
                if self._nodestack[-1].isEndSite():
                    self._nodestack[-1].name = "End Site"
                self._nodestack.pop()
                break
            else:
                raise SyntaxError, "Syntax error in line %d: Unknown keyword '%s'"%(self.linenr, tok)
        

    # intToken
    def intToken(self):
        """Return the next token which must be an int.
"""

        tok = self.token()
        try:
            return int(tok)
        except ValueError:
            raise SyntaxError, "Syntax error in line %d: Integer expected, got '%s' instead"%(self.linenr, tok)

    # floatToken
    def floatToken(self):
        """Return the next token which must be a float.
"""

        tok = self.token()
        try:
            return float(tok)
        except ValueError:
            raise SyntaxError, "Syntax error in line %d: Float expected, got '%s' instead"%(self.linenr, tok)

    # token
    def token(self):
        """Return the next token."""

        # Are there still some tokens left? then just return the next one
        if self.tokenlist!=[]:
            tok = self.tokenlist[0]
            self.tokenlist = self.tokenlist[1:]
            return tok

        # Read a new line
        s = self.readLine()
        self.createTokens(s)
        return self.token()

    # readLine
    def readLine(self):
        """Return the next line.

Empty lines are skipped. If the end of the file has been
reached, a StopIteration exception is thrown. The return
value is the next line containing data (this will never be an
empty string).
"""
        # Discard any remaining tokens
        self.tokenlist = []
      
        # Read the next line
        while 1:
            s = self.fhandle.readline()
            self.linenr += 1
            if s=="":
                raise StopIteration
            return s

    # createTokens
    def createTokens(self, s):
        """Populate the token list from the content of s.
"""
        s = s.strip()
        a = s.split()
        self.tokenlist = a