Need Help Parsing A File - Moved form mel

[duckspeaker]

I'm bringing instanced object over from an XML script in another application.
In the file there are many objects, each with a variety of instances identified.

I need to parse the file and pull out all the instances (with translation, rotation, and scale information) for each object.
But I'm having trouble.

Example of what I'm looking at:

[Object 1]
_____[Instance]
__________Translation:
__________Rotation:
__________Scale:
_____[Instance]
__________Translation:
__________Rotation:
__________Scale:
_____[Instance]
__________Translation:
__________Rotation:
__________Scale:
[Object 2]
_____[Instance]
__________Translation:
__________Rotation:
__________Scale:
_____[Instance]
__________Translation:
__________Rotation:
__________Scale:

I think I'm looking at some sort of embedded FOR statment...but I'm unsure.
Any thoughts?

[akjones]

parsing xml would be much easier in Python. If you're new to this, start here: http://oreilly.com/catalog/pythonxml/chapter/ch01.html

[joojaa]

Yes but theres hardly any parsing to do in file like this. Ofcourse having a more roboust parser heps if you need to re purpose the script.

IN any cese doing something like this in script is not really fruitful. Look at the api for file trasnlation, that way it becomes just a import operation amongst others.

PS: Note you can probably easily xml transfom it into collada. I mean its allready xml and maya knows how to read it.

[duckspeaker]

QUOTE(Joojaa @ 06/08/09, 08:43 AM) [snapback]309109[/snapback]
....IN any cese doing something like this in script is not really fruitful. Look at the api for file trasnlation, that way it becomes just a import operation amongst others.

The file I'm trying to read doesn't contain all the information for the object.
So I've got the MEL Script creating a reference object in the Maya file and generating Instances based on the only info given (Trans, Rotate, Scale).

(As is...I'm going to have to convert the Rotation to be more "maya like")

I'm sure there must be a way to do this...
(MEL is certainly a stretch, but I'm betting the API is way out of my league right now)

[joojaa]

QUOTE(Duckspeaker @ 06/08/09, 06:07 PM) [snapback]309112[/snapback]
The file I'm trying to read doesn't contain all the information for the object.

Yes but it must contain info on what the t object would eventually be or its of not much use. Importers dont nee dto import geometry. IN fact many fo them dont, such as the move.

QUOTE
I'm sure there must be a way to do this...

Yes.

Except you asked how to PARSE XML. And got aswers on how to parse (use python), parsing does not maean the intent of making it mayalike object.

QUOTE
(As is...I'm going to have to convert the Rotation to be more "maya like")

So your question is not about parsing then? It a question about transform? Well ok what kind fo trasform stack does the target device have.

In any case the reason this si not fruitfull is that mayas not exactly a database, and its all fine if you nee dto do this once, but if you have a series of theese files that describe a animation then its nolonger comfortable to do in SCRIPT. then you need a node.

[joojaa]

Incidentally Im trying to fill the gaps for Do The Simplest Thing That Could Possibly Work, which isn't the first thing that pops in my mind.

[duckspeaker]

QUOTE(Joojaa @ 06/08/09, 09:26 AM) [snapback]309118[/snapback]
Yes but it must contain info on what the t object would eventually be or its of not much use.

I can derive the filenames--I will bring it in as a reference object and Instance all iterations.
QUOTE(Joojaa @ 06/08/09, 09:26 AM) [snapback]309118[/snapback]
Except you asked how to PARSE XML. And got aswers on how to parse (use python)...

I tried a bit longer with MEL...so close...but not quite.

I'm looking into Python now...it's kicking my butt.
But I do see the potential, and the power of Python.
QUOTE(Joojaa @ 06/08/09, 09:26 AM) [snapback]309118[/snapback]
So your question is not about parsing then? It a question about transform? Well ok what kind fo trasform stack does the target device have.

Not really...the rotation in the XML is stored differently so I was anticipating having to write something to convert it to Maya friendly...I shouldn't have brought it up, as it distracts from the goal of first getting the information out.

So I'm on to Python..
I feel a bit like a young child cast out into the forest.

[joojaa]

QUOTE
I'm looking into Python now...it's kicking my butt.

Stop stop stop. You can never get code done if you just go about it just as long as i get this step done you will potentially fall into some sort of will never become usefull spagetti, limbo. You must understand what it is your deeming the computer to do on BOTH ends before you can attempt to do a code.

QUOTE(Duckspeaker @ 06/09/09, 06:15 PM) [snapback]309191[/snapback]
Not really...the rotation in the XML is stored differently so I was anticipating having to write something to convert it to Maya friendly...I shouldn't have brought it up, as it distracts from the goal of first getting the information out.

You mean like axis angles or?

So answer yourself following questions:

Does it need to be ready on monday*

Do you need to change that code. Odds are you will when you do one bad step in the beginning can cause you headaches beyond untold nightmares in the future. A ten minute botch up 6 mnths from now can mean 6 MONTHS of work

Do you need to import or extend the data for animation? Do you really ever need to? See if you do all youve done so far may be down the drain.

Do you understand how maya works? Do you really... i mean many users who have used maya for 3 years dont have a clue. That is why they have hard time doing scripting in maya.

Is the file format forever fixed, if it is you can just write the parser yourself. IF NOT use a generic xml parser and only concentrate on understanding the tree structural leaves. Then if more vocabulary appears elsewhere you can just understand magically what you already have understanding of.

does the data need to be refreshhed form file

Code is like investment into a share, know it before you invest in it.

Do you understand what the difference between a database and a node network. See you can treat maya as a database, IF you are very careful not to try to overstep your bounds. In genaral maya hates it, so it helps to know up front.

If you answer yes to 2,3,5 then design a bit up front, we can help.

if you answer yes to 3 or 6 write a node. It may seem surprising but its not actually much more code for your part, its just a lot scarier but the chasm is as wide its just 12 stories higher than the other.

this is a special case. Where you go and say to your boss, can i have that in writing please. Because WHEN the s thits the fan you can just tell your boss i told you so. Else its better to work 2 hours a day for 4 weeks rather than 8 hours brute forcing. Just as long as you dont overdo it. In this case i would buy the code form somebody, trust me its cheaper on long run.

Pasring a file into python

should look something like this didnt test wrote out of my head.

CODE
from xml.dom.ext.reader import Sax2
from xml.dom import EMPTY_NAMESPACE

reader = Sax2.Reader()
doc = reader.fromStream(open('filename.xml'))
objects= doc.getElementsByTagName('Object')
#mayacode for locating object
for obj in objects:
  instances= obj.getElementsByTagName('Instance')
  #mayacode for making a new isntace
  for inst in instances:
    trans=inst.getElementsByTagName('Translation')
    dataInTransform=trans[0].data
    #transform instance
    trans=inst.getElementsByTagName('Rotation')
    ...

PS i moved the entire thread to python, leaving link in the mel forum thisway the path stays intact

[joojaa]

Damn the default set doent incluse the ext tree. That make sit a bit trickyer... use minidom

example assuming the c:\temp\test.xml looks like:

CODE

  
    
         0 0 0
         0.0 90.0 15.0
         1.0 1.0 1.0
    
    
         10.0 10.0 10.0
         0.0 0.0 0.0
         1.0 2.0 1.0
    
  

Then:
CODE
from xml.dom.minidom import parse
import maya.cmds as cmds
from xml.dom import EMPTY_NAMESPACE

def getValues(type):
  """getValues(type)
  Return the tag of types content as list of floats"""
  data=inst.getElementsByTagName(type)
  length=len(data)
  if length!=1:
    raise Exception('inconsitent data wrong number of ('+
                     str(length)+') children of type '+type)
  dataInTransform=data[0]
  return [float(x) for x in dataInTransform.firstChild.data.split(" ")]

doc  = parse('c:\temp\test.xml')
objects= doc.getElementsByTagName('object')
#mayacode for locating object
#to demo I make a sphere
sphere=cmds.sphere( r=1 )
for obj in objects:
  instances= obj.getElementsByTagName('instance')
  for inst in instances:
    #mayacode for making a new instance
    instObj=cmds.instance(sphere[0])

    tx,ty,tz=getValues('translation')
    cmds.move(tx,ty,tz,instObj)
    rx,ry,rz=getValues('rotation')
    cmds.rotate(rx,ry,rz,instObj)
    sx,sy,sz=getValues('scale')
    cmds.scale(sx,sy,sz,instObj)

cmds.delete(sphere[0])

PS: i do not advocate that this is a good approach or that it works because the approach has many caveats thet depend on WHAT EXACTLY IT IS YOUR AFTER.

PPS: If you find this overty tedious get Amara

[duckspeaker]

QUOTE(Joojaa @ 06/09/09, 10:35 AM) [snapback]309194[/snapback]
So answer yourself following questions:

Does it need to be ready on monday*

Do you need to change that code. Odds are you will when you do one bad step in the beginning can cause you headaches beyond untold nightmares in the future. A ten minute botch up 6 mnths from now can mean 6 MONTHS of work

Do you need to import or extend the data for animation? Do you really ever need to? See if you do all youve done so far may be down the drain.

Do you understand how maya works? Do you really... i mean many users who have used maya for 3 years dont have a clue. That is why they have hard time doing scripting in maya.

Is the file format forever fixed, if it is you can just write the parser yourself. IF NOT use a generic xml parser and only concentrate on understanding the tree structural leaves. Then if more vocabulary appears elsewhere you can just understand magically what you already have understanding of.

does the data need to be refreshhed form file

Code is like investment into a share, know it before you invest in it.

Do you understand what the difference between a database and a node network. See you can treat maya as a database, IF you are very careful not to try to overstep your bounds. In genaral maya hates it, so it helps to know up front.

• Doesnt' need to be done Monday
• ??
• This isn't for animation...just moving objects from proprietary engine to Maya for special case rendering.
• I probably don't understand how maya "really" works---trying to learn
• The file format I am trying to read is fixed and consistent
• The data does not need to be refreshed--it's fixed
• This is an opportunity to learn...if I understand you right...to know
• I've used databases...but I'm not sure about node networks, or how that applies to parsing a file (my objective right now)

You clearly have a good grasp of Maya and Python.
I appreciate the help.

Thanks

[joojaa]

QUOTE(Duckspeaker @ 06/10/09, 06:18 PM) [snapback]309239[/snapback]
This is an opportunity to learn...if I understand you right...to know

Well not quite, by the time you encounter stuff like it would be nice, need or something of this kind its too late. Its too late because your running and your running in dark room full of nasty sharp pointing devices. Sooner or later you'll run into one. So try to walk carefully instead of storming about.

Its only a investment if you can design it up front you know. Otherwise its just a development debt

QUOTE
but I'm not sure about node networks, or how that applies to parsing a file

When you create something into maya, its a node network entry in a database of networks. Now yoru not really supposed to populate the maya base but use networks to do the solving for you.

So for example if you needed 10,000 flowers you WOULD NOT do a loop to copy or even instance the flower 10,000 times. You could do 1 flower and a particle system and use particleInstancer. OR better yet just directly export the data into a mi file and let the renderer include it at render time. Bypassing maya altogether.

[duckspeaker]

QUOTE(Joojaa @ 06/09/09, 01:00 PM) [snapback]309199[/snapback]
Damn the default set doent incluse the ext tree. That make sit a bit trickyer... use minidom

example assuming the c:\temp\test.xml looks like:

...cut...

PS: i do not advocate that this is a good approach or that it works because the approach has many caveats thet depend on WHAT EXACTLY IT IS YOUR AFTER.

PPS: If you find this overty tedious get Amara

Wow...you have been very generous with your time. Thank You!

The file I'm trying to read from looks more like this:
(I should have posted initially, but I didn't think I'd find this so difficult)

  CODE

            
                
                    
                        
                        
                        
                    
                
                
                    
                        
                        
                        
                    
                
        
        
                ....and so on

The files contain an unknown number of objects with a varying number of instances for each.

I'm looking into minidom to see how I might get what I need out of the xml file...but most of the information I'm coming across isn't very newbie friendly---much of it doesn't provide code examples.

(Originally (MEL) I was planning on breaking up each line and pulling out predictable pieces using tokenize. This was working except that I couldn't get variables to work outside of nested "for" and "if" statements)