Manipulating Objects, Part 3

On 2 Aug, 2015 By Austin With 0 Comments

We’ve covered getting geometry data from an existing object and building a new object from raw data. Now we’ll start looking at non-geometry related elements of a polygon object. Continue using the cube example from the previous parts in this series lets see how to get its UV information.

Start by creating a cube called Box.

import maya.cmds as cmds
    
# Create the box.
cmds.polyCube( name='box' )

import maya.cmds as cmds

# Create the box.

cmds.polyCube( name='box' )

Now get Box’s shape MObject as shown in Part 1. This will be used to confirm that we’re dealing with a poly mesh object.

import maya.OpenMaya as OpenMaya

# Utility junk.
def getMDagPath( name ):
    '''
    Get the MDagPath of the object.
    
    @param name: String. Name of object.
    @return: MDagPath.
    '''
    sel_list = OpenMaya.MSelectionList()
    sel_list.add( name )
    dag = OpenMaya.MDagPath()
    component = OpenMaya.MObject()
    sel_list.getDagPath( 0, dag, component )
    return dag
    
# Create the box.
cmds.polyCube( name='box' )

# Get the polyMesh of Box.
box_dag = getMDagPath( 'box' )

# Get Box's mesh.
box_dag.extendToShapeDirectlyBelow( 0 )
shape_obj = box_dag.node()

import maya.OpenMaya as OpenMaya

# Utility junk.

def getMDagPath( name ):

'''

Get the MDagPath of the object.

@param name: String. Name of object.

@return: MDagPath.

'''

sel_list = OpenMaya.MSelectionList()

sel_list.add( name )

dag = OpenMaya.MDagPath()

component = OpenMaya.MObject()

sel_list.getDagPath( 0, dag, component )

return dag

# Create the box.

cmds.polyCube( name='box' )

# Get the polyMesh of Box.

box_dag = getMDagPath( 'box' )

# Get Box's mesh.

box_dag.extendToShapeDirectlyBelow( 0 )

shape_obj = box_dag.node()

The function set MFnMesh is used to retrieve the UV data from the mesh.

# Test to see what kind of shape we are dealing with.
if shape_obj.apiType() == OpenMaya.MFn.kMesh:
    mfn_mesh = OpenMaya.MFnMesh( box_dag )

# Test to see what kind of shape we are dealing with.

if shape_obj.apiType() == OpenMaya.MFn.kMesh:

mfn_mesh = OpenMaya.MFnMesh( box_dag )

We’ll be using a few member functions from MFnMesh to get the UV information.

numUVSets(), use this to get the number of UV sets applied to the object.
numUVs(), use this to get the number of UVs the object contains.
getUVs(), use this to get each UVs U and V values.

The first two are straight forward and don’t warrant a more detailed explanation. However, getUVs() does requires two parameters be passed into the function. These are both MFloatArrays with no elements which getUVs() fills with the U and V data. Elements of a MFloatArray can be accessed the same as a Python list.

    # Number of UV sets.
    print 'Number of UV Sets: {0}'.format(mfn_mesh.numUVSets())
 
    # Number of UVs.
    print 'Number of UVs: {0}'.format(mfn_mesh.numUVs())
    
    # Get the UVs.
    UArray = OpenMaya.MFloatArray()
    VArray = OpenMaya.MFloatArray()
    
    mfn_mesh.getUVs( UArray, VArray )
    
    for n in xrange(len(UArray)):
        print 'UV {0}: {1}, {2}'.format(n+1, UArray[n], VArray[n])

# Number of UV sets.

print 'Number of UV Sets: {0}'.format(mfn_mesh.numUVSets())

# Number of UVs.

print 'Number of UVs: {0}'.format(mfn_mesh.numUVs())

# Get the UVs.

UArray = OpenMaya.MFloatArray()

VArray = OpenMaya.MFloatArray()

mfn_mesh.getUVs( UArray, VArray )

for n in xrange(len(UArray)):

print 'UV {0}: {1}, {2}'.format(n+1, UArray[n], VArray[n])

Running this code on our box produces the following print out. I’ve also included a couple images showing the locations of each UV.

UV locations on the box.

UV locations on the unwrapped geometry.

Number of UV Sets: 1
Number of UVs: 14
UV 1: 0.330000013113, 0.0
UV 2: 0.66333335638, 0.0
UV 3: 0.330000013113, 0.25
UV 4: 0.66333335638, 0.25
UV 5: 0.330000013113, 0.5
UV 6: 0.66333335638, 0.5
UV 7: 0.330000013113, 0.75
UV 8: 0.66333335638, 0.75
UV 9: 0.330000013113, 1.0
UV 10: 0.66333335638, 1.0
UV 11: 1.0, 0.0
UV 12: 1.0, 0.25
UV 13: 0.0, 0.0
UV 14: 0.0, 0.25

Number of UV Sets: 1

Number of UVs: 14

UV 1: 0.330000013113, 0.0

UV 2: 0.66333335638, 0.0

UV 3: 0.330000013113, 0.25

UV 4: 0.66333335638, 0.25

UV 5: 0.330000013113, 0.5

UV 6: 0.66333335638, 0.5

UV 7: 0.330000013113, 0.75

UV 8: 0.66333335638, 0.75

UV 9: 0.330000013113, 1.0

UV 10: 0.66333335638, 1.0

UV 11: 1.0, 0.0

UV 12: 1.0, 0.25

UV 13: 0.0, 0.0

UV 14: 0.0, 0.25

Here is the complete code for this post.

import maya.cmds as cmds
import maya.OpenMaya as OpenMaya

# Utility junk.
def getMDagPath( name ):
    '''
    Get the MDagPath of the object.
    
    @param name: String. Name of object.
    @return: MDagPath.
    '''
    sel_list = OpenMaya.MSelectionList()
    sel_list.add( name )
    dag = OpenMaya.MDagPath()
    component = OpenMaya.MObject()
    sel_list.getDagPath( 0, dag, component )
    return dag
    
# Create the box.
cmds.polyCube( name='box' )

# Get the polyMesh of Box.
box_dag = getMDagPath( 'box' )

# Get Box's mesh.
box_dag.extendToShapeDirectlyBelow( 0 )
shape_obj = box_dag.node()

# Test to see what kind of shape we are dealing with.
if shape_obj.apiType() == OpenMaya.MFn.kMesh:
    mfn_mesh = OpenMaya.MFnMesh( box_dag )

    # Number of UV sets.
    print 'Number of UV Sets: {0}'.format(mfn_mesh.numUVSets())
 
    # Number of UVs.
    print 'Number of UVs: {0}'.format(mfn_mesh.numUVs())
    
    # Get the UVs.
    UArray = OpenMaya.MFloatArray()
    VArray = OpenMaya.MFloatArray()
    
    mfn_mesh.getUVs( UArray, VArray )
    
    for n in xrange(len(UArray)):
        print 'UV {0}: {1}, {2}'.format(n+1, UArray[n], VArray[n])

import maya.cmds as cmds

import maya.OpenMaya as OpenMaya

# Utility junk.

def getMDagPath( name ):

'''

Get the MDagPath of the object.

@param name: String. Name of object.

@return: MDagPath.

'''

sel_list = OpenMaya.MSelectionList()

sel_list.add( name )

dag = OpenMaya.MDagPath()

component = OpenMaya.MObject()

sel_list.getDagPath( 0, dag, component )

return dag

# Create the box.

cmds.polyCube( name='box' )

# Get the polyMesh of Box.

box_dag = getMDagPath( 'box' )

# Get Box's mesh.

box_dag.extendToShapeDirectlyBelow( 0 )

shape_obj = box_dag.node()

# Test to see what kind of shape we are dealing with.

if shape_obj.apiType() == OpenMaya.MFn.kMesh:

mfn_mesh = OpenMaya.MFnMesh( box_dag )

# Number of UV sets.

print 'Number of UV Sets: {0}'.format(mfn_mesh.numUVSets())

# Number of UVs.

print 'Number of UVs: {0}'.format(mfn_mesh.numUVs())

# Get the UVs.

UArray = OpenMaya.MFloatArray()

VArray = OpenMaya.MFloatArray()

mfn_mesh.getUVs( UArray, VArray )

for n in xrange(len(UArray)):

print 'UV {0}: {1}, {2}'.format(n+1, UArray[n], VArray[n])

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