# Difference between revisions of "Rebuild Curve"

This example shows how to create a command which can read curve attributes. It is made up of the command itself, as well as a visitor object which we use to scan a mesh layer for curve polygons.

```import lx
import lxu.select
import lxu.command
import lxifc
from math import floor

def dSqr(vec1, vec2):
'''Quick function to get the distance squared between two points'''
dist = 0.0
for i in range(3):
dist += (vec2[i] - vec1[i])**2
return dist

class CurveFinder(lxifc.Visitor):
'''This visitor object will scan through selected polygons and
create a dictionary of those polygons who are curves.  The ID of the
polygon will be the key, and the value will be the position or its root
vertex.  Later, we'll compare this position to the position of curve
objects we get to make sure we're only affecting the curves the user intends.'''
def __init__(self, polyAccessor, pointAccessor):
self.poly = polyAccessor
self.point = pointAccessor
self.curves = {}

def vis_Evaluate(self):
if self.poly.Type() == lx.symbol.iPTYP_CURVE:
p = self.poly.VertexByIndex(0)
self.point.Select(p)
pos = self.point.Pos()
ID = self.poly.ID()
self.curves[ID] = pos

class CurvePoints(lxu.command.BasicCommand):
def __init__(self):
'''After initializing the command, arguments are added one by one.  These
arguments can then be referenced later by the order they were added, so
the first argument will be index 0, the second index 1, etc.'''
lxu.command.BasicCommand.__init__(self)

self.basic_SetFlags(2, lx.symbol.fCMDARG_OPTIONAL)
self.basic_SetFlags(3, lx.symbol.fCMDARG_OPTIONAL)
'''Adding a argument requires an internal string name for the argument, and
a type for the argument.  By default all arguments are required, but we can
use the basic_SetFlags method to change that if we need to'''

def fire(self, CMD):
'''Call commands without lx.eval'''
lx.service.Command().ExecuteArgString(-1, lx.symbol.iCTAG_NULL, CMD)

'''This sets the user name for the argument of a given index.  Ideally, these
user names should exist in a message table inside of a config, but for this
example it's not really all that important'''

argNames = ['Use Spacing Distance', 'Remove Original Curve',
'Point Count', 'Point Spacing']
return argNames[index]

'''This sets the user name for the command itself.  Again, we should
ideally use a message table, but we will just use a string for simplicity'''
return 'Rebuild Curve'

'''If the user doesn't provide all required arguments, modo opens a dialog
to ask for them.  When this happens, the cmd_DialogInit is called which
allows us to set default values for our the command arguments'''
self.attr_SetInt(0, 0)
self.attr_SetInt(1, 1)
self.attr_SetInt(2, 10)
self.attr_SetFlt(3, .05)

def cmd_ArgEnable(self,arg):
'''When the command dialog opens and when the user interacts with it,
modo calls this method for each of our arguments.  That gives us a chance
to read what the current values for arguments are, and choose if we need
to disable an argument'''
if self.attr_GetInt(0) and arg == 2:
lx.throw(lx.symbol.e_CMD_DISABLED)
elif not self.attr_GetInt(0) and arg == 3:
lx.throw(lx.symbol.e_CMD_DISABLED)
return lx.symbol.e_OK

def cmd_Flags(self):
'''cmd_Flags tells modo what kind of command we have.  Since we're changing
the state of the scene by altering geometry, we need to make this an undoable
command'''
return lx.symbol.fCMD_MODEL | lx.symbol.fCMD_UNDO

def getCurve(self, layerScan):
'''For organization, the command is split into two parts.  This method grabs
a curve object from the current mesh layer and returns it to the main execution
method.  If a curve is selected, we find which curve in the curve Group is the
same as the selected one, and return it.  Otherwise, we return all curves
we find.'''

# Layerscan lets us get the mesh as an item object, and as an editable mesh.
curveItem = layerScan.MeshItem(0)
self.mesh = layerScan.MeshEdit(0)
self.poly = self.mesh.PolygonAccessor()
self.points = self.mesh.PointAccessor()

'''Getting a curve Group object from an item requires reading the
crvGroup channel, casting the channel's value object as a value
reference, and finally casting the object from the value reference as
a curve group.  The curve group is an item which contains all the curves
within the provided item.  We access an individual curve by using the
ByIndex() method'''
crvChan = curveItem.ChannelLookup('crvGroup')
valRef = lx.object.ValueReference(crvValObj)
curveGroup = lx.object.CurveGroup(valRef.GetObject())
if curveGroup.Count()<1:
return None

'''We use our visitor to scan through any selected polygons and check if
they are curves.  If so, we make a dictionary with those curve IDs and
the root vertex position.'''
curveVis = CurveFinder(self.poly, self.points)
selM = lx.service.Mesh().ModeCompose('select', None)
self.poly.Enumerate(selM, curveVis, 0)

'''For every curve that the visitor found, we want to pair it with a
curve object from the curve group.  We'll make a new dictionary, where
the curve's ID is the key again, but the value will be the curve object
itself.'''
retCurves = {}
for selCurve in curveVis.curves:
dist = 9**99
'''There are no direct links to find which curve in the curve group
belongs to a specific polygon in a mesh, so we need to compare the root
position of the curve with the root vertices position.  We assume the
curve object with a root position closest to a given root vertex is the
same curve.'''
for i in range(curveGroup.Count()):
curve = curveGroup.ByIndex(i)
pos = curve.Position()
tmpD = dSqr(curveVis.curves[selCurve], pos)
if tmpD < dist:
dist = tmpD
idx = i
retCurves[selCurve] = curveGroup.ByIndex(idx)

return retCurves

def basic_Execute(self, msg, flags):
'''Even though the point count and spacing distance arguments are both
optional, one of them has to be set.  We check that first.'''
if self.dyna_IsSet(2) or self.dyna_IsSet(3):
mode = self.attr_GetInt(0)
'''Next we need to make sure we didn't get a spacing distance of 0
or less, or a point count of less than 2'''
if mode:
dist = self.attr_GetFlt(3)
if dist <= 0:
return lx.symbol.e_ABORT
else:
ptCount = self.attr_GetInt(2)
if ptCount <2:
return lx.symbol.e_ABORT

'''Finally, we can get a layerscan object in order to check if there
are curves in the mesh.'''
self.scene = lxu.select.SceneSelection().current()
ls = lx.service.Layer()
lscan = ls.ScanAllocate(lx.symbol.f_LAYERSCAN_EDIT | lx.symbol.f_LAYERSCAN_MARKPOLYS)
curves = self.getCurve(lscan)
if not curves:
self.e_NOCURVE()
lscan.Apply()
return lx.symbol.e_ABORT

'''All our tests passed, and we have at least 1 curve object to rebuild'''
killSwitch = self.attr_GetInt(1)
for ID in curves:
curve = curves[ID]
'''First we get a list of all the positions we want to form
our curve from.  Then we generate points there using a Point object'''
if mode:
ptCount = int(floor(curve.Length()/dist))
pts = []
for i in range(ptCount):
curve.SetLenFraction(float(i)/(ptCount-1))
pts.append(curve.Position())
ptList = []
for i in pts:
ptList.append(self.points.New(i))
'''We need to add the IDs from each newly created point into a
storage object, and using that storage object we can create a polygon'''
pBuf = lx.object.storage('p')
pBuf.setSize(len(ptList))
pBuf.set(ptList)
polyID = self.poly.New(lx.symbol.iPTYP_CURVE, pBuf, len(ptList), 0)
'''Finally we check if the user wants to remove the original curve.
If they do, we need to remove each of the verts, and then the polygon'''
if killSwitch:
self.poly.Select(ID)
for i in range(self.poly.VertexCount()):
self.points.Select(self.poly.VertexByIndex(i))
self.points.Remove()
self.poly.Remove()
self.mesh.SetMeshEdits(lx.symbol.f_MESHEDIT_GEOMETRY)

lscan.Apply()

'''These error dialogs catch known cases of failures earlier in the process'''
def e_NOCURVE(self):
self.fire('dialog.setup error')
self.fire('dialog.title {Rebuild Curve}')
self.fire('dialog.msg {No curve was found in the current mesh layer.}')
self.fire('dialog.open')