How can we define a Coordinate system with X axis point along a direction vector between two nodes

Erik Kostson

Say we have two nodes, 1, and 2. Using scripting, how can one define a Coordinate system with X axis point along a direction vector between two nodes (origin on 1st node)?

Erik Kostson

There are many ways of doing this, but one sample example below , uses 2 named selections (node 1 and 2) and the difference vector between them giving the direction of the X-axis.

This is just an example and can be used and tailored perhaps as needed to suit purpose:

model=ExtAPI.DataModel.Project.Model # refer to Model
analysis = model.Analyses[0]
solution = analysis.Solution

##get 2 NS node 1 and 2
ncs1=ExtAPI.DataModel.GetObjectsByName("MYNCS1")[0]
mncs1=ncs1.Location.Ids
ncs2=ExtAPI.DataModel.GetObjectsByName("MYNCS2")[0]
mncs2=ncs2.Location.Ids

##get mesh nodes of NS
MeshData=ExtAPI.DataModel.MeshDataByName("Global")
node1= MeshData.NodeById(mncs1[0])
node2= MeshData.NodeById(mncs2[0])

## vector = node1-node2
vec=[]
vec[0]=node2.X-node1.X
vec[1]=node2.Y-node1.Y
vec[2]=node2.Z-node1.Z

## define UCS
testCS = ExtAPI.DataModel.Project.Model.CoordinateSystems.AddCoordinateSystem()
testCS.CoordinateSystemType = CoordinateSystemTypeEnum.Cartesian
testCS.OriginX = Quantity(node1.X,"m")
testCS.OriginY = Quantity(node1.Y,"m")
testCS.OriginZ = Quantity(node1.Z,"m")
testCS.PrimaryAxisDirection=Ansys.ACT.Math.Vector3D(vec[0],vec[1],vec[2])

Another way is by selecting to nodes graphically (1st node selection is the origin, and 2nd node is used together with 1st for the alignment):

model=ExtAPI.DataModel.Project.Model # refer to Model
analysis = model.Analyses[0]
solution = analysis.Solution

cursel=ExtAPI.SelectionManager.CurrentSelection.Ids
selectionor = ExtAPI.SelectionManager.CreateSelectionInfo(SelectionTypeEnum.MeshNodes)
selectionor.Ids=[cursel[0]] # first node is origin

testCS = ExtAPI.DataModel.Project.Model.CoordinateSystems.AddCoordinateSystem()

testCS.CoordinateSystemType = CoordinateSystemTypeEnum.Cartesian
testCS.OriginLocation = selectionor



selection = ExtAPI.SelectionManager.CreateSelectionInfo(SelectionTypeEnum.MeshNodes)
selection.Ids=cursel # both nodes needed for x-axis def.

testCS.PrimaryAxisDefineBy=CoordinateSystemAlignmentType.Associative
testCS.PrimaryAxisLocation=selection

Finally the above example can be extended to give some guidelines to the user on how to use it (e.g., to select 2 nodes, etc. - this is done via a text message box)

import clr
clr.AddReference('System.Windows.Forms')
from System.Windows.Forms import MessageBox


model=ExtAPI.DataModel.Project.Model # refer to Model
analysis = model.Analyses[0]
solution = analysis.Solution

cursel=ExtAPI.SelectionManager.CurrentSelection.Ids
selection = ExtAPI.SelectionManager.CreateSelectionInfo(SelectionTypeEnum.MeshNodes)
selection.Ids=cursel # both nodes needed for x-axis def.


if len(selection.Ids)==2:
    selectionor = ExtAPI.SelectionManager.CreateSelectionInfo(SelectionTypeEnum.MeshNodes)
    selectionor.Ids=[cursel[0]] # first node is origin

    testCS = ExtAPI.DataModel.Project.Model.CoordinateSystems.AddCoordinateSystem()
    testCS.CoordinateSystemType = CoordinateSystemTypeEnum.Cartesian
    testCS.OriginLocation = selectionor

    selection.Ids=cursel # both nodes needed for x-axis def.

    testCS.PrimaryAxisDefineBy=CoordinateSystemAlignmentType.Associative
    testCS.PrimaryAxisLocation=selection
else:
    MessageBox.Show('We need to select 2 nodes. 1st node is the CS origin and 2nd is used for the alignmnet of the CS x-axis')