The transformation matrix for ModelToSketchSpace can be obtained from the PlanarSketch object. It wouldn’t be too difficult to calculate it ourselves, but a combination of the OriginPointGeometry, PlanarEntityGeometry, AxisEntityGeometry, and AxisIsX properties give us everything we need to compute this matrix.
The function shown below accepts a PlanarSketch object as an argument and returns Matrix object which is required for Model to Sketch Space transformation. Try go through the code reading the comments.
Public Function createModelToSkecthMatrix( _
ByVal sketch As PlanarSketch) As Matrix
‘ get the sketch origin point
Dim origin As Point = sketch.OriginPointGeometry
‘ and the sketch axis
Dim lineAxis As Line = sketch.AxisEntityGeometry
‘ to get the sketch direction
Dim direction As UnitVector = lineAxis.Direction
‘ now the sketch plane
Dim plane As Plane = sketch.PlanarEntityGeometry
‘ to then get the sketch normal (unit vector)
Dim zAxisUnit As UnitVector = plane.Normal
‘ and get the vector
Dim zAxis As Vector = zAxisUnit.AsVector
‘ finally get the X and Y axis according
‘ to the sketch property
Dim xAxis As Vector
Dim yAxis As Vector
If (sketch.AxisIsX) Then
‘ X axis along the sketch direction
xAxis = direction.AsVector
‘ and the Y axis as the cross product X-Z
yAxis = zAxis.CrossProduct(xAxis)
Else
‘ or the Y axis as the sketch direction
yAxis = direction.AsVector
‘ and the X axis as the cross product Y-Z
xAxis = yAxis.CrossProduct(zAxis)
End If
‘ create a blank matrix
Dim coordMatrix As Matrix = sketch.Application. _
TransientGeometry.CreateMatrix
‘ finally set the matrix as a coordinate
‘ system matrix using the calculate data
coordMatrix.SetCoordinateSystem( _
origin, xAxis, yAxis, zAxis)
Return coordMatrix
End Function
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