topic Re: how to extract _AcDb.Surfce isolines in .NET Forum

how to extract _AcDb.Surfce isolines

essam-salah — Tue, 10 Oct 2023 23:58:42 GMT

is it possible to extract Autodesk.Autocad.DatabaseServices.Surface isolines and border using .Net ?

Re: how to extract _AcDb.Surfce isolines

essam-salah — Wed, 11 Oct 2023 01:10:41 GMT

i'm trying to use _AcDb.NurbSurface.GetIsolineAtU(du) after converting my _AcDb.Surface into NurbSurface using mySurface.ConvertToNurbSurface(),

the problem is i can't figure out how calculate du/dv for GetIsolineAtU / GetIsolineAtV .

Re: how to extract _AcDb.Surfce isolines

ActivistInvestor — Wed, 11 Oct 2023 18:39:28 GMT

Have a look at this blog post.

It shows how to do it in native ObjectARX. The only potential problem I see is that the managed Surface class may not expose all of the needed apis, which means that you may need to resort to p/Invoke.

Re: how to extract _AcDb.Surfce isolines

hippe013 — Wed, 11 Oct 2023 21:49:16 GMT

You are on the right track. See below two example commands for extracting the isolines (curve object) from an AutoCAD surface.

I created a rectangle and then converted that rectangle to a plane surface using the PlaneSurf command.

Using the following two commands (U & V) you can extract an isoline by inputting a value. A value of zero is the midpoint of the plane surface. Inputting a positive number goes in one direction while inputting a negative number goes in the other direction. The value inputted is a unit distance from the mid-point, at least in the example of a plane surface.

I hope this helps get you going in the right direction.

<CommandMethod("AcSurfExtractU")> Public Sub CmdAcSurfExtractU() Dim aDoc As Document = Application.DocumentManager.MdiActiveDocument Dim db As Database = aDoc.Database Dim ed As Editor = aDoc.Editor Dim opt As New PromptEntityOptions(vbCrLf & "Select AutoCAD Surface: ") opt.SetRejectMessage(vbCrLf & "Selected entity must be a AutoCAD Surface. Try again.") opt.AddAllowedClass(GetType(Autodesk.AutoCAD.DatabaseServices.Surface), False) Dim res As PromptEntityResult = ed.GetEntity(opt) If res.Status <> PromptStatus.OK Then Exit Sub Using tr As Transaction = db.TransactionManager.StartTransaction Dim surf As Autodesk.AutoCAD.DatabaseServices.Surface = tr.GetObject(res.ObjectId, OpenMode.ForRead) Dim nurbs As Autodesk.AutoCAD.DatabaseServices.NurbSurface() = surf.ConvertToNurbSurface If Not nurbs.Length > 0 Then Exit Sub End If Dim nurb As Autodesk.AutoCAD.DatabaseServices.NurbSurface = nurbs(0) Dim U_dblOpt As New PromptDoubleOptions(vbCrLf & "Enter U Value: ") Dim U_dblRes As PromptDoubleResult = ed.GetDouble(U_dblOpt) If U_dblRes.Status <> PromptStatus.OK Then Exit Sub End If Dim blkTblRec As BlockTableRecord = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) Dim curves As Curve() = nurb.GetIsolineAtU(U_dblRes.Value) For Each crv As Curve In curves blkTblRec.AppendEntity(crv) tr.AddNewlyCreatedDBObject(crv, True) Next tr.Commit() End Using End Sub <CommandMethod("AcSurfExtractV")> Public Sub CmdAcSurfExtractV() Dim aDoc As Document = Application.DocumentManager.MdiActiveDocument Dim db As Database = aDoc.Database Dim ed As Editor = aDoc.Editor Dim opt As New PromptEntityOptions(vbCrLf & "Select AutoCAD Surface: ") opt.SetRejectMessage(vbCrLf & "Selected entity must be a AutoCAD Surface. Try again.") opt.AddAllowedClass(GetType(Autodesk.AutoCAD.DatabaseServices.Surface), False) Dim res As PromptEntityResult = ed.GetEntity(opt) If res.Status <> PromptStatus.OK Then Exit Sub Using tr As Transaction = db.TransactionManager.StartTransaction Dim surf As Autodesk.AutoCAD.DatabaseServices.Surface = tr.GetObject(res.ObjectId, OpenMode.ForRead) Dim nurbs As Autodesk.AutoCAD.DatabaseServices.NurbSurface() = surf.ConvertToNurbSurface If Not nurbs.Length > 0 Then Exit Sub End If Dim nurb As Autodesk.AutoCAD.DatabaseServices.NurbSurface = nurbs(0) Dim V_dblOpt As New PromptDoubleOptions(vbCrLf & "Enter V Value: ") Dim V_dblRes As PromptDoubleResult = ed.GetDouble(V_dblOpt) If V_dblRes.Status <> PromptStatus.OK Then Exit Sub End If Dim blkTblRec As BlockTableRecord = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) Dim curves As Curve() = nurb.GetIsolineAtV(V_dblRes.Value) For Each crv As Curve In curves blkTblRec.AppendEntity(crv) tr.AddNewlyCreatedDBObject(crv, True) Next tr.Commit() End Using End Sub

Re: how to extract _AcDb.Surfce isolines

essam-salah — Wed, 11 Oct 2023 22:31:20 GMT

hi @ActivistInvestor

@ActivistInvestor wrote:
Have a look at this blog post.

It shows how to do it in native ObjectARX. The only potential problem I see is that the managed Surface class may not expose all of the needed apis, which means that you may need to resort to p/Invoke.

yes, i already tried to use this blog post, here is my code so far:

// prompt for _AcDbSurface, and get surfId var db = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Database; using (var tr = db.TransactionManager.StartTransaction()) { var dbSurface = (_AcDb.Surface)tr.GetObject(surfId, _AcDb.OpenMode.ForWrite); // convert to nurb var dbNurbSurfaces = dbSurface.ConvertToNurbSurface(); if (dbNurbSurfaces.Length < 1) { return; } var dbNurbSurface = dbNurbSurfaces[0]; // pNS in original code var uIsoDensity = dbSurface.UIsoLineDensity; var vIsoDensity = dbSurface.VIsoLineDensity; using (var brep = new _AcBr.Brep(dbSurface)) { foreach (var face in brep.Faces) { var pGeSurface = face.Surface; var intervals = pGeSurface.GetEnvelope(); var intervalU = intervals[0]; var intervalV = intervals[1]; // get min/max bounds var boundMinU = intervalU.LowerBound; var boundMaxU = intervalU.UpperBound; var boundMinV = intervalV.LowerBound; var boundMaxV = intervalV.UpperBound; var isClosedInU = pGeSurface.IsClosedInU(tolerance); var isClosedInV = pGeSurface.IsClosedInV(tolerance); var paramIncrU = (boundMaxU - boundMinU) / (isClosedInU ? uIsoDensity : (uIsoDensity + 1)); var paramIncrV = (boundMaxV - boundMinV) / (isClosedInV ? vIsoDensity : (vIsoDensity + 1)); var ucMax = isClosedInU ? uIsoDensity : uIsoDensity + 2; int vcMax = isClosedInV ? vIsoDensity : vIsoDensity + 2; var paramU = boundMinU; for (int uc = 0; uc < ucMax; uc++) { double paramV = boundMinV; for (int vc = 0; vc < vcMax; vc++) { // u lines var uIsoLines = dbNurbSurface.GetIsolineAtU(paramU); foreach (var uCurve in uIsoLines) { uCurve.ColorIndex = 1; // Add uCurve to Current drawing } // v lines var vIsoLines = dbNurbSurface.GetIsolineAtV(paramV); foreach (var vCurve in vIsoLines) { vCurve.ColorIndex = 2; // Add vCurve to Current drawing } paramV += paramIncrV; } paramU += paramIncrU; } } // foreach face end } // brep end // apply changes tr.Commit(); }

but it doesn't work, it always drawy a 96 Spline as straight lines of length 0.095 at origin for every surface i select,

Re: how to extract _AcDb.Surfce isolines

ActivistInvestor — Sat, 14 Oct 2023 20:17:55 GMT

Just for kicks, I copied the C++ code from the original blog post and asked ChatGPT to convert it to C# .

I can't tell you if works, but it looks as though it can at least be useful for reducing some typing.