// Tolerance for detecting near-zero values,
// used to account for floating-point precision errors.
const double ANGLE_EPSILON = 1E-15;
// Checks if a given number is near zero, within a defined tolerance.
public static bool IsNearZero(double num)
{
return num < ANGLE_EPSILON && num > -ANGLE_EPSILON;
}
// Normalizes an angle to the range [0, 2π], correcting for floating-point precision issues.
// This handles small imprecisions when dealing with angles across different architectures.
public static double FixAngle(double angle)
{
const double TWOPI = 2 * Math.PI; // Constant representing 2π (full circle in radians)
double retang;
if (angle - 1.0 == angle) // Check for infinity
angle = 0; // Treat infinity as zero for angles
retang = angle / TWOPI;
retang = (retang - (int)retang) * TWOPI; // Normalize angle within [0, 2π]
// Unify close-to-zero negative values to zero
// to avoid differences across architectures (ARM vs Intel).
if (retang < 0 && IsNearZero(retang))
{
retang = 0.0;
}
if (retang < 0.0)
retang += TWOPI; // Correct for negative angles
if (retang >= TWOPI)
retang -= TWOPI; // Correct for angles exceeding 2π
return retang;
}
// Converts an angle in world coordinates to local coordinates
// based on a given plane (defined by normal and UCS X-direction vectors).
public static double UserToLocalAngle(Vector3d normal, Vector3d ucsXdir)
{
// Transformation matrix from World Coordinate System (WCS) to Local Coordinate System (LCS)
var wcsToLcs = Matrix3d.WorldToPlane(normal);
// Transform the UCS X-direction vector into the local coordinate system
var xDir = ucsXdir;
xDir.TransformBy(wcsToLcs);
// Calculate the angle in the local plane using Atan2
var angle = Math.Atan2(xDir.Y, xDir.X);
// Normalize the angle using FixAngle to ensure it is within [0, 2π]
return FixAngle(angle);
}
// Command method to test dimensioning of ordinates in AutoCAD
[CommandMethod("TstDimOrdinate")]
public static void TestDimOrdinate()
{
// Get the active AutoCAD document
var doc = Application.DocumentManager.MdiActiveDocument;
if (doc == null) return;
var db = doc.Database; // Get the database of the active document
var ed = doc.Editor; // Get the editor (for user interaction)
// Start a transaction to modify the database
using (var tr = db.TransactionManager.StartTransaction())
{
// Open the block table and the model space block table record for writing
var bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
var btr = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite);
// Create a new UCS based on specified vectors
var ucs = new CoordinateSystem3d(Point3d.Origin, new Vector3d(1, 1, 0), new Vector3d(-1, 1, 0));
// Open the UCS table for reading
var ucsTbl = (UcsTable)tr.GetObject(db.UcsTableId, OpenMode.ForRead);
UcsTableRecord ucstr;
// Check if the UCS named "TestUcs" already exists, if not, create it
if (!ucsTbl.Has("TestUcs"))
{
ucstr = new UcsTableRecord
{
Name = "TestUcs" // Name the UCS "TestUcs"
};
// Open the UCS table for writing and add the new UCS
tr.GetObject(db.UcsTableId, OpenMode.ForWrite);
ucsTbl.Add(ucstr);
tr.AddNewlyCreatedDBObject(ucstr, true);
}
else
{
// Retrieve the existing UCS if "TestUcs" already exists
ucstr = (UcsTableRecord)tr.GetObject(ucsTbl["TestUcs"], OpenMode.ForWrite);
}
// Set UCS origin and axes
ucstr.Origin = Point3d.Origin;
ucstr.XAxis = new Vector3d(1, 1, 0);
ucstr.YAxis = new Vector3d(-1, 1, 0);
// Get the active viewport and configure the UCS icon to display at the origin
var vptr = (ViewportTableRecord)tr.GetObject(doc.Editor.ActiveViewportId, OpenMode.ForWrite);
vptr.IconAtOrigin = true;
vptr.IconEnabled = true;
// Set the current UCS to the newly created or retrieved UCS
vptr.SetUcs(ucstr.ObjectId);
doc.Editor.UpdateTiledViewportsFromDatabase();
// Prompt the user to input two points
PromptPointResult pPtRes;
PromptPointOptions pPtOpts = new PromptPointOptions("");
Point3d[] point3Ds = new Point3d[2];
for (int i = 0; i < 2; i++)
{
pPtOpts.Message = $"\nEnter point {i + 1}: ";
pPtRes = doc.Editor.GetPoint(pPtOpts);
if (pPtRes.Status != PromptStatus.OK)
{
doc.Editor.WriteMessage("\nPoint input was canceled or invalid.");
break;
}
point3Ds[i] = pPtRes.Value; // Store the entered points
}
// Transform the input points to the current UCS
Matrix3d activeUCS = ed.CurrentUserCoordinateSystem;
Point3d ucsDp = point3Ds[0].TransformBy(activeUCS);
Point3d ucsLp = point3Ds[1].TransformBy(activeUCS);
// Calculate the angle of rotation for the ordinate dimension
double rotation = UserToLocalAngle(activeUCS.CoordinateSystem3d.Zaxis, activeUCS.CoordinateSystem3d.Xaxis);
// Create a new Ordinate Dimension with the calculated properties
OrdinateDimension ordDim = new OrdinateDimension
{
DefiningPoint = ucsDp,
LeaderEndPoint = ucsLp,
Normal = activeUCS.CoordinateSystem3d.Xaxis.CrossProduct(activeUCS.CoordinateSystem3d.Yaxis),
UsingXAxis = false,
DimensionStyle = db.Dimstyle,
HorizontalRotation = -rotation,
ColorIndex = 1
};
ordDim.SetDatabaseDefaults();
btr.AppendEntity(ordDim);
tr.AddNewlyCreatedDBObject(ordDim, true);
// Commit the transaction to finalize changes
tr.Commit();
}
}
