Solid3d.md

Solid3d Class

Overview

Solid3d represents a 3D volume primitive or ACIS solid in the AutoCAD database. It is the primary class for creating complex 3D geometry using Boolean operations (Union, Subtract, Intersect) and primitives (Box, Sphere, Cylinder, etc.).

Namespace

Autodesk.AutoCAD.DatabaseServices

Inheritance Hierarchy

System.Object
  └─ RXObject
      └─ DBObject
          └─ Entity
              ├─ Solid3d

Key Properties

Property	Type	Description
Mass	double	Volume of the solid.
Area	double	Surface area.
Centroid	Point3d	Center of mass.
MomentsOfInertia	Vector3d	Moments of inertia.

Key Methods

Method	Return Type	Description
CreateBox(double, double, double)	void	Creates a box solid.
CreateSphere(double)	void	Creates a sphere solid.
CreateCylinder(double, double)	void	Creates a cylinder.
CreateExtrudedSolid(Entity, Vector3d, SweepOptions)	void	Extrudes a profile.
BooleanOperation(BooleanOperationType, Solid3d)	void	Performs Union/Subtract/Intersect.
Slice(Plane, bool)	Solid3d	Slices the solid by a plane.

Code Examples

Example 1: Creating a Simple Box

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    BlockTableRecord btr = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord;
    
    Solid3d box = new Solid3d();
    box.CreateBox(10.0, 10.0, 10.0); // 10x10x10 cube
    
    // Position it at 5,5,5
    box.TransformBy(Matrix3d.Displacement(new Vector3d(5, 5, 5)));
    
    btr.AppendEntity(box);
    tr.AddNewlyCreatedDBObject(box, true);
    
    tr.Commit();
}

Example 2: Boolean subtract (Hollow Box)

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    BlockTableRecord btr = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord;
    
    // Outer box
    Solid3d outer = new Solid3d();
    outer.CreateBox(12, 12, 12);
    
    // Inner box
    Solid3d inner = new Solid3d();
    inner.CreateBox(10, 10, 10);
    
    // Use boolean subtraction: Outer - Inner
    outer.BooleanOperation(BooleanOperationType.BoolSubtract, inner);
    
    // Result is a hollow box (if centered)
    // Note: 'inner' is consumed/invalidated by the operation unless you cloned it,
    // but here we just dispose it implicitly or explicitly.
    // Actually, BooleanOperation typically destroys the second operand.
    // You only add 'outer' to the database.
    inner.Dispose();
    
    btr.AppendEntity(outer);
    tr.AddNewlyCreatedDBObject(outer, true);
    
    tr.Commit();
}

Example 3: Extruding a Circle (Cylinder)

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    BlockTableRecord btr = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord;
    
    // Create Profile
    Circle circle = new Circle(Point3d.Origin, Vector3d.ZAxis, 5.0);
    
    // Create Solid
    Solid3d cylinder = new Solid3d();
    cylinder.CreateExtrudedSolid(circle, Vector3d.ZAxis * 10, new SweepOptions());
    
    btr.AppendEntity(cylinder);
    tr.AddNewlyCreatedDBObject(cylinder, true);
    
    tr.Commit();
}

Example 4: Getting Mass Properties

public void LogMassProps(Solid3d solid)
{
    Application.DocumentManager.MdiActiveDocument.Editor.WriteMessage(
        $"\nVolume: {solid.Mass:F2}" +
        $"\nArea: {solid.Area:F2}" +
        $"\nCentroid: {solid.Centroid}"
    );
}

Example 5: Slicing a Solid

Solid3d solid = ...;
Plane slicePlane = new Plane(Point3d.Origin, Vector3d.XAxis); // Slice at X=0

// Perform slice
// solid is modified to be the "negative" side of the plane
// Returns the "positive" side as a new Solid3d
Solid3d otherHalf = solid.Slice(slicePlane, negativeHalfToo: true);

if (otherHalf != null)
{
    // Add other half to database
}

Example 6: Checking for Interference

Solid3d sol1 = ...;
Solid3d sol2 = ...;

bool interference = sol1.CheckInterference(sol2);

if (interference)
{
    // Create interference solid
    Solid3d intersection = sol1.Clone() as Solid3d;
    intersection.BooleanOperation(BooleanOperationType.BoolIntersect, sol2);
    // 'intersection' is now the common volume
}

Example 7: Creating from Region (Revolve)

Region reg = ...; // 2D Profile
Solid3d revSolid = new Solid3d();

// Revolve region 360 degrees around Y axis
revSolid.CreateRevolvedSolid(reg, Point3d.Origin, Vector3d.YAxis, Math.PI * 2, 0.0, new RevolveOptions());

Example 8: Chamfering Edges (Brep)

// Advanced: ACIS edge manipulation often requires Brep API or specific Solid3d methods
// Simple modifications usually done via Boolean ops.
// Direct edge chamfering via API is complex and often involves accessing the internal BRep.

Best Practices

1. Disposal: Solid3d objects consume significant unmanaged memory (ACIS). Always Dispose() them if created in memory and not added to the database.
2. Boolean Ops: The second operand in BooleanOperation is essentially destroyed/consumed. Do not try to reuse it after the operation.
3. Mass Props: Calculating mass properties (Mass, Centroid) can be computationally expensive for complex solids. Cache values if needed.
4. History: Solid history (recording steps) can bloat file size. Check RecordHistory property.

Related Objects

• Region - 2D equivalent.
• Body - Wireframe/Sheet body wrapper.
• Region

References

• Autodesk Solid3d Reference