PicoGK__Interop.cs

//
// SPDX-License-Identifier: Apache-2.0
//
// PicoGK ("peacock") is a compact software kernel for computational geometry,
// specifically for use in Computational Engineering Models (CEM).
//
// For more information, please visit https://picogk.org
// 
// PicoGK is developed and maintained by LEAP 71 - © 2023 by LEAP 71
// https://leap71.com
//
// Computational Engineering will profoundly change our physical world in the
// years ahead. Thank you for being part of the journey.
//
// We have developed this library to be used widely, for both commercial and
// non-commercial projects alike. Therefore, we have released it under a 
// permissive open-source license.
//
// The foundation of PicoGK is a thin layer on top of the powerful open-source
// OpenVDB project, which in turn uses many other Free and Open Source Software
// libraries. We are grateful to be able to stand on the shoulders of giants.
//
// LEAP 71 licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with the
// License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, THE SOFTWARE IS
// PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED.
//
// See the License for the specific language governing permissions and
// limitations under the License.   
//

using System;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Text;

namespace PicoGK
{
    // private interfaces to external PicoGK Runtime library

    public partial class Library
    {
        public const int nStringLength = 255;

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Library_Init", CharSet = CharSet.Ansi)]
        private static extern void _Init(float fVoxelSizeMM);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Library_GetName", CharSet = CharSet.Ansi)]
        private static extern void _GetName(StringBuilder psz);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Library_GetVersion", CharSet = CharSet.Ansi)]
        private static extern void _GetVersion(StringBuilder psz);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Library_GetBuildInfo", CharSet = CharSet.Ansi)]
        private static extern void _GetBuildInfo(StringBuilder psz);
    }

    public partial class Mesh : IDisposable
    {
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_hCreate")]
        internal static extern IntPtr _hCreate();

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_hCreateFromVoxels")]
        internal static extern IntPtr _hCreateFromVoxels(IntPtr hVoxels);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_bIsValid")]
        private static extern bool _IsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_nAddVertex")]
        private static extern int _nAddVertex(IntPtr hThis,
                                                in Vector3 V);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_nVertexCount")]
        private static extern int _nVertexCount(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_GetVertex")]
        private static extern void _GetVertex(IntPtr hThis,
                                                int nVertex,
                                                ref Vector3 V);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_nAddTriangle")]
        private static extern int _nAddTriangle(IntPtr hThis,
                                                    in Triangle T);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_nTriangleCount")]
        private static extern int _nTriangleCount(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_GetTriangle")]
        private static extern void _GetTriangle(    IntPtr hThis,
                                                    int nTriangle,
                                                    ref Triangle T);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_GetTriangleV")]
        private static extern void _GetTriangleV(   IntPtr hThis,
                                                    int nTriangle,
                                                    ref Vector3 vecA,
                                                    ref Vector3 vecB,
                                                    ref Vector3 vecC);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Mesh_GetBoundingBox")]
        private static extern void _GetBoundingBox( IntPtr hThis,
                                                    ref BBox3 oBBox);

        // Dispose Pattern

        ~Mesh()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        bool            m_bDisposed = false;
        internal IntPtr m_hThis     = IntPtr.Zero;

    }

    public partial class Lattice : IDisposable
    {
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Lattice_hCreate")]
        internal static extern IntPtr _hCreate();

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Lattice_bIsValid")]
        private static extern bool _bIsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Lattice_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Lattice_AddSphere")]
        private static extern void _AddSphere(  IntPtr      hThis,
                                                in Vector3  vecCenter,
                                                float       fRadius);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Lattice_AddBeam")]
        private static extern void _AddBeam(    IntPtr      hThis,
                                                in Vector3  vecA,
                                                in Vector3  vecB,
                                                float       fRadiusA,
                                                float       fRadiusB,
                                                bool        bRoundCap);

        // Dispose Pattern

        ~Lattice()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        bool            m_bDisposed = false;
        internal IntPtr m_hThis     = IntPtr.Zero;
    }

    public partial class Voxels : IDisposable
    {
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_hCreate")]
        internal static extern IntPtr _hCreate();

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_hCreateCopy")]
        internal static extern IntPtr _hCreateCopy(IntPtr hSource);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_bIsValid")]
        private static extern bool _bIsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_BoolAdd")]
        private static extern void _BoolAdd(    IntPtr hThis,
                                                IntPtr hOther);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_BoolSubtract")]
        private static extern void _BoolSubtract(   IntPtr hThis,
                                                    IntPtr hOther);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_BoolIntersect")]
        private static extern void _BoolIntersect(  IntPtr hThis,
                                                    IntPtr hOther);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_BoolAddSmooth")]
        private static extern void _BoolAddSmooth(  IntPtr hThis,
                                                    IntPtr hOther,
                                                    float fSmoothDistance);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_Offset")]
        private static extern void _Offset( IntPtr hThis,
                                            float fOffset);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_DoubleOffset")]
        private static extern void _DoubleOffset(   IntPtr hThis,
                                                    float fOffset1,
                                                    float fOffset2);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_TripleOffset")]
        private static extern void _TripleOffset(   IntPtr hThis,
                                                    float fOffset);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_RenderMesh")]
        private static extern void _RenderMesh( IntPtr hThis,
                                                IntPtr hMesh);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        private delegate float CallbackImplicitDistance(in Vector3 vec);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_RenderImplicit")]
        private static extern void _RenderImplicit( IntPtr hThis,
                                                    in BBox3 oBounds,
                                                    CallbackImplicitDistance Callback);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_IntersectImplicit")]
        private static extern void _IntersectImplicit(  IntPtr hThis,
                                                        CallbackImplicitDistance Callback);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_RenderLattice")]
        private static extern void _RenderLattice(  IntPtr hThis,
                                                    IntPtr hLattice);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_ProjectZSlice")]
        private static extern void _ProjectZSlice(  IntPtr hThis,
                                                    float fStartX,
                                                    float fEndX);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_bIsInside")]
        private static extern bool _bIsInside(      IntPtr hThis,
                                                    in Vector3 vecTestPoint);


        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_bIsEqual")]
        private static extern bool _bIsEqual(   IntPtr hThis,
                                                IntPtr hOther);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_CalculateProperties")]
        private extern static void _CalculateProperties(    IntPtr hThis,
                                                            out float pfVolume,
                                                            ref BBox3 oBBox);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_GetSurfaceNormal")]
        private extern static void _GetSurfaceNormal(IntPtr hThis,
                                                        in  Vector3 vecSurfacePoint,
                                                        ref Vector3 vecSurfaceNormal);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_bClosestPointOnSurface")]
        private extern static bool _bClosestPointOnSurface( IntPtr hThis,
                                                            in  Vector3 vecSearch,
                                                            ref Vector3 vecSurfacePoint);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_bRayCastToSurface")]
        private extern static bool _bRayCastToSurface(  IntPtr hThis,
                                                        in  Vector3 vecSearch,
                                                        in  Vector3 vecNormal,
                                                        ref Vector3 vecSurfacePoint);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_GetVoxelDimensions")]
        private extern static void _GetVoxelDimensions( IntPtr hThis,
                                                        out int nXSize,
                                                        out int nYSize,
                                                        out int nZSize);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Voxels_GetSlice")]
        private extern static void _GetVoxelSlice(  IntPtr hThis,
                                                    int nZSlice,
                                                    IntPtr afBuffer);

        // Dispose Pattern

        ~Voxels()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        bool            m_bDisposed = false;
        internal IntPtr m_hThis     = IntPtr.Zero;
    }

    public partial class PolyLine : IDisposable
    {
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_hCreate")]
        public static extern IntPtr _hCreate(in ColorFloat clr);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_bIsValid")]
        private static extern bool _bIsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_nAddVertex")]
        private static extern int _nAddVertex(  IntPtr hThis,
                                                in Vector3 vec);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_nVertexCount")]
        private static extern int _nVertexCount(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_GetVertex")]
        private static extern void _GetVertex(  IntPtr hThis,
                                                int nIndex,
                                                ref Vector3 vec);


        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PolyLine_GetColor")]
        private static extern void _GetColor(   IntPtr hThis,
                                                ref ColorFloat clr);

        // Dispose Pattern

        ~PolyLine()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        bool            m_bDisposed = false;
        internal IntPtr m_hThis     = IntPtr.Zero;
    }

    public partial class Viewer : IDisposable
    {
        // Define delegates for the callback functions
        [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        public delegate void InfoCallback(  string  strMessage,
                                            bool    bFatalError);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void UpdateCallback(    IntPtr          hViewer,
                                                in Vector2      vecViewport,
                                                ref ColorFloat  clrBackground,
                                                ref Matrix4x4   matModelViewProjection,
                                                ref Matrix4x4   matModelTransform,
                                                ref Matrix4x4   matStatic,
                                                ref Vector3     vecEyePosition,
                                                ref Vector3     vecEyeStatic);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void KeyPressedCallback(    IntPtr  hViewer,
                                                    int     iKey,
                                                    int     iScancode,
                                                    int     iAction,
                                                    int     iModifiers);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void MouseMovedCallback(    IntPtr      poViewer,
                                                    in Vector2  vecMousePos);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void MouseButtonCallback(   IntPtr  hViewer,
                                                    int         iButton,
                                                    int         iAction,
                                                    int         iModifiers,
                                                    in Vector2  vecMousePos);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void ScrollWheelCallback(   IntPtr      hViewer,
                                                    in Vector2  vecScrollWheel,
                                                    in Vector2  vecMousePos);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate void WindowSizelCallback(   IntPtr hViewer,
                                                    in Vector2 vecWindowSize);

        // Define the P/Invoke signature for Viewer_hCreate
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_hCreate", CharSet = CharSet.Ansi)]
        public static extern IntPtr _hCreate(   string              strWindowTitle,
                                                in Vector2          vecSize,
                                                InfoCallback        fnInfoCallback,
                                                UpdateCallback      fnUpdateCallback,
                                                KeyPressedCallback  fnKeyPressedCallback,
                                                MouseMovedCallback  fnMouseMoveCallback,
                                                MouseButtonCallback fnMouseButtonCallback,
                                                ScrollWheelCallback fnScrollWheelCallback,
                                                WindowSizelCallback fnWindowSizeCallback);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_bIsValid")]
        private static extern bool _bIsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_RequestUpdate")]
        private static extern void _RequestUpdate(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_bPoll")]
        private static extern bool _bPoll(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_RequestScreenShot")]
        private static extern bool _RequestScreenShot(  IntPtr hThis,
                                                        string strScreenShotPath);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_bLoadLightSetup")]
        private static extern bool _bLoadLightSetup(    IntPtr  hThis,
                                                        byte [] abyDiffuseDdsBuffer,
                                                        int     nDiffuseSize,
                                                        byte [] pSpecularDdsBuffer,
                                                        int     nSpecularSize);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_RequestClose")]
        private static extern void _RequestClose(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_AddMesh")]
        private static extern void _AddMesh(    IntPtr  hThis,
                                                int     nGroup,
                                                IntPtr  hMesh);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_RemoveMesh")]
        private static extern void _RemoveMesh( IntPtr hThis,
                                                IntPtr hMesh);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_AddPolyLine")]
        private static extern void _AddPolyLine(    IntPtr hThis,
                                                    int nGroupID,
                                                    IntPtr hPolyLine);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_RemovePolyLine")]
        private static extern void _RemovePolyLine( IntPtr hThis,
                                                    IntPtr hPolyLine);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_SetGroupVisible")]
        private static extern void _SetGroupVisible(    IntPtr  hThis,
                                                        int     nGroupID,
                                                        bool    bVisible);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_SetGroupStatic")]
        private static extern void _SetGroupStatic( IntPtr hThis,
                                                    int nGroupID,
                                                    bool bStatic);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_SetGroupMaterial")]
        private static extern void _SetGroupMaterial(   IntPtr          hThis,
                                                        int             nGroupID,
                                                        in ColorFloat   clr,
                                                        float           fMetallic,
                                                        float           fRoughness);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "Viewer_SetGroupMatrix")]
        private static extern void _SetGroupMatrix( IntPtr          hThis,
                                                    int             nGroupID,
                                                    in Matrix4x4    mat);

        // Dispose Pattern

        ~Viewer()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        InfoCallback        m_fnInfoCB;
        UpdateCallback      m_fnUpdateCB;
        KeyPressedCallback  m_fnKeyPressedCB;
        MouseMovedCallback  m_fnMouseMovedCB;
        MouseButtonCallback m_fnMouseButtonCB;
        ScrollWheelCallback m_fnScrollWheelCB;
        WindowSizelCallback m_fnWindowSizeCB;

        bool    m_bDisposed = false;
        IntPtr  m_hThis     = IntPtr.Zero;
    }

    public partial class OpenVdbFile : IDisposable
    {
        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_hCreate")]
        public static extern IntPtr _hCreate();

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_hCreateFromFile", CharSet = CharSet.Ansi)]
        private static extern IntPtr _hCreateFromFile(string strFile);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_bIsValid")]
        private static extern bool _bIsValid(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_Destroy")]
        private static extern void _Destroy(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_bSaveToFile", CharSet = CharSet.Ansi)]
        private static extern bool _bSaveToFile(    IntPtr hThis,
                                                    string strFileName);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_hGetVoxels")]
        private static extern IntPtr _hGetVoxels(   IntPtr hThis,
                                                    int nIndex);


        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_nAddVoxels", CharSet = CharSet.Ansi)]
        private static extern int _nAddVoxels(  IntPtr hThis,
                                                string strFieldName,
                                                IntPtr hVoxels);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_nFieldCount")]
        private static extern int _nFieldCount(IntPtr hThis);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_GetFieldName", CharSet = CharSet.Ansi)]
        private static extern void _GetFieldName(   IntPtr hThis,
                                                    int nIndex,
                                                    StringBuilder psz);

        [DllImport(Config.strPicoGKLib, CallingConvention = CallingConvention.Cdecl, EntryPoint = "VdbFile_nFieldType")]
        private static extern int _nFieldType(  IntPtr hThis,
                                                int nIndex);

        // Dispose Pattern

        ~OpenVdbFile()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            // Dispose of unmanaged resources.
            Dispose(true);
            // Suppress finalization.
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool bDisposing)
        {
            if (m_bDisposed)
            {
                return;
            }

            if (bDisposing)
            {
                // dispose managed state (managed objects).
                // Nothing to do in this class
            }

            if (m_hThis != IntPtr.Zero)
            {
                _Destroy(m_hThis);
                m_hThis = IntPtr.Zero;
            }

            m_bDisposed = true;
        }

        bool m_bDisposed = false;
        internal IntPtr m_hThis = IntPtr.Zero;
    }
}