path: root/OpenSim/Region/Framework/Scenes/TerrainCompressor.cs

/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* Freely adapted from the Aurora version of the terrain compressor.
 * Copyright (c) Contributors, http://aurora-sim.org/, http://opensimulator.org/
 */

using System;
using System.Reflection;

using log4net;

using OpenSim.Framework;
using OpenSim.Region.Framework;
using OpenSim.Region.Framework.Scenes;

using OpenMetaverse;
using OpenMetaverse.Packets;

namespace OpenSim.Region.ClientStack.LindenUDP
{
    public static class OpenSimTerrainCompressor
    {
//        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

#pragma warning disable 414
        private static string LogHeader = "[TERRAIN COMPRESSOR]";
#pragma warning restore 414

        public const int END_OF_PATCHES = 97;

        private const float OO_SQRT2 = 0.7071067811865475244008443621049f;
        private const int STRIDE = 264;

        private const int ZERO_CODE = 0x0;
        private const int ZERO_EOB = 0x2;
        private const int POSITIVE_VALUE = 0x6;
        private const int NEGATIVE_VALUE = 0x7;

        private static readonly float[] DequantizeTable16 =
            new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

        private static readonly float[] DequantizeTable32 =
            new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

        private static readonly float[] CosineTable16 = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
        //private static readonly float[] CosineTable32 = new float[Constants.TerrainPatchSize * Constants.TerrainPatchSize];
        private static readonly int[] CopyMatrix16 = new int[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
        private static readonly int[] CopyMatrix32 = new int[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

        private static readonly float[] QuantizeTable16 =
            new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

        static OpenSimTerrainCompressor()
        {
            // Initialize the decompression tables
            BuildDequantizeTable16();
            SetupCosines16();
            BuildCopyMatrix16();
            BuildQuantizeTable16();
        }

        // Used to send cloud and wind patches
        public static LayerDataPacket CreateLayerDataPacket(TerrainPatch[] patches, byte type, int pRegionSizeX,
                                                            int pRegionSizeY)
        {
            LayerDataPacket layer = new LayerDataPacket {LayerID = {Type = type}};

            TerrainPatch.GroupHeader header = new TerrainPatch.GroupHeader
                                                  {Stride = STRIDE, PatchSize = Constants.TerrainPatchSize};

            // Should be enough to fit even the most poorly packed data
            byte[] data = new byte[patches.Length*Constants.TerrainPatchSize*Constants.TerrainPatchSize*2];
            BitPack bitpack = new BitPack(data, 0);
            bitpack.PackBits(header.Stride, 16);
            bitpack.PackBits(header.PatchSize, 8);
            bitpack.PackBits(type, 8);

            foreach (TerrainPatch t in patches)
                CreatePatch(bitpack, t.Data, t.X, t.Y, pRegionSizeX, pRegionSizeY);

            bitpack.PackBits(END_OF_PATCHES, 8);

            layer.LayerData.Data = new byte[bitpack.BytePos + 1];
            Buffer.BlockCopy(bitpack.Data, 0, layer.LayerData.Data, 0, bitpack.BytePos + 1);

            return layer;
        }

        // Create a land packet for a single patch.
        public static LayerDataPacket CreateLandPacket(TerrainData terrData, int patchX, int patchY)
        {
            int[] xPieces = new int[1];
            int[] yPieces = new int[1];
            xPieces[0] = patchX;  // patch X dimension
            yPieces[0] = patchY;

            byte landPacketType = (byte)TerrainPatch.LayerType.Land;
            if (terrData.SizeX > Constants.RegionSize || terrData.SizeY > Constants.RegionSize)
            {
                landPacketType = (byte)TerrainPatch.LayerType.LandExtended;
            }

            return CreateLandPacket(terrData, xPieces, yPieces, landPacketType);
        }

        /// <summary>
        ///     Creates a LayerData packet for compressed land data given a full
        ///     simulator heightmap and an array of indices of patches to compress
        /// </summary>
        /// <param name="terrData">
        ///     Terrain data that can result in a meter square heightmap.
        /// </param>
        /// <param name="x">
        ///     Array of indexes in the grid of patches
        ///     for this simulator.
        ///     If creating a packet for multiple patches, there will be entries in
        ///     both the X and Y arrays for each of the patches.
        ///     For example if patches 1 and 17 are to be sent,
        ///     x[] = {1,1} and y[] = {0,1} which specifies the patches at
        ///     indexes <1,0> and <1,1> (presuming the terrain size is 16x16 patches).
        /// </param>
        /// <param name="y">
        ///     Array of indexes in the grid of patches.
        /// </param>
        /// <param name="type"></param>
        /// <param name="pRegionSizeX"></param>
        /// <param name="pRegionSizeY"></param>
        /// <returns></returns>
        public static LayerDataPacket CreateLandPacket(TerrainData terrData, int[] x, int[] y, byte type)
        {
            LayerDataPacket layer = new LayerDataPacket {LayerID = {Type = type}};

            TerrainPatch.GroupHeader header = new TerrainPatch.GroupHeader
                                                  {Stride = STRIDE, PatchSize = Constants.TerrainPatchSize};

            byte[] data = new byte[x.Length * Constants.TerrainPatchSize * Constants.TerrainPatchSize * 2];
            BitPack bitpack = new BitPack(data, 0);
            bitpack.PackBits(header.Stride, 16);
            bitpack.PackBits(header.PatchSize, 8);
            bitpack.PackBits(type, 8);

            for (int i = 0; i < x.Length; i++)
                CreatePatchFromHeightmap(bitpack, terrData, x[i], y[i]);

            bitpack.PackBits(END_OF_PATCHES, 8);

            layer.LayerData.Data = new byte[bitpack.BytePos + 1];
            Buffer.BlockCopy(bitpack.Data, 0, layer.LayerData.Data, 0, bitpack.BytePos + 1);

            return layer;
        }

        // Unused: left for historical reference.
        public static void CreatePatch(BitPack output, float[] patchData, int x, int y, int pRegionSizeX, int pRegionSizeY)
        {
            TerrainPatch.Header header = PrescanPatch(patchData);
            header.QuantWBits = 136;
            if (pRegionSizeX > Constants.RegionSize || pRegionSizeY > Constants.RegionSize)
            {
                header.PatchIDs = (y & 0xFFFF);
                header.PatchIDs += (x << 16);
            }
            else
            {
                header.PatchIDs = (y & 0x1F);
                header.PatchIDs += (x << 5);
            }

            // NOTE: No idea what prequant and postquant should be or what they do

            int wbits;
            int[] patch = CompressPatch(patchData, header, 10, out wbits);
            wbits = EncodePatchHeader(output, header, patch, Constants.RegionSize, Constants.RegionSize, wbits);
            EncodePatch(output, patch, 0, wbits);
        }

        /// <summary>
        ///     Add a patch of terrain to a BitPacker
        /// </summary>
        /// <param name="output">BitPacker to write the patch to</param>
        /// <param name="heightmap">
        ///     Heightmap of the simulator. Presumed to be an sizeX*sizeY array.
        /// </param>
        /// <param name="patchX">
        ///     X offset of the patch to create.
        /// </param>
        /// <param name="patchY">
        ///     Y offset of the patch to create.
        /// </param>
        /// <param name="pRegionSizeX"></param>
        /// <param name="pRegionSizeY"></param>
        public static void CreatePatchFromHeightmap(BitPack output, TerrainData terrData, int patchX, int patchY)
        {
            TerrainPatch.Header header = PrescanPatch(terrData, patchX, patchY);
            header.QuantWBits = 136;

            // If larger than legacy region size, pack patch X and Y info differently.
            if (terrData.SizeX > Constants.RegionSize || terrData.SizeY > Constants.RegionSize)
            {
                header.PatchIDs = (patchY & 0xFFFF);
                header.PatchIDs += (patchX << 16);
            }
            else
            {
                header.PatchIDs = (patchY & 0x1F);
                header.PatchIDs += (patchX << 5);
            }

            // m_log.DebugFormat("{0} CreatePatchFromHeightmap. patchX={1}, patchY={2}, DCOffset={3}, range={4}",
            //                         LogHeader, patchX, patchY, header.DCOffset, header.Range);

            // NOTE: No idea what prequant and postquant should be or what they do
            int wbits;
            int[] patch = CompressPatch(terrData, patchX, patchY, header, 10, out wbits);
            wbits = EncodePatchHeader(output, header, patch, (uint)terrData.SizeX, (uint)terrData.SizeY, wbits);
            EncodePatch(output, patch, 0, wbits);
        }

        private static TerrainPatch.Header PrescanPatch(float[] patch)
        {
            TerrainPatch.Header header = new TerrainPatch.Header();
            float zmax = -99999999.0f;
            float zmin = 99999999.0f;

            for (int i = 0; i < Constants.TerrainPatchSize*Constants.TerrainPatchSize; i++)
            {
                float val = patch[i];
                if (val > zmax) zmax = val;
                if (val < zmin) zmin = val;
            }

            header.DCOffset = zmin;
            header.Range = (int) ((zmax - zmin) + 1.0f);

            return header;
        }

        // Scan the height info we're returning and return a patch packet header for this patch.
        private static TerrainPatch.Header PrescanPatch(TerrainData terrData, int patchX, int patchY)
        {
            TerrainPatch.Header header = new TerrainPatch.Header();
            float zmax = -99999999.0f;
            float zmin = 99999999.0f;

            for (int j = patchY*Constants.TerrainPatchSize; j < (patchY + 1)*Constants.TerrainPatchSize; j++)
            {
                for (int i = patchX*Constants.TerrainPatchSize; i < (patchX + 1)*Constants.TerrainPatchSize; i++)
                {
                    float val = terrData[i, j];
                    if (val > zmax) zmax = val;
                    if (val < zmin) zmin = val;
                }
            }

            header.DCOffset = zmin;
            header.Range = (int)((zmax - zmin) + 1.0f);

            return header;
        }

        public static TerrainPatch.Header DecodePatchHeader(BitPack bitpack)
        {
            TerrainPatch.Header header = new TerrainPatch.Header {QuantWBits = bitpack.UnpackBits(8)};

            // Quantized word bits
            if (header.QuantWBits == END_OF_PATCHES)
                return header;

            // DC offset
            header.DCOffset = bitpack.UnpackFloat();

            // Range
            header.Range = bitpack.UnpackBits(16);

            // Patch IDs (10 bits)
            header.PatchIDs = bitpack.UnpackBits(10);

            // Word bits
            header.WordBits = (uint) ((header.QuantWBits & 0x0f) + 2);

            return header;
        }

        private static int EncodePatchHeader(BitPack output, TerrainPatch.Header header, int[] patch, uint pRegionSizeX,
                                             uint pRegionSizeY, int wbits)
        {
            /*
                    int temp;
                    int wbits = (header.QuantWBits & 0x0f) + 2;
                    uint maxWbits = (uint)wbits + 5;
                    uint minWbits = ((uint)wbits >> 1);
                    int wbitsMaxValue;
        */
            // goal is to determ minimum number of bits to use so all data fits
            /*
                    wbits = (int)minWbits;
                    wbitsMaxValue = (1 << wbits);

                    for (int i = 0; i < patch.Length; i++)
                    {
                        temp = patch[i];
                        if (temp != 0)
                        {
                            // Get the absolute value
                            if (temp < 0) temp *= -1;

         no coments..

                            for (int j = (int)maxWbits; j > (int)minWbits; j--)
                            {
                                if ((temp & (1 << j)) != 0)
                                {
                                    if (j > wbits) wbits = j;
                                    break;
                                }
                            }
 
                            while (temp > wbitsMaxValue)
                                {
                                wbits++;
                                if (wbits == maxWbits)
                                    goto Done;
                                wbitsMaxValue = 1 << wbits;
                                }
                        }
                    }

                Done:

                    //            wbits += 1;
         */
            // better check
            if (wbits > 17)
                wbits = 16;
            else if (wbits < 3)
                wbits = 3;

            header.QuantWBits &= 0xf0;

            header.QuantWBits |= (wbits - 2);

            output.PackBits(header.QuantWBits, 8);
            output.PackFloat(header.DCOffset);
            output.PackBits(header.Range, 16);
            if (pRegionSizeX > Constants.RegionSize || pRegionSizeY > Constants.RegionSize)
                output.PackBits(header.PatchIDs, 32);
            else
                output.PackBits(header.PatchIDs, 10);

            return wbits;
        }

        private static void IDCTColumn16(float[] linein, float[] lineout, int column)
        {
            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                float total = OO_SQRT2*linein[column];

                for (int u = 1; u < Constants.TerrainPatchSize; u++)
                {
                    int usize = u*Constants.TerrainPatchSize;
                    total += linein[usize + column]*CosineTable16[usize + n];
                }

                lineout[Constants.TerrainPatchSize*n + column] = total;
            }
        }

        private static void IDCTLine16(float[] linein, float[] lineout, int line)
        {
            const float oosob = 2.0f/Constants.TerrainPatchSize;
            int lineSize = line*Constants.TerrainPatchSize;

            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                float total = OO_SQRT2*linein[lineSize];

                for (int u = 1; u < Constants.TerrainPatchSize; u++)
                {
                    total += linein[lineSize + u]*CosineTable16[u*Constants.TerrainPatchSize + n];
                }

                lineout[lineSize + n] = total*oosob;
            }
        }

/*
        private static void DCTLine16(float[] linein, float[] lineout, int line)
        {
            float total = 0.0f;
            int lineSize = line * Constants.TerrainPatchSize;

            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                total += linein[lineSize + n];
            }

            lineout[lineSize] = OO_SQRT2 * total;

            int uptr = 0;
            for (int u = 1; u < Constants.TerrainPatchSize; u++)
            {
                total = 0.0f;
                uptr += Constants.TerrainPatchSize;

                for (int n = 0; n < Constants.TerrainPatchSize; n++)
                {
                    total += linein[lineSize + n] * CosineTable16[uptr + n];
                }

                lineout[lineSize + u] = total;
            }
        }
*/

        private static void DCTLine16(float[] linein, float[] lineout, int line)
        {
            // outputs transpose data (lines exchanged with coluns )
            // so to save a bit of cpu when doing coluns
            float total = 0.0f;
            int lineSize = line*Constants.TerrainPatchSize;

            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                total += linein[lineSize + n];
            }

            lineout[line] = OO_SQRT2*total;

            for (int u = Constants.TerrainPatchSize;
                 u < Constants.TerrainPatchSize*Constants.TerrainPatchSize;
                 u += Constants.TerrainPatchSize)
            {
                total = 0.0f;
                for (int ptrn = lineSize, ptru = u; ptrn < lineSize + Constants.TerrainPatchSize; ptrn++,ptru++)
                {
                    total += linein[ptrn]*CosineTable16[ptru];
                }

                lineout[line + u] = total;
            }
        }


        /*
                private static void DCTColumn16(float[] linein, int[] lineout, int column)
                {
                    float total = 0.0f;
        //            const float oosob = 2.0f / Constants.TerrainPatchSize;

                    for (int n = 0; n < Constants.TerrainPatchSize; n++)
                    {
                        total += linein[Constants.TerrainPatchSize * n + column];
                    }

        //            lineout[CopyMatrix16[column]] = (int)(OO_SQRT2 * total * oosob * QuantizeTable16[column]);
                    lineout[CopyMatrix16[column]] = (int)(OO_SQRT2 * total * QuantizeTable16[column]);

                    for (int uptr = Constants.TerrainPatchSize; uptr < Constants.TerrainPatchSize * Constants.TerrainPatchSize; uptr += Constants.TerrainPatchSize)
                    {
                        total = 0.0f;

                        for (int n = 0; n < Constants.TerrainPatchSize; n++)
                        {
                            total += linein[Constants.TerrainPatchSize * n + column] * CosineTable16[uptr + n];
                        }

        //                lineout[CopyMatrix16[Constants.TerrainPatchSize * u + column]] = (int)(total * oosob * QuantizeTable16[Constants.TerrainPatchSize * u + column]);
                        lineout[CopyMatrix16[uptr + column]] = (int)(total * QuantizeTable16[uptr + column]);
                        }
                }

        private static void DCTColumn16(float[] linein, int[] lineout, int column)
        {
            // input columns are in fact stored in lines now

            float total = 0.0f;
//            const float oosob = 2.0f / Constants.TerrainPatchSize;
            int inlinesptr = Constants.TerrainPatchSize*column;

            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                total += linein[inlinesptr + n];
            }

            //            lineout[CopyMatrix16[column]] = (int)(OO_SQRT2 * total * oosob * QuantizeTable16[column]);
            lineout[CopyMatrix16[column]] = (int) (OO_SQRT2*total*QuantizeTable16[column]);

            for (int uptr = Constants.TerrainPatchSize;
                 uptr < Constants.TerrainPatchSize*Constants.TerrainPatchSize;
                 uptr += Constants.TerrainPatchSize)
            {
                total = 0.0f;

                for (int n = inlinesptr, ptru = uptr; n < inlinesptr + Constants.TerrainPatchSize; n++, ptru++)
                {
                    total += linein[n]*CosineTable16[ptru];
                }

//                lineout[CopyMatrix16[Constants.TerrainPatchSize * u + column]] = (int)(total * oosob * QuantizeTable16[Constants.TerrainPatchSize * u + column]);
                lineout[CopyMatrix16[uptr + column]] = (int) (total*QuantizeTable16[uptr + column]);
            }
        }
        */

        private static int DCTColumn16Wbits(float[] linein, int[] lineout, int column, int wbits, int maxwbits)
        {
            // input columns are in fact stored in lines now

            bool dowbits = wbits != maxwbits;
            int wbitsMaxValue = 1 << wbits;

            float total = 0.0f;
            //            const float oosob = 2.0f / Constants.TerrainPatchSize;
            int inlinesptr = Constants.TerrainPatchSize*column;

            for (int n = 0; n < Constants.TerrainPatchSize; n++)
            {
                total += linein[inlinesptr + n];
            }

            //            lineout[CopyMatrix16[column]] = (int)(OO_SQRT2 * total * oosob * QuantizeTable16[column]);
            int tmp = (int) (OO_SQRT2*total*QuantizeTable16[column]);
            lineout[CopyMatrix16[column]] = tmp;

            if (dowbits)
            {
                if (tmp < 0) tmp *= -1;
                while (tmp > wbitsMaxValue)
                {
                    wbits++;
                    wbitsMaxValue = 1 << wbits;
                    if (wbits == maxwbits)
                    {
                        dowbits = false;
                        break;
                    }
                }
            }

            for (int uptr = Constants.TerrainPatchSize;
                 uptr < Constants.TerrainPatchSize*Constants.TerrainPatchSize;
                 uptr += Constants.TerrainPatchSize)
            {
                total = 0.0f;

                for (int n = inlinesptr, ptru = uptr; n < inlinesptr + Constants.TerrainPatchSize; n++, ptru++)
                {
                    total += linein[n]*CosineTable16[ptru];
                }

                tmp = (int) (total*QuantizeTable16[uptr + column]);
                lineout[CopyMatrix16[uptr + column]] = tmp;

                if (dowbits)
                {
                    if (tmp < 0) tmp *= -1;
                    while (tmp > wbitsMaxValue)
                    {
                        wbits++;
                        wbitsMaxValue = 1 << wbits;
                        if (wbits == maxwbits)
                        {
                            dowbits = false;
                            break;
                        }
                    }
                }
            }
            return wbits;
        }

        public static void DecodePatch(int[] patches, BitPack bitpack, TerrainPatch.Header header, int size)
        {
            for (int n = 0; n < size*size; n++)
            {
                // ?
                int temp = bitpack.UnpackBits(1);
                if (temp != 0)
                {
                    // Value or EOB
                    temp = bitpack.UnpackBits(1);
                    if (temp != 0)
                    {
                        // Value
                        temp = bitpack.UnpackBits(1);
                        if (temp != 0)
                        {
                            // Negative
                            temp = bitpack.UnpackBits((int) header.WordBits);
                            patches[n] = temp*-1;
                        }
                        else
                        {
                            // Positive
                            temp = bitpack.UnpackBits((int) header.WordBits);
                            patches[n] = temp;
                        }
                    }
                    else
                    {
                        // Set the rest to zero
                        // TODO: This might not be necessary
                        for (int o = n; o < size*size; o++)
                        {
                            patches[o] = 0;
                        }
                        break;
                    }
                }
                else
                {
                    patches[n] = 0;
                }
            }
        }

        private static void EncodePatch(BitPack output, int[] patch, int postquant, int wbits)
        {
            int maxwbitssize = (1 << wbits) - 1;

            if (postquant > Constants.TerrainPatchSize*Constants.TerrainPatchSize || postquant < 0)
            {
                Logger.Log("Postquant is outside the range of allowed values in EncodePatch()", Helpers.LogLevel.Error);
                return;
            }

            if (postquant != 0) patch[Constants.TerrainPatchSize*Constants.TerrainPatchSize - postquant] = 0;

            for (int i = 0; i < Constants.TerrainPatchSize*Constants.TerrainPatchSize; i++)
            {
                int temp = patch[i];

                if (temp == 0)
                {
                    bool eob = true;

                    for (int j = i; j < Constants.TerrainPatchSize*Constants.TerrainPatchSize - postquant; j++)
                    {
                        if (patch[j] != 0)
                        {
                            eob = false;
                            break;
                        }
                    }

                    if (eob)
                    {
                        output.PackBits(ZERO_EOB, 2);
                        return;
                    }
                    output.PackBits(ZERO_CODE, 1);
                }
                else
                {
                    if (temp < 0)
                    {
                        temp *= -1;

                        if (temp > maxwbitssize) temp = maxwbitssize;

                        output.PackBits(NEGATIVE_VALUE, 3);
                        output.PackBits(temp, wbits);
                    }
                    else
                    {
                        if (temp > maxwbitssize) temp = maxwbitssize;

                        output.PackBits(POSITIVE_VALUE, 3);
                        output.PackBits(temp, wbits);
                    }
                }
            }
        }

        public static float[] DecompressPatch(int[] patches, TerrainPatch.Header header, TerrainPatch.GroupHeader group)
        {
            float[] block = new float[group.PatchSize*group.PatchSize];
            float[] output = new float[group.PatchSize*group.PatchSize];
            int prequant = (header.QuantWBits >> 4) + 2;
            int quantize = 1 << prequant;
            float ooq = 1.0f/quantize;
            float mult = ooq*header.Range;
            float addval = mult*(1 << (prequant - 1)) + header.DCOffset;

            if (group.PatchSize == Constants.TerrainPatchSize)
            {
                for (int n = 0; n < Constants.TerrainPatchSize*Constants.TerrainPatchSize; n++)
                {
                    block[n] = patches[CopyMatrix16[n]]*DequantizeTable16[n];
                }

                float[] ftemp = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

                for (int o = 0; o < Constants.TerrainPatchSize; o++)
                    IDCTColumn16(block, ftemp, o);
                for (int o = 0; o < Constants.TerrainPatchSize; o++)
                    IDCTLine16(ftemp, block, o);
            }
            else
            {
                for (int n = 0; n < Constants.TerrainPatchSize*2*Constants.TerrainPatchSize*2; n++)
                {
                    block[n] = patches[CopyMatrix32[n]]*DequantizeTable32[n];
                }

                Logger.Log("Implement IDCTPatchLarge", Helpers.LogLevel.Error);
            }

            for (int j = 0; j < block.Length; j++)
            {
                output[j] = block[j]*mult + addval;
            }

            return output;
        }

        private static int[] CompressPatch(float[] patchData, TerrainPatch.Header header, int prequant, out int wbits)
        {
            float[] block = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            int wordsize = (prequant - 2) & 0x0f;
            float oozrange = 1.0f/header.Range;
            float range = (1 << prequant);
            float premult = oozrange*range;
            float sub = (1 << (prequant - 1)) + header.DCOffset*premult;

            header.QuantWBits = wordsize;
            header.QuantWBits |= wordsize << 4;

            int k = 0;
            for (int j = 0; j < Constants.TerrainPatchSize; j++)
            {
                for (int i = 0; i < Constants.TerrainPatchSize; i++)
                    block[k++] = patchData[j*Constants.TerrainPatchSize + i]*premult - sub;
            }

            float[] ftemp = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            int[] itemp = new int[Constants.TerrainPatchSize*Constants.TerrainPatchSize];


            int maxWbits = prequant + 5;
            wbits = (prequant >> 1);

            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                DCTLine16(block, ftemp, o);
            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                wbits = DCTColumn16Wbits(ftemp, itemp, o, wbits, maxWbits);

            return itemp;
        }

        private static int[] CompressPatch(float[,] patchData, TerrainPatch.Header header, int prequant, out int wbits)
        {
            float[] block = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            float oozrange = 1.0f/header.Range;
            float range = (1 << prequant);
            float premult = oozrange*range;
            float sub = (1 << (prequant - 1)) + header.DCOffset*premult;
            int wordsize = (prequant - 2) & 0x0f;

            header.QuantWBits = wordsize;
            header.QuantWBits |= wordsize << 4;

            int k = 0;
            for (int j = 0; j < Constants.TerrainPatchSize; j++)
            {
                for (int i = 0; i < Constants.TerrainPatchSize; i++)
                    block[k++] = patchData[j, i]*premult - sub;
            }

            float[] ftemp = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            int[] itemp = new int[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

            int maxWbits = prequant + 5;
            wbits = (prequant >> 1);

            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                DCTLine16(block, ftemp, o);
            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                wbits = DCTColumn16Wbits(ftemp, itemp, o, wbits, maxWbits);

            return itemp;
        }

        private static int[] CompressPatch(TerrainData terrData, int patchX, int patchY, TerrainPatch.Header header,
                                                               int prequant, out int wbits)
        {
            float[] block = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            int wordsize = prequant;
            float oozrange = 1.0f/header.Range;
            float range = (1 << prequant);
            float premult = oozrange*range;
            float sub = (1 << (prequant - 1)) + header.DCOffset*premult;

            header.QuantWBits = wordsize - 2;
            header.QuantWBits |= (prequant - 2) << 4;

            int k = 0;

            int yPatchLimit = patchY >= (terrData.SizeY / Constants.TerrainPatchSize) ?
                            (terrData.SizeY - Constants.TerrainPatchSize) / Constants.TerrainPatchSize : patchY;
            yPatchLimit = (yPatchLimit + 1) * Constants.TerrainPatchSize;

            int xPatchLimit = patchX >= (terrData.SizeX / Constants.TerrainPatchSize) ?
                            (terrData.SizeX - Constants.TerrainPatchSize) / Constants.TerrainPatchSize : patchX;
            xPatchLimit = (xPatchLimit + 1) * Constants.TerrainPatchSize;

            for (int yy = patchY * Constants.TerrainPatchSize; yy < yPatchLimit; yy++)
            {
                for (int xx = patchX * Constants.TerrainPatchSize; xx < xPatchLimit; xx++)
                {
                    block[k++] = terrData[xx, yy] * premult - sub;
                }
            }

            float[] ftemp = new float[Constants.TerrainPatchSize*Constants.TerrainPatchSize];
            int[] itemp = new int[Constants.TerrainPatchSize*Constants.TerrainPatchSize];

            int maxWbits = prequant + 5;
            wbits = (prequant >> 1);

            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                DCTLine16(block, ftemp, o);
            for (int o = 0; o < Constants.TerrainPatchSize; o++)
                wbits = DCTColumn16Wbits(ftemp, itemp, o, wbits, maxWbits);

            return itemp;
        }

        #region Initialization

        private static void BuildDequantizeTable16()
        {
            for (int j = 0; j < Constants.TerrainPatchSize; j++)
            {
                for (int i = 0; i < Constants.TerrainPatchSize; i++)
                {
                    DequantizeTable16[j*Constants.TerrainPatchSize + i] = 1.0f + 2.0f*(i + j);
                }
            }
        }

        private static void BuildQuantizeTable16()
        {
            const float oosob = 2.0f/Constants.TerrainPatchSize;
            for (int j = 0; j < Constants.TerrainPatchSize; j++)
            {
                for (int i = 0; i < Constants.TerrainPatchSize; i++)
                {
//                    QuantizeTable16[j * Constants.TerrainPatchSize + i] = 1.0f / (1.0f + 2.0f * ((float)i + (float)j));
                    QuantizeTable16[j*Constants.TerrainPatchSize + i] = oosob/(1.0f + 2.0f*(i + (float) j));
                }
            }
        }

        private static void SetupCosines16()
        {
            const float hposz = (float) Math.PI*0.5f/Constants.TerrainPatchSize;

            for (int u = 0; u < Constants.TerrainPatchSize; u++)
            {
                for (int n = 0; n < Constants.TerrainPatchSize; n++)
                {
                    CosineTable16[u*Constants.TerrainPatchSize + n] = (float) Math.Cos((2.0f*n + 1.0f)*u*hposz);
                }
            }
        }

        private static void BuildCopyMatrix16()
        {
            bool diag = false;
            bool right = true;
            int i = 0;
            int j = 0;
            int count = 0;

            while (i < Constants.TerrainPatchSize && j < Constants.TerrainPatchSize)
            {
                CopyMatrix16[j*Constants.TerrainPatchSize + i] = count++;

                if (!diag)
                {
                    if (right)
                    {
                        if (i < Constants.TerrainPatchSize - 1) i++;
                        else j++;

                        right = false;
                        diag = true;
                    }
                    else
                    {
                        if (j < Constants.TerrainPatchSize - 1) j++;
                        else i++;

                        right = true;
                        diag = true;
                    }
                }
                else
                {
                    if (right)
                    {
                        i++;
                        j--;
                        if (i == Constants.TerrainPatchSize - 1 || j == 0) diag = false;
                    }
                    else
                    {
                        i--;
                        j++;
                        if (j == Constants.TerrainPatchSize - 1 || i == 0) diag = false;
                    }
                }
            }
        }

        #endregion Initialization
    }
}