Support 3D BC4 and BC5 compressed textures (#1655)

* Support 3D BC4 and BC5 compressed textures

* PR feedback

* Fix some typos

1 files changed, 242 insertions, 0 deletions

diff --git a/Ryujinx.Graphics.Texture/BCnDecoder.cs b/Ryujinx.Graphics.Texture/BCnDecoder.cs
new file mode 100644
index 00000000..398e8358
--- /dev/null
+++ b/Ryujinx.Graphics.Texture/BCnDecoder.cs
@@ -0,0 +1,242 @@
+using Ryujinx.Common;
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Texture
+{
+    public static class BCnDecoder
+    {
+        private const int BlockWidth = 4;
+        private const int BlockHeight = 4;
+
+        public static byte[] DecodeBC4(ReadOnlySpan<byte> data, int width, int height, int depth, int levels, int layers, bool signed)
+        {
+            int size = 0;
+
+            for (int l = 0; l < levels; l++)
+            {
+                size += Math.Max(1, width >> l) * Math.Max(1, height >> l) * Math.Max(1, depth >> l) * layers;
+            }
+
+            byte[] output = new byte[size];
+
+            ReadOnlySpan<ulong> data64 = MemoryMarshal.Cast<byte, ulong>(data);
+
+            Span<byte> rPal = stackalloc byte[8];
+
+            int baseOOffs = 0;
+
+            for (int l = 0; l < levels; l++)
+            {
+                int w = BitUtils.DivRoundUp(width, BlockWidth);
+                int h = BitUtils.DivRoundUp(height, BlockHeight);
+
+                for (int l2 = 0; l2 < layers; l2++)
+                {
+                    for (int z = 0; z < depth; z++)
+                    {
+                        for (int y = 0; y < h; y++)
+                        {
+                            int baseY = y * BlockHeight;
+
+                            for (int x = 0; x < w; x++)
+                            {
+                                int baseX = x * BlockWidth;
+                                int lineBaseOOffs = baseOOffs + baseX;
+
+                                ulong block = data64[0];
+
+                                rPal[0] = (byte)block;
+                                rPal[1] = (byte)(block >> 8);
+
+                                if (signed)
+                                {
+                                    CalculateBC3AlphaS(rPal);
+                                }
+                                else
+                                {
+                                    CalculateBC3Alpha(rPal);
+                                }
+
+                                ulong rI = block >> 16;
+
+                                for (int texel = 0; texel < BlockWidth * BlockHeight; texel++)
+                                {
+                                    int tX = texel & 3;
+                                    int tY = texel >> 2;
+
+                                    if (baseX + tX >= width || baseY + tY >= height)
+                                    {
+                                        continue;
+                                    }
+
+                                    int shift = texel * 3;
+
+                                    byte r = rPal[(int)((rI >> shift) & 7)];
+
+                                    int oOffs = lineBaseOOffs + tY * width + tX;
+
+                                    output[oOffs] = r;
+                                }
+
+                                data64 = data64.Slice(1);
+                            }
+
+                            baseOOffs += width * (baseY + BlockHeight > height ? (height & (BlockHeight - 1)) : BlockHeight);
+                        }
+                    }
+                }
+
+                width  = Math.Max(1, width  >> 1);
+                height = Math.Max(1, height >> 1);
+                depth  = Math.Max(1, depth  >> 1);
+            }
+
+            return output;
+        }
+
+        public static byte[] DecodeBC5(ReadOnlySpan<byte> data, int width, int height, int depth, int levels, int layers, bool signed)
+        {
+            int size = 0;
+
+            for (int l = 0; l < levels; l++)
+            {
+                size += Math.Max(1, width >> l) * Math.Max(1, height >> l) * Math.Max(1, depth >> l) * layers * 2;
+            }
+
+            byte[] output = new byte[size];
+
+            ReadOnlySpan<ulong> data64 = MemoryMarshal.Cast<byte, ulong>(data);
+
+            Span<byte> rPal = stackalloc byte[8];
+            Span<byte> gPal = stackalloc byte[8];
+
+            int baseOOffs = 0;
+
+            for (int l = 0; l < levels; l++)
+            {
+                int w = BitUtils.DivRoundUp(width, BlockWidth);
+                int h = BitUtils.DivRoundUp(height, BlockHeight);
+
+                for (int l2 = 0; l2 < layers; l2++)
+                {
+                    for (int z = 0; z < depth; z++)
+                    {
+                        for (int y = 0; y < h; y++)
+                        {
+                            int baseY = y * BlockHeight;
+
+                            for (int x = 0; x < w; x++)
+                            {
+                                int baseX = x * BlockWidth;
+                                int lineBaseOOffs = baseOOffs + baseX;
+
+                                ulong blockL = data64[0];
+                                ulong blockH = data64[1];
+
+                                rPal[0] = (byte)blockL;
+                                rPal[1] = (byte)(blockL >> 8);
+                                gPal[0] = (byte)blockH;
+                                gPal[1] = (byte)(blockH >> 8);
+
+                                if (signed)
+                                {
+                                    CalculateBC3AlphaS(rPal);
+                                    CalculateBC3AlphaS(gPal);
+                                }
+                                else
+                                {
+                                    CalculateBC3Alpha(rPal);
+                                    CalculateBC3Alpha(gPal);
+                                }
+
+                                ulong rI = blockL >> 16;
+                                ulong gI = blockH >> 16;
+
+                                for (int texel = 0; texel < BlockWidth * BlockHeight; texel++)
+                                {
+                                    int tX = texel & 3;
+                                    int tY = texel >> 2;
+
+                                    if (baseX + tX >= width || baseY + tY >= height)
+                                    {
+                                        continue;
+                                    }
+
+                                    int shift = texel * 3;
+
+                                    byte r = rPal[(int)((rI >> shift) & 7)];
+                                    byte g = gPal[(int)((gI >> shift) & 7)];
+
+                                    int oOffs = (lineBaseOOffs + tY * width + tX) * 2;
+
+                                    output[oOffs + 0] = r;
+                                    output[oOffs + 1] = g;
+                                }
+
+                                data64 = data64.Slice(2);
+                            }
+
+                            baseOOffs += width * (baseY + BlockHeight > height ? (height & (BlockHeight - 1)) : BlockHeight);
+                        }
+                    }
+                }
+
+                width  = Math.Max(1, width  >> 1);
+                height = Math.Max(1, height >> 1);
+                depth  = Math.Max(1, depth  >> 1);
+            }
+
+            return output;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+         private static void CalculateBC3Alpha(Span<byte> alpha)
+        {
+            for (int i = 2; i < 8; i++)
+            {
+                if (alpha[0] > alpha[1])
+                {
+                    alpha[i] = (byte)(((8 - i) * alpha[0] + (i - 1) * alpha[1]) / 7);
+                }
+                else if (i < 6)
+                {
+                    alpha[i] = (byte)(((6 - i) * alpha[0] + (i - 1) * alpha[1]) / 7);
+                }
+                else if (i == 6)
+                {
+                    alpha[i] = 0;
+                }
+                else /* i == 7 */
+                {
+                    alpha[i] = 0xff;
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void CalculateBC3AlphaS(Span<byte> alpha)
+        {
+            for (int i = 2; i < 8; i++)
+            {
+                if ((sbyte)alpha[0] > (sbyte)alpha[1])
+                {
+                    alpha[i] = (byte)(((8 - i) * (sbyte)alpha[0] + (i - 1) * (sbyte)alpha[1]) / 7);
+                }
+                else if (i < 6)
+                {
+                    alpha[i] = (byte)(((6 - i) * (sbyte)alpha[0] + (i - 1) * (sbyte)alpha[1]) / 7);
+                }
+                else if (i == 6)
+                {
+                    alpha[i] = 0x80;
+                }
+                else /* i == 7 */
+                {
+                    alpha[i] = 0x7f;
+                }
+            }
+        }
+    }
+}
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