From 2d1368a908a92d462ee737ca92404d331475b262 Mon Sep 17 00:00:00 2001
From: mm00 <github@mm00.me>
Date: Thu, 3 Apr 2025 18:48:21 +0200
Subject: [PATCH] Added directional blur

---
 SDFMapCreator/Program.cs            | 28 +++++++++++++++
 SDFMapCreator/SdfKernels.Kernels.cs | 56 +++++++++++++++++++++++++++++
 SDFMapCreator/SdfKernels.cs         | 30 ++++++++++++++++
 3 files changed, 114 insertions(+)

diff --git a/SDFMapCreator/Program.cs b/SDFMapCreator/Program.cs
index 53b158a..7000caf 100644
--- a/SDFMapCreator/Program.cs
+++ b/SDFMapCreator/Program.cs
@@ -119,6 +119,18 @@ public class Program {
             }
             currStep += stepIncrement;
         }
+        
+        // apply directional blur
+        var iterations = 10;
+        var radius = 3f;
+        var step = .5f;
+        var sigma = 1f;
+        for (int i = 0; i < iterations; i++)
+        {
+            Console.WriteLine($"Applying directional blur {i + 1}/{iterations}...");
+            finalImage = DirectionalBlur(finalImage, ImageMasks[0].Mask, radius, step, sigma);
+        }
+
         finalImage.SaveImage("final.png");
         Console.WriteLine("Done!");
     }
@@ -219,6 +231,22 @@ public class Program {
 
         return new(temp);
     }
+    
+    static Vector3[,] DirectionalBlur(Vector3[,] image, Vector3[,] mask, float radius = 3f, float step = .5f, float sigma = 1f) {
+        var width = (uint)image.GetLength(0);
+        var height = (uint)image.GetLength(1);
+        var output = new Vector3[width, height];
+        
+        var sw = new Stopwatch();
+        sw.Start();
+        
+        kernels.DirectionalBlur(image, mask, out var temp, radius, step, sigma);
+        
+        Console.WriteLine(
+            $"Directional Blur Time: {sw.Elapsed.TotalSeconds:N4}s ({width * height / sw.Elapsed.TotalSeconds:N0} pixels/s)");
+        
+        return temp;
+    }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static float EuclideanDistance(Vector2 a, Vector2 b) =>
diff --git a/SDFMapCreator/SdfKernels.Kernels.cs b/SDFMapCreator/SdfKernels.Kernels.cs
index a10f793..1a54571 100644
--- a/SDFMapCreator/SdfKernels.Kernels.cs
+++ b/SDFMapCreator/SdfKernels.Kernels.cs
@@ -79,5 +79,61 @@ public partial class SdfKernels {
         if(mask[index].X == 0f || mask[index].Y == 0f) return;
         float a = sdfa[index].X; float b = sdfb[index].X;
         gradient[index] = new (a / (a + b));
+
+    private static void DirectionalBlurKernel(Index2D index,
+        ArrayView2D<Vector3, Stride2D.DenseX> image,
+        ArrayView2D<Vector3, Stride2D.DenseX> mask,
+        ArrayView2D<Vector3, Stride2D.DenseX> output,
+        float radius, float step, float sigma,
+        int width, int height
+    )
+    {
+        int x = index.X;
+        int y = index.Y;
+        Vector3 value = image[x, y];
+        Vector3 maskValue = mask[x, y];
+        if (maskValue.X == 0f)
+        {
+            output[x, y] = value;
+            return;
+        }
+
+        var gradient = Vector2.Zero;
+
+        for (int dx = -1; dx <= 1; dx++)
+        {
+            for (int dy = -1; dy <= 1; dy++)
+            {
+                if (x + dx < 0 || x + dx >= width || y + dy < 0 || y + dy >= height) continue;
+                gradient += new Vector2(dx, dy) * image[x + dx, y + dy].X;
+            }
+        }
+
+        if (gradient == Vector2.Zero)
+        {
+            output[x, y] = value;
+            return;
+        }
+
+        gradient = Vector2.Normalize(gradient);
+        float sum = 0;
+
+        // now we follow the direction line and sample the image for length;
+        for (float l = -radius; l <= radius; l += step)
+        {
+            int xOffset = (int)(gradient.X * l);
+            int yOffset = (int)(gradient.Y * l);
+            int xSample = x + xOffset;
+            int ySample = y + yOffset;
+
+            if (xSample < 0 || xSample >= width || ySample < 0 || ySample >= height) continue;
+
+            Vector3 sampleValue = image[xSample, ySample];
+            float weight = MathF.Exp(-l * l / (2f * sigma * sigma));
+            output[x, y] += sampleValue * weight;
+            sum += weight;
+        }
+
+        output[x, y] /= sum;
     }
 }
diff --git a/SDFMapCreator/SdfKernels.cs b/SDFMapCreator/SdfKernels.cs
index 21dd878..5cea7c4 100644
--- a/SDFMapCreator/SdfKernels.cs
+++ b/SDFMapCreator/SdfKernels.cs
@@ -5,6 +5,7 @@ using ILGPU.Runtime;
 using ILGPU.Runtime.CPU;
 using ILGPU.Runtime.Cuda;
 using ILGPU.Runtime.OpenCL;
+using ILGPU.Algorithms;
 
 namespace SDFMapCreator;
 
@@ -18,6 +19,7 @@ public partial class SdfKernels {
             .Cuda()
             .CPU()
             .Math(MathMode.Fast32BitOnly)
+            .EnableAlgorithms()
         );
 
         Console.WriteLine("Reading available accelerators (CUDA only)...");
@@ -157,6 +159,34 @@ public partial class SdfKernels {
         accelerator.Synchronize();
 
         gradient = bufferMask.GetAsArray2D();
+    
+    public void DirectionalBlur(Vector3[,] image, Vector3[,] mask, out Vector3[,] output, float radius = 3f, float step = .5f, float sigma = 1f) {
+        var dev = gpuContext.GetPreferredDevice(preferCPU:false);
+        int width = image.GetLength(0);
+        int height = image.GetLength(1);
+        output = new Vector3[width, height];
+        using Accelerator accelerator = dev.CreateAccelerator(gpuContext);
+
+        using var imageBuffer = accelerator.Allocate2DDenseX<Vector3>(new (width, height));
+        imageBuffer.CopyFromCPU(image);
+
+        using var maskBuffer = accelerator.Allocate2DDenseX<Vector3>(new (width, height));
+        maskBuffer.CopyFromCPU(mask);
+
+        using var outputBuffer = accelerator.Allocate2DDenseX<Vector3>(new (width, height));
+
+        var blurKernel = accelerator.LoadAutoGroupedStreamKernel<Index2D,
+            ArrayView2D<Vector3, Stride2D.DenseX>,
+            ArrayView2D<Vector3, Stride2D.DenseX>,
+            ArrayView2D<Vector3, Stride2D.DenseX>,
+            float, float, float, int, int>(DirectionalBlurKernel);
+
+        blurKernel(new (width, height), imageBuffer.View, maskBuffer.View, outputBuffer.View, 
+            radius, step, sigma, width, height);
+
+        accelerator.Synchronize();
+
+        output = outputBuffer.GetAsArray2D();
     }
     
     private static string GetInfoString(Accelerator a)