How to create a Voronoi diagram texture, IJobParallelFor + Burst

.VoronoiTextureBurstJobComponent.md

• euclidean (left), manhattan (right)

VoronoiTextureBurstJobComponent.cs

// web* src = https://gist.github.com/andrew-raphael-lukasik/cc9d61edbbb44ecb4956c6cb69363a8e
using UnityEngine;
using Unity.Mathematics;
using Unity.Jobs;
using Unity.Collections;
using Unity.Profiling;

[ExecuteInEditMode]
public class VoronoiTextureBurstJobComponent : MonoBehaviour
{
	[SerializeField][Min(1)] uint _seed = 769;
	[SerializeField][Range(2,512)] int _width = 300, _height = 300;
	[SerializeField][Range(1,64)] int _numRandomPoints = 3;

	Texture2D _texture;
	NativeList<ushort2> _points;
	uint lastSeedUsed = 0;
	
	void OnValidate ()
	{
		bool inputChanged = false;

		if( !_points.IsCreated )
		{
			_points = new NativeList<ushort2>( Allocator.Persistent );
			inputChanged = true;
		}
		if( _points.Length!=_numRandomPoints )
		{
			_points.Length = _numRandomPoints;
			inputChanged = true;
		}

		if( _texture==null || _texture.width!=_width || _texture.height!=_height )
		{
			if( _texture==null ) DestroyItWillYou( _texture );
			_texture = new Texture2D( _width , _height , TextureFormat.RGBA32 , mipCount:0 , linear:true );
			inputChanged = true;
		}

		if( inputChanged || _seed!=lastSeedUsed )
		{
			lastSeedUsed = _seed;
			var watch = System.Diagnostics.Stopwatch.StartNew();
			var dep = new FillRandomPointsJob{
				TextureWidth	= _width ,
				TextureHeight	= _height ,
				Seed			= _seed ,
				Points			= _points ,
			}.Schedule();
			NativeArray<RGBA32> textureData = _texture.GetRawTextureData<RGBA32>();
			new GenerateVoronoiDiagramJob{
				Points			= _points ,
				TextureWidth	= _width ,
				TextureHeight	= _height ,
				TextureOutput	= textureData ,
			}.Schedule( textureData.Length , _width , dep ).Complete();
			_texture.Apply();
			Debug.Log( $"jobs took {watch.ElapsedMilliseconds} [ms] to complete");
		}
	}

	void OnEnable ()
		=> OnValidate();

	void OnDisable ()
	{
		if( _texture!=null ) DestroyItWillYou(_texture);
		if( _points.IsCreated ) _points.Dispose();
	}

	void OnGUI ()
		=> GUI.DrawTexture( new Rect(0,0,_width,_height) , _texture );

	void DestroyItWillYou ( Object obj )
	{
		if( Application.isPlaying ) Destroy( obj );
		else DestroyImmediate( obj );
	}

	[Unity.Burst.BurstCompile]
	struct FillRandomPointsJob : IJob
	{
		public int TextureWidth, TextureHeight;
		public uint Seed;
		[WriteOnly] public NativeArray<ushort2> Points;
		void IJob.Execute ()
		{
			var rnd = new Unity.Mathematics.Random( Seed );
			int len = Points.Length;
			for( int i=0 ; i<len ; i++ )
				Points[i] = new ushort2{ x=(ushort)rnd.NextInt(TextureWidth) , y=(ushort)rnd.NextInt(TextureHeight) };
		}
	}

	[Unity.Burst.BurstCompile]
	struct GenerateVoronoiDiagramJob : IJobParallelFor
	{
		[ReadOnly] public NativeArray<ushort2> Points;
		public int TextureWidth, TextureHeight;
		[WriteOnly] public NativeArray<RGBA32> TextureOutput;
		void IJobParallelFor.Execute ( int jobIndex )
		{
			float2 pixelPos = new int2{ x=jobIndex%TextureWidth , y=jobIndex/TextureWidth };

			float pointDist = float.MaxValue;
			int pointIndex = -1;
			for( int i=Points.Length-1 ; i!=-1 ; i-- )
			{
				float2 pointPos = new float2{ x=Points[i].x , y=Points[i].y };
				
				float dist = math.lengthsq( pointPos - pixelPos );// dist sq
				
				// float2 vec =  math.abs( pointPos - pixelPos );
				// float dist = vec.x + vec.y;// manhattan distance
				
				if( dist<pointDist )
				{
					pointDist = dist;
					pointIndex = i;
				}

				if( dist<math.max(math.min(TextureWidth*0.01f,TextureHeight*0.01f),1) )
				{
					TextureOutput[jobIndex] = new RGBA32{ r=0 , g=0 , b=0 , a=255 };
					return;
				}
			}

			RGBA32 colorFromCoord;
			{
				ushort2 pointCoord = Points[pointIndex];
				float2 f = new float2{ x=pointCoord.x , y=pointCoord.y } / ( new float2{ x=TextureWidth , y=TextureHeight } - new float2{ x=1 , y=1 } );
				byte r = (byte)( 255*f.x );
				byte g = (byte)( 255*f.y );
				byte b = (byte)( (r+g)%255 );
				colorFromCoord = new RGBA32{ r=r , g=g , b=b , a=255 };
			}
			TextureOutput[jobIndex] = colorFromCoord;
		}
	}

	struct ushort2 { public ushort x, y; }

	struct RGBA32 { public byte r, g, b, a; }

}