- added shadow support and a demo scene for it

- renamed some shaders

Assets/SpriteLightKit/Shaders/SpriteLightKit-Shadowed.shader

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+// note that the sprite must have it's pivot in the center for this to work
+Shader "prime[31]/Sprite Light Kit/Shadowed"
+{
+	Properties
+	{
+		[PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
+		_Color ("Tint", Color) = (1,1,1,1)
+		_ShadowColor ( "Shadow Color", Color ) = ( 0, 0, 0.2, 0.9 )
+		[MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
+
+		_HorizontalSkew ( "Horizontal Skew", Float ) = 0
+		_VerticalScale ( "Vertical Scale", Float ) = 1
+		_VerticalOffset ( "Vertical Offset", Float ) = 0
+
+		_HorizontalTranslation ( "Horizontal Translation", Float ) = 0
+		_VerticalTranslation ( "Vertical Translation", Float ) = 0
+	}
+
+
+	SubShader
+	{
+		Tags
+		{ 
+			"Queue" = "Transparent" 
+			"IgnoreProjector" = "True" 
+			"RenderType" = "Transparent" 
+			"PreviewType" = "Plane"
+			"CanUseSpriteAtlas" = "True"
+		}
+
+		Cull Off
+		Lighting Off
+		ZWrite Off
+		Fog { Mode Off }
+		Blend One OneMinusSrcAlpha
+
+		Pass
+		{
+CGPROGRAM
+#pragma vertex vert
+#pragma fragment frag
+#pragma multi_compile DUMMY PIXELSNAP_ON
+#include "UnityCG.cginc"
+
+struct appdata_t
+{
+	float4 vertex   : POSITION;
+	float4 color    : COLOR;
+	float2 texcoord : TEXCOORD0;
+};
+
+struct v2f
+{
+	float4 vertex   : SV_POSITION;
+	fixed4 color    : COLOR;
+	half2 texcoord  : TEXCOORD0;
+};
+
+sampler2D _MainTex;
+fixed4 _Color;
+fixed4 _ShadowColor;
+float _HorizontalSkew;
+float _VerticalScale;
+float _VerticalOffset;
+float _HorizontalTranslation;
+float _VerticalTranslation;
+
+
+v2f vert( appdata_t IN )
+{
+	v2f OUT;
+	OUT.texcoord = IN.texcoord;
+
+	float4x4 transformMatrix = float4x4
+	(
+		1, _HorizontalSkew, 0, _HorizontalTranslation,
+		0, _VerticalScale, 0, _VerticalTranslation,
+		0, 0, 1, 0,
+		0, _VerticalOffset, 0, 1
+	);
+
+	float4 skewedVertex = mul( transformMatrix, IN.vertex );
+	OUT.vertex = mul( UNITY_MATRIX_MVP, skewedVertex );
+
+	#ifdef PIXELSNAP_ON
+	OUT.vertex = UnityPixelSnap( OUT.vertex );
+	#endif
+
+	return OUT;
+}
+
+fixed4 frag( v2f IN ) : SV_Target
+{
+	fixed4 c = tex2D( _MainTex, IN.texcoord );
+	return c.a * _ShadowColor;
+}
+ENDCG
+		} // end Pass
+
+
+
+Pass
+{
+
+CGPROGRAM
+#pragma vertex vert
+#pragma fragment frag
+#pragma multi_compile DUMMY PIXELSNAP_ON
+#include "UnityCG.cginc"
+
+struct appdata_t
+{
+	float4 vertex   : POSITION;
+	float4 color    : COLOR;
+	float2 texcoord : TEXCOORD0;
+};
+
+struct v2f
+{
+	float4 vertex   : SV_POSITION;
+	fixed4 color    : COLOR;
+	half2 texcoord  : TEXCOORD0;
+};
+
+fixed4 _Color;
+
+v2f vert(appdata_t IN)
+{
+	v2f OUT;
+	OUT.vertex = mul( UNITY_MATRIX_MVP, IN.vertex );
+	OUT.texcoord = IN.texcoord;
+	OUT.color = IN.color * _Color;
+	#ifdef PIXELSNAP_ON
+	OUT.vertex = UnityPixelSnap( OUT.vertex );
+	#endif
+
+	return OUT;
+}
+
+sampler2D _MainTex;
+
+fixed4 frag(v2f IN) : SV_Target
+{
+	fixed4 c = tex2D( _MainTex, IN.texcoord ) * IN.color;
+	c.rgb *= c.a;
+	return c;
+}
+ENDCG
+} // end pass
+
+
+
+
+	} // end SubShader
+}

Assets/SpriteLightKit/Shadows/SpriteLightKitLightManager.cs

@@ -0,0 +1,72 @@
+using UnityEngine;
+using System.Collections.Generic;
+
+
+namespace Prime31
+{
+	public class SpriteLightKitLightManager : MonoBehaviour
+	{
+		List<Vector3> _spriteLightPositions = new List<Vector3>();
+
+
+		void Awake()
+		{
+			var slk = FindObjectOfType<SpriteLightKit>();
+
+			var allGOs = FindObjectsOfType<GameObject>();
+			for( var i = 0; i < allGOs.Length; i++ )
+			{
+				if( ( slk.lightLayer.value & 1 << allGOs[i].layer ) != 0 )
+				{
+					var pos = allGOs[i].transform.position;
+					pos.z = 0f;
+					_spriteLightPositions.Add( pos );
+				}
+			}
+		}
+
+
+		/// <summary>
+		/// returns the weighted average position of any lights within range or the original position passed in if everything
+		/// is further than maxDistance
+		/// </summary>
+		/// <returns>The nearest light.</returns>
+		/// <param name="position">Position.</param>
+		/// <param name="maxDistance">Max distance.</param>
+		public Vector3 getAffectedAverageLightPos( Vector3 position, float maxSqrDistance )
+		{
+			position.z = 0;
+
+			// we want the weighted average position of any lights that are close enough
+			var totalWeight = 0f;
+			var accumulatedPosition = Vector3.zero;
+			for( var i = 0; i < _spriteLightPositions.Count; i++ )
+			{
+				var sqrDistance = sqrDistanceBetweenVectors( position, _spriteLightPositions[i] );
+				if( sqrDistance < maxSqrDistance )
+				{
+					// weight should be greater for closer lights and less for further away
+					var weight = maxSqrDistance - sqrDistance;
+
+					// tally the total weight
+					totalWeight += weight;
+					accumulatedPosition += ( weight * _spriteLightPositions[i] );
+				}
+			}
+
+			// if we have a totalWeight we need to take into account
+			if( totalWeight > 0 )
+			{
+				return accumulatedPosition * ( 1f / totalWeight );
+			}
+
+			return position;
+		}
+
+
+		public float sqrDistanceBetweenVectors( Vector3 a, Vector3 b )
+		{
+			return new Vector2( a.x - b.x, a.y - b.y ).sqrMagnitude;
+		}
+	}
+}

Assets/SpriteLightKit/Shadows/SpriteLightKitShadow.cs

@@ -0,0 +1,47 @@
+using UnityEngine;
+using System.Collections;
+
+
+namespace Prime31
+{
+	public class SpriteLightKitShadow : MonoBehaviour
+	{
+		[Tooltip( "Maximum distance that a light can be from the sprite to still affect it" )]
+		public float maxLightSqrDistance = 100f;
+		[Tooltip( "The maximum offset from the sprite that the shadow can be" )]
+		public float maxShadowTranslation = 0.5f;
+		[Tooltip( "The averaged light distance is multiplied by this and it affects how far the shadow will offset from the sprite" )]
+		public float shadowDistanceMultiplier = 1f;
+
+		SpriteLightKitLightManager _slkLightManager;
+		Transform _transform;
+		Material _material;
+
+
+		void Awake()
+		{
+			_slkLightManager = FindObjectOfType<SpriteLightKitLightManager>();
+			_transform = gameObject.transform;
+			_material = GetComponent<SpriteRenderer>().material;
+		}
+
+
+		void Update()
+		{
+			// we dont want the z component to influence anything
+			var position = _transform.position;
+			position.z = 0f;
+
+			var nearestLightPosition = _slkLightManager.getAffectedAverageLightPos( position, maxLightSqrDistance );
+
+			//Debug.DrawLine( position, nearestLightPosition, Color.red, 0.1f );
+
+			var lightDistance = _slkLightManager.sqrDistanceBetweenVectors( position, nearestLightPosition );
+			var lightDir = ( position - nearestLightPosition ).normalized * lightDistance * shadowDistanceMultiplier;
+			lightDir /= maxLightSqrDistance;
+
+			_material.SetFloat( "_HorizontalTranslation", Mathf.Clamp( lightDir.x, -maxShadowTranslation, maxShadowTranslation ) );
+			_material.SetFloat( "_VerticalTranslation", Mathf.Clamp( lightDir.y, -maxShadowTranslation, maxShadowTranslation ) );
+		}
+	}
+}