Grid2.shader

Shader "Custom/GridShader" {
	Properties{
		_BgColor("Background Color", Color) = (.5, .5, .5, 1)
		_MaskColor("Mask Color", Color) = (0, 0, 0, 1)

		/*
		Two circles over each others for better contrast
		Masks
			Have quads fill camera frustum
			Set mask position with shader
		*/
		_nRows("Number of rows", int) = 0
		_nCols("Number of columns", int) = 0

		_Radius("Radius", Range(0,.5)) = .25

		_QuadRatio("Y/X quad ratio (FoV ratio)", float) = .1

		// Ring 0 is located at the bottom left
		_TargetCircle("Target ring", int) = 0
	}

		SubShader{

		Tags { "Queue" = "Transparent" }
		Pass{

		// No culling or depth
		Cull Off ZWrite Off ZTest Always
		// Modify alpha on current texture showing what's behind
		blend SrcAlpha OneMinusSrcAlpha

		CGPROGRAM
		#pragma vertex vert
		#pragma fragment frag
		#pragma target 3.0

		#include "UnityCG.cginc"

		struct appdata
		{
			float2 uv : TEXCOORD0;
			float4 vertex : POSITION;
		};

		struct v2f
		{
			float2 uv : TEXCOORD0;
			float4 vertex : SV_POSITION;
		};

		v2f vert(appdata v)
		{
			v2f o;
			o.vertex = UnityObjectToClipPos(v.vertex);
			o.uv = v.uv;
			return o;
		}

		float4 _BgColor;
		float4 _MaskColor;

		half _Radius;

		uint _nRows;
		uint _nCols;
		half _sparsiness;

		float _QuadRatio;

		uint _TargetCircle;

		bool ring(float2 pos, float2 center, float radius) {
			// Get position relative to circle center position
			// Correct Y coords relative to the bigger width - Assume: width > height!!
			float2 relPos = float2(center.x, center.y - (_QuadRatio - 1) / 2) - float2(pos.x, pos.y / _QuadRatio);

			// Euclidean distance to circle center
			float dist = length(relPos);

			// Filled circle
			return !(dist > radius);
		}

		fixed4 frag(v2f i) : SV_Target{

			// Is this pixel part of the circles?
			bool rings = false;

			for (uint irow = 0; irow < _nRows; irow++) {
				for (uint icol = 0; icol < _nCols; icol++) {
					// Circl pos: 0 is bottom left, increments left to right 
					uint icirl = icol * _nRows + irow;
					float2 circle_pos = float2(
							float(irow) / _nRows + 1. / _nRows / 2, // X&Y pos
							float(icol) / _nCols + 1. / _nCols / 2  // add X&Yspacing 
						);
					// If target: (-1 means all)

					if (_TargetCircle == icirl) {
						// Concentric rings
						rings = rings | ring(i.uv.xy, circle_pos, _Radius*1.4);
						rings = rings & !ring(i.uv.xy, circle_pos, _Radius*1.2);
						rings = rings | ring(i.uv.xy, circle_pos, _Radius);
						rings = rings & !ring(i.uv.xy, circle_pos, _Radius*.8);
						rings = rings | ring(i.uv.xy, circle_pos, _Radius*.6);
						rings = rings & !ring(i.uv.xy, circle_pos, _Radius*.4);
						rings = rings | ring(i.uv.xy, circle_pos, _Radius*.2);
					}
else if (true) {
 rings = rings | ring(i.uv.xy, circle_pos, _Radius);
 rings = rings & !ring(i.uv.xy, circle_pos, _Radius*.65);
}
}
}

return rings * _MaskColor + (1 - rings) * _BgColor;
}
ENDCG
}
	}
}