Grid.shader

// Upgrade NOTE: upgraded instancing buffer 'Props' to new syntax.

Shader "PDT Shaders/TestGrid" {
	Properties {
		_LineColor ("Line Color", Color) = (1,1,1,1)
		_InactiveColor ("Inactive Color", Color) = (0,1,0,1)
		_ActiveColor ("Active Color", Color) = (1,0,0,1)
		[PerRendererData] _MainTex ("Albedo (RGB)", 2D) = "white" {}
		[IntRange] _GridSize("Grid Size", Range(1,100)) = 10
		_LineSize("Line Size", Range(0,1)) = 0.15
	}
	SubShader {
		Tags { "Queue"="AlphaTest" "RenderType"="TransparentCutout" }
		LOD 200
	

		CGPROGRAM
        // Upgrade NOTE: excluded shader from DX11, OpenGL ES 2.0 because it uses unsized arrays
        #pragma exclude_renderers d3d11 gles
		// Physically based Standard lighting model, and enable shadows on all light types
		#pragma surface surf Standard fullforwardshadows

		// Use shader model 3.0 target, to get nicer looking lighting
		#pragma target 3.0

		sampler2D _MainTex;

		struct Input {
			float2 uv_MainTex;
		};

		half _Glossiness = 0.0;
		half _Metallic = 0.0;
		
		float4 _LineColor; // Line Color
		float _LineSize; // Width of Line
		
		// Color gradient endpoints
		float4 _InactiveColor; // Color of 0.0 value
		float4 _ActiveColor; // Color of 1.0 value
        
		float2 _GridSize; // Integer grid size
		float _Values[500]; // Flattened array containing all interpolation

		// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
		// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
		// #pragma instancing_options assumeuniformscaling
		UNITY_INSTANCING_BUFFER_START(Props)
			// put more per-instance properties here
		UNITY_INSTANCING_BUFFER_END(Props)

		void surf (Input IN, inout SurfaceOutputStandard o) {
			// Albedo comes from a texture tinted by color

			float2 uv = IN.uv_MainTex;
			fixed4 c = float4(0.0,0.0,0.0,0.0);
			float brightness = 1.0;
			
			// _GridSize = floor(_GridSize);
			float gsize = floor(_GridSize) + _LineSize;
            
            // Get grid position
			float2 id = float2(floor(uv.x / (1.0 / gsize)), floor(uv.y / (1.0 / gsize)));

			float4 color = _InactiveColor;
			brightness = _InactiveColor.w;
            
            
			 if (frac(uv.x * gsize) <= _LineSize || frac(uv.y * gsize) <= _LineSize)
			 {
				brightness = _LineColor.w;
			 	color = _LineColor;
			} else {
			     float value = _Values[_GridSize.x * uv.y + uv.x];
			    // float value = 0.5;
				 color = lerp(_InactiveColor, _ActiveColor, value);
				brightness = color.w;
			}
			

			//Clip transparent spots using alpha cutout
			if (brightness == 0.0) {
				clip(c.a - 1.0);
			}

			o.Albedo = float4(color.x * brightness, color.y * brightness, color.z * brightness, brightness);
			// Metallic and smoothness come from slider variables
			o.Metallic = 0.0;
			o.Smoothness = 0.0;
			o.Alpha = 0.0;
		}
		ENDCG
	}
	FallBack "Diffuse"
}

GridController.cs

using UnityEngine;

/// <summary>
/// A simple Grid Rendering Controller using MeshRenderer.
/// </summary>
public class GridController : MonoBehaviour {
    public int width = 32;
    public int height = 32;

    public Material gridMaterial;
    private float[] values;
    
    private void Start() {
        values = new float[width * height];
        for (int x = 0; x < width; x++) {
            for (int y = 0; y < height; y++) {
                SetValue(x, y, Random.value);
            }
        }
        gridMaterial.SetVector("_GridSize", new Vector4(width, height, 0, 0));
    }
    
    private void Update() {
        gridMaterial.SetFloatArray("_Values", values);
    }

    public void SetValue(int x, int y, float value) {
        values[width * y + x] = value;
    }

    public float GetValue(int x, int y) {
        return values[width * y + x];
    }
}