Shader for rendering alpha stuck to ocean surface

src/unity/Assets/Crest-Examples/Materials/OceanAlpha_CrestLogo.mat

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src/unity/Assets/Crest-Examples/Scenes/main.unity

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src/unity/Assets/Crest-Examples/Scripts/RenderAlphaOnSurface.cs

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+using UnityEngine;
+using Crest;
+
+public class RenderAlphaOnSurface : MonoBehaviour
+{
+    Material _mat;
+
+	void Start()
+    {
+        _mat = GetComponent<Renderer>().material;
+    }
+
+    private void LateUpdate()
+    {
+        // find which lod this object is overlapping
+        var rect = new Rect(transform.position.x, transform.position.z, 0f, 0f);
+        var idx = WaveDataCam.SuggestCollisionLOD(rect);
+
+        if (idx > -1)
+        {
+            var pwm = new PropertyWrapperMaterial(_mat);
+            var wdcs = OceanRenderer.Instance.Builder._shapeWDCs;
+            wdcs[idx].ApplyMaterialParams(0, pwm);
+            int idx1 = Mathf.Min(idx + 1, wdcs.Length - 1);
+            wdcs[idx1].ApplyMaterialParams(1, pwm);
+
+            // blend LOD 0 shape in/out to avoid pop, if the ocean might scale up later (it is smaller than its maximum scale)
+            bool needToBlendOutShape = idx == 0 && OceanRenderer.Instance.ScaleCouldIncrease;
+            float meshScaleLerp = needToBlendOutShape ? OceanRenderer.Instance.ViewerAltitudeLevelAlpha : 0f;
+
+            // blend furthest normals scale in/out to avoid pop, if scale could reduce
+            bool needToBlendOutNormals = idx == wdcs.Length - 1 && OceanRenderer.Instance.ScaleCouldDecrease;
+            float farNormalsWeight = needToBlendOutNormals ? OceanRenderer.Instance.ViewerAltitudeLevelAlpha : 1f;
+            pwm.SetVector("_InstanceData", new Vector4(meshScaleLerp, farNormalsWeight, idx));
+        }
+    }
+}

src/unity/Assets/Crest-Examples/Shaders/OceanSurfaceAlpha.shader

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+Shader "Ocean/Ocean Surface Alpha"
+{
+	Properties
+	{
+		_MainTex ("Texture", 2D) = "white" {}
+		_Alpha("Alpha Multiplier", Range(0.0, 1.0)) = 1.0
+	}
+	SubShader
+	{
+		Tags { "RenderType"="Transparent" "Queue"="Transparent" }
+		LOD 100
+
+		Pass
+		{
+			Blend SrcAlpha OneMinusSrcAlpha
+			ZWrite Off
+			// Depth offset to stop intersection with water. "Factor" and "Units". typical seems to be (-1,-1). (-0.5,0) gives
+			// pretty good results for me when alpha geometry is fairly well matched but fails when alpha geo is too low res.
+			// the ludicrously large value below seems to work in most of my tests.
+			Offset 0, -1000000
+
+			CGPROGRAM
+			#pragma vertex vert
+			#pragma fragment frag
+			#pragma multi_compile_fog
+
+			#include "UnityCG.cginc"
+			#include "../../Crest/Shaders/OceanLODData.cginc"
+
+			struct appdata
+			{
+				float4 vertex : POSITION;
+				float2 uv : TEXCOORD0;
+			};
+
+			struct v2f
+			{
+				float2 uv : TEXCOORD0;
+				UNITY_FOG_COORDS(1)
+				float4 vertex : SV_POSITION;
+			};
+
+			sampler2D _MainTex;
+			float4 _MainTex_ST;
+			half _Alpha;
+
+			// MeshScaleLerp, FarNormalsWeight, LODIndex (debug), unused
+			uniform float4 _InstanceData;
+
+			v2f vert (appdata v)
+			{
+				v2f o;
+
+				// move to world
+				float3 worldPos = mul(unity_ObjectToWorld, v.vertex);
+
+				// vertex snapping and lod transition
+				float lodAlpha = ComputeLodAlpha_FromLODs(worldPos, _InstanceData.x);
+
+				// sample shape textures - always lerp between 2 scales, so sample two textures
+				half3 n = half3(0., 1., 0.);
+				half det = 0., signedOceanDepth = 0.;
+				// sample weights. params.z allows shape to be faded out (used on last lod to support pop-less scale transitions)
+				float wt_0 = (1. - lodAlpha) * _WD_Params_0.z;
+				float wt_1 = (1. - wt_0) * _WD_Params_1.z;
+				// sample displacement textures, add results to current world pos / normal / foam
+				const float2 wxz = worldPos.xz;
+				SampleDisplacements(_WD_Sampler_0, _WD_OceanDepth_Sampler_0, _WD_Pos_Scale_0.xy, _WD_Params_0.y, _WD_Params_0.w, _WD_Params_0.x, wxz, wt_0, worldPos, n, det, signedOceanDepth);
+				SampleDisplacements(_WD_Sampler_1, _WD_OceanDepth_Sampler_1, _WD_Pos_Scale_1.xy, _WD_Params_1.y, _WD_Params_1.w, _WD_Params_1.x, wxz, wt_1, worldPos, n, det, signedOceanDepth);
+
+				// view-projection	
+				o.vertex = mul(UNITY_MATRIX_VP, float4(worldPos, 1.));
+
+				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
+				UNITY_TRANSFER_FOG(o,o.vertex);
+				return o;
+			}
+
+			fixed4 frag (v2f i) : SV_Target
+			{
+				fixed4 col = tex2D(_MainTex, i.uv);
+
+				UNITY_APPLY_FOG(i.fogCoord, col);
+
+				col.a *= _Alpha;
+
+				return col;
+			}
+			ENDCG
+		}
+	}
+}