From bad19d99548e9099728f8272bae9f10decf516ca Mon Sep 17 00:00:00 2001
From: BlackYps <52536103+BlackYps@users.noreply.github.com>
Date: Thu, 9 Nov 2023 19:37:20 +0100
Subject: [PATCH] Water improvements (#5654)

---
 effects/mesh.fx    | 18 ++++++++++--------
 effects/terrain.fx | 10 +++++-----
 effects/water2.fx  | 14 ++++++--------
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/effects/mesh.fx b/effects/mesh.fx
index be7062a0be..ffac15548d 100644
--- a/effects/mesh.fx
+++ b/effects/mesh.fx
@@ -601,24 +601,26 @@ float3 ComputeNormal( sampler2D source, float2 uv, float3x3 rotationMatrix)
 float3 ApplyWaterColor(float depth, float3 viewDirection, float3 color, float3 emission = float3(0, 0, 0)) {
     // disable the whole thing on land-only maps
     if (surfaceElevation > 0) {
-        float4 waterColor = tex1D(WaterRampSampler, -depth / (surfaceElevation - abyssElevation));
         // we need this switch to make it consistent with the terrain shader coloration
         if (IsExperimentalShader()) {
+            float scaledDepth = (-depth / (surfaceElevation - abyssElevation));
             float3 up = float3(0,1,0);
-            // To simplify, we assume that the light enters vertically into the water,
             // this is the length that the light travels underwater back to the camera
             float oneOverCosV = 1 / max(dot(up, normalize(viewDirection)), 0.0001);
-            // light gets absorbed exponentially
-            float waterAbsorption = saturate(exp(-waterColor.w * (1 + oneOverCosV)));
+            // Light gets absorbed exponentially.
+            // To simplify, we assume that the light enters vertically into the water.
+            float waterAbsorption = 1 - saturate(exp(-scaledDepth * (1 + oneOverCosV)));
             // when the mesh emits light, then the path from the surface to the mesh doesn't apply
-            float emissionAbsorption = saturate(exp(-waterColor.w * oneOverCosV));
+            float emissionTransmitted = saturate(exp(-scaledDepth * oneOverCosV));
             // darken the color first to simulate the light absorption on the way in and out
-            color *= waterAbsorption;
+            color *= 1 - waterAbsorption;
             // lerp in the watercolor to simulate the scattered light from the dirty water
-            color = lerp(waterColor.rgb, color, waterAbsorption);
+            float4 waterColor = tex1D(WaterRampSampler, waterAbsorption);
+            color = lerp(color, waterColor.rgb, waterAbsorption);
             // similarly tune down the emission light
-            color += emission * emissionAbsorption;
+            color += emission * emissionTransmitted;
         } else {
+            float4 waterColor = tex1D(WaterRampSampler, -depth / (surfaceElevation - abyssElevation));
             color = lerp(color, waterColor.rgb, waterColor.w);
             color += emission;
         }
diff --git a/effects/terrain.fx b/effects/terrain.fx
index bd519bb755..1ac27e5feb 100644
--- a/effects/terrain.fx
+++ b/effects/terrain.fx
@@ -405,16 +405,16 @@ float3 ApplyWaterColorExponentially(float3 viewDirection, float terrainHeight, f
 {
     if (waterDepth > 0) {
         float opacity = saturate(smoothstep(10, 200, CameraPosition.y - WaterElevation) + step(terrainHeight, WaterElevation));
-        float4 waterColor = tex1D(WaterRampSampler, waterDepth);
         float3 up = float3(0,1,0);
-        // To simplify, we assume that the light enters vertically into the water,
         // this is the length that the light travels underwater back to the camera
-        float oneOverCosV = 1 / max(abs(dot(up, normalize(viewDirection))), 0.0001);
-        // light gets absorbed exponentially
-        float waterAbsorption = 1 - saturate(exp(-waterColor.w * (1 + oneOverCosV)));
+        float oneOverCosV = 1 / max(dot(up, normalize(viewDirection)), 0.0001);
+        // Light gets absorbed exponentially,
+        // to simplify, we assume that the light enters vertically into the water.
+        float waterAbsorption = 1 - saturate(exp(-waterDepth * (1 + oneOverCosV)));
         // darken the color first to simulate the light absorption on the way in and out
         color *= 1 - waterAbsorption * opacity;
         // lerp in the watercolor to simulate the scattered light from the dirty water
+        float4 waterColor = tex1D(WaterRampSampler, waterAbsorption);
         color = lerp(color, waterColor.rgb, waterAbsorption * opacity);
     }
     return color;
diff --git a/effects/water2.fx b/effects/water2.fx
index 7a6eef8d1f..a18e413297 100644
--- a/effects/water2.fx
+++ b/effects/water2.fx
@@ -24,9 +24,9 @@ float3 waveCrestColor = float3( 1, 1, 1);
 float4x4		WorldToView;
 float4x4		Projection;
 
-// red: wave normal strength
-// green: water depth
-// blue: ???
+// red: originally wave normal strength, now used for shadow
+// green: water depth (autogenerated by the engine)
+// blue: shoreline (autogenerated by the engine)
 // alpha: foam reduction
 texture		UtilityTextureC;
 
@@ -350,10 +350,6 @@ float4 HighFidelityPS( VS_OUTPUT inV,
     // scale, bias and normalize
     float3 N = 2.0 * sum.xyz - 4.0;
     N = normalize(N.xzy); 
-
-	// flatness
-    float3 up = float3(0,1,0);
-    N = lerp(up, N, waterTexture.r);
         
 	float3 R = reflect(-viewVector, N);
 
@@ -396,10 +392,12 @@ float4 HighFidelityPS( VS_OUTPUT inV,
     sunReflection = sunReflection * fresnel;
 	// the sun shouldn't be visible where a unit reflection is
 	sunReflection *= (1 - saturate(reflectedPixels.a * 2));
+	// we can control this value to have terrain cast a shadow on the water surface
+	sunReflection *= waterTexture.r;
     refractedPixels.xyz +=  sunReflection;
 
     // Lerp in the wave crests
-    refractedPixels.xyz = lerp(refractedPixels.xyz, waveCrestColor, (1 - waterTexture.a) * waveCrest);
+    refractedPixels.xyz = lerp(refractedPixels.xyz, waveCrestColor, (1 - waterTexture.a) * (1 - waterTexture.b) * waveCrest);
 
     // return the pixels masked out by the water mask
     float4 returnPixels = refractedPixels;