From a19d7c92b51fa0272e1387d916a7fa4cfad61a26 Mon Sep 17 00:00:00 2001
From: andreykproductengine <andreykproductengine@lindenlab.com>
Date: Tue, 5 Feb 2019 22:14:35 +0200
Subject: temp fog

---
 indra/newview/lldrawpoolwater.cpp | 71 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 68 insertions(+), 3 deletions(-)

diff --git a/indra/newview/lldrawpoolwater.cpp b/indra/newview/lldrawpoolwater.cpp
index 23749d7adb..66d8306f97 100644
--- a/indra/newview/lldrawpoolwater.cpp
+++ b/indra/newview/lldrawpoolwater.cpp
@@ -59,6 +59,65 @@ BOOL LLDrawPoolWater::sNeedsReflectionUpdate = TRUE;
 BOOL LLDrawPoolWater::sNeedsDistortionUpdate = TRUE;
 F32 LLDrawPoolWater::sWaterFogEnd = 0.f;
 
+
+class LLFastLn
+{
+public:
+    LLFastLn()
+    {
+        mTable[0] = 0;
+        for (S32 i = 1; i < 257; i++)
+        {
+            mTable[i] = log((F32)i);
+        }
+    }
+
+    F32 ln(F32 x)
+    {
+        const F32 OO_255 = 0.003921568627450980392156862745098f;
+        const F32 LN_255 = 5.5412635451584261462455391880218f;
+
+        if (x < OO_255)
+        {
+            return log(x);
+        }
+        else
+            if (x < 1)
+            {
+                x *= 255.f;
+                S32 index = llfloor(x);
+                F32 t = x - index;
+                F32 low = mTable[index];
+                F32 high = mTable[index + 1];
+                return low + t * (high - low) - LN_255;
+            }
+            else
+                if (x <= 255)
+                {
+                    S32 index = llfloor(x);
+                    F32 t = x - index;
+                    F32 low = mTable[index];
+                    F32 high = mTable[index + 1];
+                    return low + t * (high - low);
+                }
+                else
+                {
+                    return log(x);
+                }
+    }
+
+    F32 pow(F32 x, F32 y)
+    {
+        return (F32)LL_FAST_EXP(y * ln(x));
+    }
+
+
+private:
+    F32 mTable[257]; // index 0 is unused
+};
+
+static LLFastLn gFastLn;
+
 LLDrawPoolWater::LLDrawPoolWater() : LLFacePool(POOL_WATER)
 {
 }
@@ -536,17 +595,23 @@ void LLDrawPoolWater::shade2(bool edge, LLGLSLShader* shader, const LLColor3& li
 
     shader->uniform1f(LLShaderMgr::BLEND_FACTOR, blend_factor);
 
+    F32 density = pwater->getWaterFogDensity();
+    F32 density_2 = gFastLn.pow(2.f, density);
     shader->uniform3fv(LLShaderMgr::WATER_FOGCOLOR, 1, pwater->getWaterFogColor().mV);
-    shader->uniform1f(LLShaderMgr::WATER_FOGDENSITY, pwater->getWaterFogDensity());
+    shader->uniform1f(LLShaderMgr::WATER_FOGDENSITY, density_2);
 	
     // bind reflection texture from RenderTarget
 	S32 screentex = shader->enableTexture(LLShaderMgr::WATER_SCREENTEX);
 	gGL.getTexUnit(screentex)->bind(&gPipeline.mWaterDis);	
 
 	if (mShaderLevel == 1)
-	{
+    {
+        density = llclamp(density, 0.f, 10.f);
+        density /= 10.0f;
+        density = 1.0f - density;
+        density *= density * density;
         LLColor4 fog_color(pwater->getWaterFogColor(), 0.f);
-        fog_color[3] = pwater->getWaterFogDensity();
+        fog_color[3] = density;
         shader->uniform4fv(LLShaderMgr::WATER_FOGCOLOR, 1, fog_color.mV);
 	}
 
-- 
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