implement height based terrain lighting for water

Author: Andreas-W

Core/GameEngineDevice/Source/W3DDevice/GameClient/BaseHeightMap.cpp

@@ -1,4 +1,4 @@
-/*
+/*
 **	Command & Conquer Generals Zero Hour(tm)
 **	Copyright 2025 Electronic Arts Inc.
 **
@@ -492,6 +492,13 @@ void BaseHeightMapRenderObjClass::ReAcquireResources(void)
 	}
 }
 
+// --------
+static float invLerp(float a, float b, float v)
+{
+	if (a == b) return 0.0f; // avoid divide by zero
+	return (v - a) / (b - a);
+}
+
 //=============================================================================
 // BaseHeightMapRenderObjClass::doTheLight
 //=============================================================================
@@ -591,6 +598,99 @@ void BaseHeightMapRenderObjClass::doTheLight(VERTEX_FORMAT *vb, Vector3*light, V
 	if (shadeB > 1.0) shadeB = 1.0;
 	if(shadeB < 0.0f) shadeB = 0.0f;
 
+	// ---------------------------------------------
+	// Height based ambient light factor (for water)
+	// ---------------------------------------------
+	if (TheGlobalData &&
+		TheGlobalData->m_terrainHeightAmbientLightHeightStart > 0 &&
+		(TheGlobalData->m_terrainHeightAmbientLightHeight1 >= 0 || TheGlobalData->m_terrainHeightAmbientLightHeight2 >= 0) &&
+		vb->z <= TheGlobalData->m_terrainHeightAmbientLightHeightStart
+		) {
+		Real col1R, col1G, col1B, col2R, col2G, col2B;
+		//Real factor1 = 0.0;
+		//Real factor2 = 0.0;
+		Real height1 = -1;
+		Real height2 = -1;
+
+		Real colR;
+		Real colG;
+		Real colB;
+
+		// case 1: only one color
+		if (TheGlobalData->m_terrainHeightAmbientLightHeight1 <= 0)
+		{
+			col1R = TheGlobalData->m_terrainHeightAmbientLightColor2.red;
+			col1G = TheGlobalData->m_terrainHeightAmbientLightColor2.green;
+			col1B = TheGlobalData->m_terrainHeightAmbientLightColor2.blue;
+			height1 = TheGlobalData->m_terrainHeightAmbientLightHeight2;
+		}
+		else if (TheGlobalData->m_terrainHeightAmbientLightHeight2 <= 0) {
+			col1R = TheGlobalData->m_terrainHeightAmbientLightColor1.red;
+			col1G = TheGlobalData->m_terrainHeightAmbientLightColor1.green;
+			col1B = TheGlobalData->m_terrainHeightAmbientLightColor1.blue;
+			height1 = TheGlobalData->m_terrainHeightAmbientLightHeight1;
+		}
+		else
+		{ // case 2: both colors
+
+			col1R = TheGlobalData->m_terrainHeightAmbientLightColor1.red;
+			col1G = TheGlobalData->m_terrainHeightAmbientLightColor1.green;
+			col1B = TheGlobalData->m_terrainHeightAmbientLightColor1.blue;
+			col2R = TheGlobalData->m_terrainHeightAmbientLightColor2.red;
+			col2G = TheGlobalData->m_terrainHeightAmbientLightColor2.green;
+			col2B = TheGlobalData->m_terrainHeightAmbientLightColor2.blue;
+			height1 = TheGlobalData->m_terrainHeightAmbientLightHeight1;
+			height2 = TheGlobalData->m_terrainHeightAmbientLightHeight2;
+		}
+
+		bool multiply = !TheGlobalData->m_terrainHeightAmbientLightAdditive;
+		Real base;
+		if (multiply)
+			base = 1.0;
+		else
+			base = 0.0;
+
+		if (vb->z > height1) {
+			Real t = WWMath::Clamp(invLerp(TheGlobalData->m_terrainHeightAmbientLightHeightStart, height1, vb->z));
+			colR = col1R * t + (1.0 - t) * base;
+			colG = col1G * t + (1.0 - t) * base;
+			colB = col1B * t + (1.0 - t) * base;
+		}
+
+		// Between height1 and height2
+		else if (height2 > -1 && vb->z > height2)
+		{
+			Real t = WWMath::Clamp(invLerp(height1, height2, vb->z));
+			Real factor1 = 1.0f - t; // 1 → 0
+			Real factor2 = t;        // 0 → 1
+
+			colR = col1R * factor1 + col2R * factor2;
+			colG = col1G * factor1 + col2G * factor2;
+			colB = col1B * factor1 + col2B * factor2;
+		}
+		// below
+		else {
+			colR = col2R;
+			colG = col2G;
+			colB = col2B;
+		}
+
+		if (multiply) {
+			shadeR *= colR;
+			shadeG *= colG;
+			shadeB *= colB;
+		}
+		else {
+			shadeR = WWMath::Clamp(shadeR + colR);
+			shadeG = WWMath::Clamp(shadeG + colG);
+			shadeB = WWMath::Clamp(shadeB + colB);
+		}
+	}
+	// ---------------------------------------------
+
+
+
+	// Old, inactive code
 	if (m_useDepthFade && vb->z <= TheGlobalData->m_waterPositionZ)
 	{	//height is below water level
 		//reduce lighting values based on light fall off as it travels through water.

GeneralsMD/Code/GameEngine/Include/Common/GlobalData.h

@@ -590,6 +590,14 @@ class GlobalData : public SubsystemInterface
 	Bool m_heightAboveTerrainIncludesWater;
 	Bool m_hideScorchmarksAboveGround;
 
+	// Water depth lighting
+	RGBColor m_terrainHeightAmbientLightColor1;
+	RGBColor m_terrainHeightAmbientLightColor2;
+	Real m_terrainHeightAmbientLightHeightStart;
+	Real m_terrainHeightAmbientLightHeight1;
+	Real m_terrainHeightAmbientLightHeight2;
+	Bool m_terrainHeightAmbientLightAdditive;
+
 	// the trailing '\' is included!
   const AsciiString &getPath_UserData() const { return m_userDataDir; }
 

GeneralsMD/Code/GameEngine/Source/Common/GlobalData.cpp

@@ -575,6 +575,14 @@ GlobalData* GlobalData::m_theOriginal = NULL;
 	{"DefaultExcludedDeathTypes", INI::parseDeathTypeFlagsList, NULL, offsetof(GlobalData, m_defaultExcludedDeathTypes) },
 	{"HeightAboveTerrainIncludesWater", INI::parseBool, NULL, offsetof(GlobalData, m_heightAboveTerrainIncludesWater) },
 	{"HideScorchmarksAboveGround", INI::parseBool, NULL, offsetof(GlobalData, m_hideScorchmarksAboveGround) },
+
+
+	{ "TerrainHeightAmbientLightColor1",			INI::parseRGBColor,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightColor1) },
+	{ "TerrainHeightAmbientLightColor2",			INI::parseRGBColor,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightColor2) },
+	{ "TerrainHeightAmbientLightStart",			INI::parseReal,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightHeightStart) },
+	{ "TerrainHeightAmbientLightHeight1",			INI::parseReal,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightHeight1) },
+	{ "TerrainHeightAmbientLightHeight2",			INI::parseReal,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightHeight2) },
+	{ "TerrainHeightAmbientLightAdditive",			INI::parseBool,			NULL,			offsetof(GlobalData, m_terrainHeightAmbientLightAdditive) },
 	{ NULL,					NULL,						NULL,						0 }  // keep this last
 
 };
@@ -1163,6 +1171,20 @@ GlobalData::GlobalData()
 
 	m_heightAboveTerrainIncludesWater = false;
 
+	m_terrainHeightAmbientLightColor1.red = 0;
+	m_terrainHeightAmbientLightColor1.green = 0;
+	m_terrainHeightAmbientLightColor1.blue = 0;
+
+	m_terrainHeightAmbientLightColor2.red = 0;
+	m_terrainHeightAmbientLightColor2.green = 0;
+	m_terrainHeightAmbientLightColor2.blue = 0;
+
+	m_terrainHeightAmbientLightHeightStart = -1;
+	m_terrainHeightAmbientLightHeight1 = -1;
+	m_terrainHeightAmbientLightHeight2 = -1;
+
+	m_terrainHeightAmbientLightAdditive = false;
+
 }  // end GlobalData