From 75bd640bd8742843b14ddbf39b1c45efd73e4796 Mon Sep 17 00:00:00 2001
From: Vladislav Belov <vladislavbelovdev@gmail.com>
Date: Sun, 10 May 2026 23:56:57 +0200
Subject: [PATCH] Removes context of terrain shadows and silhouettes

We were unnecessary passing all combinations of our scene shader context
even if we don't need it as for shadows and silhouettes for terrain
rendering. Since we only need to draw a solid color.
---
 .../shaders/effects/terrain_shadow_caster.xml | 11 ++++++++
 .../effects/terrain_silhouette_occluder.xml   | 16 ++++++++++++
 source/ps/CStrInternStatic.h                  |  2 ++
 source/renderer/SceneRenderer.cpp             |  4 +--
 source/renderer/TerrainRenderer.cpp           | 25 ++++++++++++++++++-
 5 files changed, 55 insertions(+), 3 deletions(-)
 create mode 100644 binaries/data/mods/mod/shaders/effects/terrain_shadow_caster.xml
 create mode 100644 binaries/data/mods/mod/shaders/effects/terrain_silhouette_occluder.xml

diff --git a/binaries/data/mods/mod/shaders/effects/terrain_shadow_caster.xml b/binaries/data/mods/mod/shaders/effects/terrain_shadow_caster.xml
new file mode 100644
index 0000000000..6f00b3d098
--- /dev/null
+++ b/binaries/data/mods/mod/shaders/effects/terrain_shadow_caster.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<effect>
+	<technique>
+		<require shaders="glsl"/>
+		<require shaders="spirv"/>
+		<pass shader="dummy">
+			<cull mode="FRONT"/>
+			<color mask_red="FALSE" mask_green="FALSE" mask_blue="FALSE" mask_alpha="FALSE"/>
+		</pass>
+	</technique>
+</effect>
diff --git a/binaries/data/mods/mod/shaders/effects/terrain_silhouette_occluder.xml b/binaries/data/mods/mod/shaders/effects/terrain_silhouette_occluder.xml
new file mode 100644
index 0000000000..0ea95bf7b9
--- /dev/null
+++ b/binaries/data/mods/mod/shaders/effects/terrain_silhouette_occluder.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<effect>
+	<technique>
+		<require shaders="glsl"/>
+		<require shaders="spirv"/>
+		<pass shader="dummy">
+			<!--
+				To prevent units displaying silhouettes when parts of their model
+				protrude into the ground, only occlude with the back faces of the
+				terrain (so silhouettes will still display when behind hills).
+			-->
+			<cull mode="FRONT"/>
+			<color mask_red="FALSE" mask_green="FALSE" mask_blue="FALSE" mask_alpha="FALSE"/>
+		</pass>
+	</technique>
+</effect>
diff --git a/source/ps/CStrInternStatic.h b/source/ps/CStrInternStatic.h
index 99d007f790..d9e8e5300e 100644
--- a/source/ps/CStrInternStatic.h
+++ b/source/ps/CStrInternStatic.h
@@ -171,6 +171,8 @@ X(sunDir)
 X(terrain_base)
 X(terrain_blend)
 X(terrain_decal)
+X(terrain_shadow_caster)
+X(terrain_silhouette_occluder)
 X(terrain_solid)
 X(tex)
 X(texSize)
diff --git a/source/renderer/SceneRenderer.cpp b/source/renderer/SceneRenderer.cpp
index 4d440e39f0..38e2f04394 100644
--- a/source/renderer/SceneRenderer.cpp
+++ b/source/renderer/SceneRenderer.cpp
@@ -317,7 +317,7 @@ void CSceneRenderer::RenderShadowMap(
 		const int cullGroup = CULL_SHADOWS_CASCADE_0 + cascade;
 		{
 			PROFILE("render patches");
-			m->terrainRenderer.RenderPatches(deviceCommandContext, cullGroup, shadowsContext);
+			m->terrainRenderer.RenderPatches(deviceCommandContext, cullGroup, {});
 		}
 
 		{
@@ -739,7 +739,7 @@ void CSceneRenderer::RenderSilhouettes(
 
 	{
 		PROFILE("render patches");
-		m->terrainRenderer.RenderPatches(deviceCommandContext, CULL_SILHOUETTE_OCCLUDER, contextOccluder);
+		m->terrainRenderer.RenderPatches(deviceCommandContext, CULL_SILHOUETTE_OCCLUDER, {});
 	}
 
 	{
diff --git a/source/renderer/TerrainRenderer.cpp b/source/renderer/TerrainRenderer.cpp
index 9b545fd131..da1c8cd4a9 100644
--- a/source/renderer/TerrainRenderer.cpp
+++ b/source/renderer/TerrainRenderer.cpp
@@ -93,6 +93,8 @@ struct TerrainRendererInternals
 	/// Fancy water shader
 	CShaderTechniquePtr fancyWaterTech;
 
+	CShaderTechniquePtr shadowCasterTech, silhouettteOccluderTech;
+
 	CShaderTechniquePtr shaderTechniqueSolid, shaderTechniqueSolidDepthTest;
 
 	Renderer::Backend::IVertexInputLayout* overlayVertexInputLayout = nullptr;
@@ -150,6 +152,10 @@ void TerrainRenderer::Initialize()
 	m->waterSurfaceVertexInputLayout = CPatchRData::GetWaterSurfaceVertexInputLayout(false);
 	m->waterSurfaceWithDataVertexInputLayout = CPatchRData::GetWaterSurfaceVertexInputLayout(true);
 	m->waterShoreVertexInputLayout = CPatchRData::GetWaterShoreVertexInputLayout();
+
+	CShaderManager& shaderManager{g_Renderer.GetShaderManager()};
+	m->shadowCasterTech = shaderManager.LoadEffect(str_terrain_shadow_caster);
+	m->silhouettteOccluderTech = shaderManager.LoadEffect(str_terrain_silhouette_occluder);
 }
 
 void TerrainRenderer::SetSimulation(CSimulation2* simulation)
@@ -372,7 +378,24 @@ void TerrainRenderer::RenderPatches(
 
 	GPU_SCOPED_LABEL(deviceCommandContext, "Render terrain patches");
 
-	CShaderTechniquePtr solidTech = g_Renderer.GetShaderManager().LoadEffect(str_terrain_solid, defines);
+	CShaderTechniquePtr solidTech;
+	switch (cullGroup)
+	{
+	case CSceneRenderer::CULL_SHADOWS_CASCADE_0: [[fallthrough]];
+	case CSceneRenderer::CULL_SHADOWS_CASCADE_1: [[fallthrough]];
+	case CSceneRenderer::CULL_SHADOWS_CASCADE_2: [[fallthrough]];
+	case CSceneRenderer::CULL_SHADOWS_CASCADE_3:
+		ENSURE(defines.GetMap().empty());
+		solidTech = m->shadowCasterTech;
+		break;
+	case CSceneRenderer::CULL_SILHOUETTE_OCCLUDER:
+		ENSURE(defines.GetMap().empty());
+		solidTech = m->silhouettteOccluderTech;
+		break;
+	default:
+		solidTech = g_Renderer.GetShaderManager().LoadEffect(str_terrain_solid, defines);
+		break;
+	}
 	deviceCommandContext->SetGraphicsPipelineState(
 		solidTech->GetGraphicsPipelineState());
 	deviceCommandContext->BeginPass();