Index: ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.fp
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.fp
+++ ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.fp
@@ -0,0 +1,7 @@
+!!ARBfp1.0
+
+ATTRIB v_tex = fragment.texcoord[0];
+
+TEX result.color, v_tex, texture[0], 2D;
+
+END
Index: ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.vp
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.vp
+++ ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.vp
@@ -0,0 +1,19 @@
+!!ARBvp1.0
+
+PARAM transform[4] = { program.local[0..3] };
+PARAM textureTransform[4] = { program.local[4..7] };
+
+ATTRIB position = vertex.position;
+ATTRIB uv = vertex.texcoord[0];
+
+DP4 result.position.x, transform[0], position;
+DP4 result.position.y, transform[1], position;
+DP4 result.position.z, transform[2], position;
+DP4 result.position.w, transform[3], position;
+
+OUTPUT v_tex = result.texcoord[0];
+
+DP4 v_tex.x, textureTransform[0], uv;
+DP4 v_tex.y, textureTransform[1], uv;
+
+END
Index: ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.xml
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.xml
+++ ps/trunk/binaries/data/mods/public/shaders/arb/debug_overlay.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<program type="arb">
+
+    <vertex file="arb/debug_overlay.vp">
+        <uniform name="transform" loc="0" type="mat4"/>
+        <uniform name="textureTransform" loc="4" type="mat4"/>
+        <stream name="pos"/>
+        <stream name="uv0"/>
+    </vertex>
+
+    <fragment file="arb/debug_overlay.fp">
+        <uniform name="baseTex" loc="0" type="sampler2D"/>
+    </fragment>
+
+</program>
Index: ps/trunk/binaries/data/mods/public/shaders/effects/debug_overlay.xml
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/effects/debug_overlay.xml
+++ ps/trunk/binaries/data/mods/public/shaders/effects/debug_overlay.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<effect>
+
+    <technique>
+        <require shaders="arb"/>
+        <pass shader="arb/debug_overlay"/>
+    </technique>
+
+    <technique>
+        <require shaders="glsl"/>
+        <pass shader="glsl/debug_overlay"/>
+    </technique>
+
+</effect>
Index: ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.fs
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.fs
+++ ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.fs
@@ -0,0 +1,11 @@
+#version 110
+
+uniform sampler2D baseTex;
+
+varying vec2 v_tex;
+
+void main()
+{
+    vec4 base = texture2D(baseTex, v_tex);
+    gl_FragColor = base;
+}
Index: ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.vs
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.vs
+++ ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.vs
@@ -0,0 +1,15 @@
+#version 110
+
+uniform mat4 transform;
+uniform mat4 textureTransform;
+
+attribute vec3 a_vertex;
+attribute vec3 a_uv0;
+
+varying vec2 v_tex;
+
+void main()
+{
+	v_tex = (textureTransform * vec4(a_uv0, 1.0)).xy;
+	gl_Position = transform * vec4(a_vertex, 1.0);
+}
Index: ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.xml
===================================================================
--- ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.xml
+++ ps/trunk/binaries/data/mods/public/shaders/glsl/debug_overlay.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<program type="glsl">
+
+    <vertex file="glsl/debug_overlay.vs">
+        <stream name="pos"/>
+        <stream name="uv0"/>
+        <attrib name="a_vertex" semantics="gl_Vertex"/>
+        <attrib name="a_uv0" semantics="gl_MultiTexCoord0"/>
+    </vertex>
+
+    <fragment file="glsl/debug_overlay.fs"/>
+
+</program>
Index: ps/trunk/source/ps/CStrInternStatic.h
===================================================================
--- ps/trunk/source/ps/CStrInternStatic.h
+++ ps/trunk/source/ps/CStrInternStatic.h
@@ -87,6 +87,7 @@
 X(color)
 X(colorAdd)
 X(colorMul)
+X(debug_overlay)
 X(delta)
 X(depthTex)
 X(foamTex)
Index: ps/trunk/source/renderer/TerrainOverlay.cpp
===================================================================
--- ps/trunk/source/renderer/TerrainOverlay.cpp
+++ ps/trunk/source/renderer/TerrainOverlay.cpp
@@ -309,7 +309,7 @@
 	matrix._23 = m_TexelsPerTile / (m_TextureH * TERRAIN_TILE_SIZE);
 	matrix._44 = 1;
 
-	g_Renderer.GetTerrainRenderer().RenderTerrainOverlayTexture(cullGroup, matrix);
+	g_Renderer.GetTerrainRenderer().RenderTerrainOverlayTexture(cullGroup, matrix, m_Texture);
 }
 
 SColor4ub TerrainTextureOverlay::GetColor(size_t idx, u8 alpha) const
Index: ps/trunk/source/renderer/TerrainRenderer.h
===================================================================
--- ps/trunk/source/renderer/TerrainRenderer.h
+++ ps/trunk/source/renderer/TerrainRenderer.h
@@ -145,7 +145,7 @@
 	 * by the given texture matrix.
 	 * Intended for use by TerrainTextureOverlay.
 	 */
-	void RenderTerrainOverlayTexture(int cullGroup, CMatrix3D& textureMatrix);
+	void RenderTerrainOverlayTexture(int cullGroup, CMatrix3D& textureMatrix, GLuint texture);
 
 private:
 	TerrainRendererInternals* m;
Index: ps/trunk/source/renderer/TerrainRenderer.cpp
===================================================================
--- ps/trunk/source/renderer/TerrainRenderer.cpp
+++ ps/trunk/source/renderer/TerrainRenderer.cpp
@@ -397,72 +397,66 @@
 #endif
 }
 
-void TerrainRenderer::RenderTerrainOverlayTexture(int cullGroup, CMatrix3D& textureMatrix)
+void TerrainRenderer::RenderTerrainOverlayTexture(int cullGroup, CMatrix3D& textureMatrix, GLuint texture)
 {
 #if CONFIG2_GLES
 #warning TODO: implement TerrainRenderer::RenderTerrainOverlayTexture for GLES
 	UNUSED2(cullGroup);
 	UNUSED2(textureMatrix);
+	UNUSED2(texture);
 #else
 	ENSURE(m->phase == Phase_Render);
 
 	std::vector<CPatchRData*>& visiblePatches = m->visiblePatches[cullGroup];
 
-	glEnableClientState(GL_VERTEX_ARRAY);
-	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
-
-	pglActiveTextureARB(GL_TEXTURE0);
 	glEnable(GL_TEXTURE_2D);
 	glEnable(GL_BLEND);
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	glDepthMask(0);
 	glDisable(GL_DEPTH_TEST);
 
-	glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
-
-	glMatrixMode(GL_TEXTURE);
-	glLoadMatrixf(&textureMatrix._11);
-	glMatrixMode(GL_MODELVIEW);
+	CShaderTechniquePtr debugOverlayTech =
+		g_Renderer.GetShaderManager().LoadEffect(str_debug_overlay);
+	debugOverlayTech->BeginPass();
+	CShaderProgramPtr debugOverlayShader = debugOverlayTech->GetShader();
+
+	debugOverlayShader->Bind();
+	debugOverlayShader->BindTexture(str_baseTex, texture);
+	debugOverlayShader->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());
+	debugOverlayShader->Uniform(str_textureTransform, textureMatrix);
+	CPatchRData::RenderStreams(visiblePatches, debugOverlayShader, STREAM_POS | STREAM_POSTOUV0);
 
-	CShaderProgramPtr dummyShader = GetDummyShader();
-	dummyShader->Bind();
-	dummyShader->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());
-	dummyShader->Uniform(str_color, CColor(0.0f, 0.0f, 0.0f, 1.0f));
-	CPatchRData::RenderStreams(visiblePatches, dummyShader, STREAM_POS | STREAM_POSTOUV0);
-	dummyShader->Unbind();
+	glEnable(GL_DEPTH_TEST);
 
 	// To make the overlay visible over water, render an additional map-sized
-	// water-height patch
+	// water-height patch.
 	CBoundingBoxAligned waterBounds;
-	for (size_t i = 0; i < visiblePatches.size(); ++i)
-	{
-		CPatchRData* data = visiblePatches[i];
+	for (CPatchRData* data : visiblePatches)
 		waterBounds += data->GetWaterBounds();
-	}
 	if (!waterBounds.IsEmpty())
 	{
-		float h = g_Renderer.GetWaterManager()->m_WaterHeight + 0.05f; // add a delta to avoid z-fighting
-		float waterPos[] = {
-			waterBounds[0].X, h, waterBounds[0].Z,
-			waterBounds[1].X, h, waterBounds[0].Z,
-			waterBounds[0].X, h, waterBounds[1].Z,
-			waterBounds[1].X, h, waterBounds[1].Z
+		// Add a delta to avoid z-fighting.
+		const float height = g_Renderer.GetWaterManager()->m_WaterHeight + 0.05f;
+		const float waterPos[] = {
+			waterBounds[0].X, height, waterBounds[0].Z,
+			waterBounds[1].X, height, waterBounds[0].Z,
+			waterBounds[0].X, height, waterBounds[1].Z,
+			waterBounds[1].X, height, waterBounds[1].Z
 		};
-		glVertexPointer(3, GL_FLOAT, 3*sizeof(float), waterPos);
-		glTexCoordPointer(3, GL_FLOAT, 3*sizeof(float), waterPos);
+
+		const GLsizei stride = sizeof(float) * 3;
+		debugOverlayShader->VertexPointer(3, GL_FLOAT, stride, waterPos);
+		debugOverlayShader->TexCoordPointer(GL_TEXTURE0, 3, GL_FLOAT, stride, waterPos);
+		debugOverlayShader->AssertPointersBound();
+
 		glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 	}
 
-	glMatrixMode(GL_TEXTURE);
-	glLoadIdentity();
-	glMatrixMode(GL_MODELVIEW);
+	debugOverlayShader->Unbind();
+	debugOverlayTech->EndPass();
 
 	glDepthMask(1);
-	glEnable(GL_DEPTH_TEST);
 	glDisable(GL_BLEND);
-	glDisableClientState(GL_COLOR_ARRAY);
-	glDisableClientState(GL_VERTEX_ARRAY);
-	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 #endif
 }