diff --git a/source/renderer/DebugRenderer.cpp b/source/renderer/DebugRenderer.cpp
index c559091876..eedd085230 100644
--- a/source/renderer/DebugRenderer.cpp
+++ b/source/renderer/DebugRenderer.cpp
@@ -137,7 +137,7 @@ void CDebugRenderer::DrawCircle(const CVector3D& origin, const float radius, con
 #endif
 }
 
-void CDebugRenderer::DrawCameraFrustum(const CCamera& camera, int intermediates) const
+void CDebugRenderer::DrawCameraFrustum(const CCamera& camera, const CColor& color, int intermediates) const
 {
 #if CONFIG2_GLES
 #warning TODO: implement camera frustum for GLES
@@ -153,52 +153,73 @@ void CDebugRenderer::DrawCameraFrustum(const CCamera& camera, int intermediates)
 		farPoints[i] = camera.m_Orientation.Transform(farPoints[i]);
 	}
 
-	// near plane
-	glBegin(GL_POLYGON);
-		glVertex3fv(&nearPoints[0].X);
-		glVertex3fv(&nearPoints[1].X);
-		glVertex3fv(&nearPoints[2].X);
-		glVertex3fv(&nearPoints[3].X);
-	glEnd();
+	CShaderTechniquePtr overlayTech =
+		g_Renderer.GetShaderManager().LoadEffect(str_debug_line);
+	overlayTech->BeginPass();
+	CShaderProgramPtr overlayShader = overlayTech->GetShader();
 
-	// far plane
-	glBegin(GL_POLYGON);
-		glVertex3fv(&farPoints[0].X);
-		glVertex3fv(&farPoints[1].X);
-		glVertex3fv(&farPoints[2].X);
-		glVertex3fv(&farPoints[3].X);
-	glEnd();
+	overlayShader->Bind();
+	overlayShader->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());
+	overlayShader->Uniform(str_color, color);
 
-	// connection lines
-	glBegin(GL_QUAD_STRIP);
-		glVertex3fv(&nearPoints[0].X);
-		glVertex3fv(&farPoints[0].X);
-		glVertex3fv(&nearPoints[1].X);
-		glVertex3fv(&farPoints[1].X);
-		glVertex3fv(&nearPoints[2].X);
-		glVertex3fv(&farPoints[2].X);
-		glVertex3fv(&nearPoints[3].X);
-		glVertex3fv(&farPoints[3].X);
-		glVertex3fv(&nearPoints[0].X);
-		glVertex3fv(&farPoints[0].X);
-	glEnd();
+	std::vector<float> vertices;
+#define ADD(position) \
+	vertices.emplace_back((position).X); \
+	vertices.emplace_back((position).Y); \
+	vertices.emplace_back((position).Z);
 
-	// intermediate planes
+	// Near plane.
+	ADD(nearPoints[0]);
+	ADD(nearPoints[1]);
+	ADD(nearPoints[2]);
+	ADD(nearPoints[3]);
+
+	// Far plane.
+	ADD(farPoints[0]);
+	ADD(farPoints[1]);
+	ADD(farPoints[2]);
+	ADD(farPoints[3]);
+
+	// Intermediate planes.
 	CVector3D intermediatePoints[4];
 	for(int i = 0; i < intermediates; ++i)
 	{
-		float t = (i + 1.0f) / (intermediates + 1.0f);
+		const float t = (i + 1.0f) / (intermediates + 1.0f);
 
 		for(int j = 0; j < 4; ++j)
 			intermediatePoints[j] = nearPoints[j] * t + farPoints[j] * (1.0f - t);
 
-		glBegin(GL_POLYGON);
-			glVertex3fv(&intermediatePoints[0].X);
-			glVertex3fv(&intermediatePoints[1].X);
-			glVertex3fv(&intermediatePoints[2].X);
-			glVertex3fv(&intermediatePoints[3].X);
-		glEnd();
+		ADD(intermediatePoints[0]);
+		ADD(intermediatePoints[1]);
+		ADD(intermediatePoints[2]);
+		ADD(intermediatePoints[3]);
 	}
+
+	overlayShader->VertexPointer(3, GL_FLOAT, 0, vertices.data());
+	overlayShader->AssertPointersBound();
+	glDrawArrays(GL_QUADS, 0, vertices.size() / 3);
+
+	vertices.clear();
+
+	// Connection lines.
+	ADD(nearPoints[0]);
+	ADD(farPoints[0]);
+	ADD(nearPoints[1]);
+	ADD(farPoints[1]);
+	ADD(nearPoints[2]);
+	ADD(farPoints[2]);
+	ADD(nearPoints[3]);
+	ADD(farPoints[3]);
+	ADD(nearPoints[0]);
+	ADD(farPoints[0]);
+
+	overlayShader->VertexPointer(3, GL_FLOAT, 0, vertices.data());
+	overlayShader->AssertPointersBound();
+	glDrawArrays(GL_QUAD_STRIP, 0, vertices.size() / 3);
+#undef ADD
+
+	overlayShader->Unbind();
+	overlayTech->EndPass();
 #endif
 }
 
diff --git a/source/renderer/DebugRenderer.h b/source/renderer/DebugRenderer.h
index ed13db900b..80faf29346 100644
--- a/source/renderer/DebugRenderer.h
+++ b/source/renderer/DebugRenderer.h
@@ -52,7 +52,7 @@ public:
 	 * @param intermediates determines how many intermediate distance planes should
 	 * be hinted at between the near and far planes
 	 */
-	void DrawCameraFrustum(const CCamera& camera, int intermediates = 0) const;
+	void DrawCameraFrustum(const CCamera& camera, const CColor& color, int intermediates = 0) const;
 
 	/**
 	 * Render the surfaces of the bound box as triangles.
diff --git a/source/renderer/TerrainOverlay.cpp b/source/renderer/TerrainOverlay.cpp
index 1ccfd4ebf8..3434bc00ee 100644
--- a/source/renderer/TerrainOverlay.cpp
+++ b/source/renderer/TerrainOverlay.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2021 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -20,6 +20,8 @@
 #include "TerrainOverlay.h"
 
 #include "graphics/Color.h"
+#include "graphics/ShaderManager.h"
+#include "graphics/ShaderProgram.h"
 #include "graphics/Terrain.h"
 #include "lib/bits.h"
 #include "lib/ogl.h"
@@ -182,37 +184,56 @@ void TerrainOverlay::RenderTile(const CColor& color, bool draw_hidden, ssize_t i
 #warning TODO: implement TerrainOverlay::RenderTile for GLES
 #else
 
-	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
-
 	CVector3D pos[2][2];
 	for (int di = 0; di < 2; ++di)
 		for (int dj = 0; dj < 2; ++dj)
 			m_Terrain->CalcPosition(i + di, j + dj, pos[di][dj]);
 
-	glBegin(GL_TRIANGLES);
-		glColor4fv(color.FloatArray());
-		if (m_Terrain->GetTriangulationDir(i, j))
-		{
-			glVertex3fv(pos[0][0].GetFloatArray());
-			glVertex3fv(pos[1][0].GetFloatArray());
-			glVertex3fv(pos[0][1].GetFloatArray());
+	std::vector<float> vertices;
+#define ADD(position) \
+	vertices.emplace_back((position).X); \
+	vertices.emplace_back((position).Y); \
+	vertices.emplace_back((position).Z);
 
-			glVertex3fv(pos[1][0].GetFloatArray());
-			glVertex3fv(pos[1][1].GetFloatArray());
-			glVertex3fv(pos[0][1].GetFloatArray());
-		}
-		else
-		{
-			glVertex3fv(pos[0][0].GetFloatArray());
-			glVertex3fv(pos[1][0].GetFloatArray());
-			glVertex3fv(pos[1][1].GetFloatArray());
+	if (m_Terrain->GetTriangulationDir(i, j))
+	{
+		ADD(pos[0][0]);
+		ADD(pos[1][0]);
+		ADD(pos[0][1]);
 
-			glVertex3fv(pos[1][1].GetFloatArray());
-			glVertex3fv(pos[0][1].GetFloatArray());
-			glVertex3fv(pos[0][0].GetFloatArray());
-		}
-	glEnd();
+		ADD(pos[1][0]);
+		ADD(pos[1][1]);
+		ADD(pos[0][1]);
+	}
+	else
+	{
+		ADD(pos[0][0]);
+		ADD(pos[1][0]);
+		ADD(pos[1][1]);
 
+		ADD(pos[1][1]);
+		ADD(pos[0][1]);
+		ADD(pos[0][0]);
+	}
+#undef ADD
+
+	CShaderTechniquePtr overlayTech =
+		g_Renderer.GetShaderManager().LoadEffect(str_debug_line);
+	overlayTech->BeginPass();
+	CShaderProgramPtr overlayShader = overlayTech->GetShader();
+
+	overlayShader->Bind();
+	overlayShader->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());
+	overlayShader->Uniform(str_color, color);
+
+	overlayShader->VertexPointer(3, GL_FLOAT, 0, vertices.data());
+	overlayShader->AssertPointersBound();
+
+	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+	glDrawArrays(GL_TRIANGLES, 0, vertices.size() / 3);
+
+	overlayShader->Unbind();
+	overlayTech->EndPass();
 #endif
 }
 
@@ -243,18 +264,39 @@ void TerrainOverlay::RenderTileOutline(const CColor& color, int line_width, bool
 	if (line_width != 1)
 		glLineWidth((float)line_width);
 
-	CVector3D pos;
-	glBegin(GL_QUADS);
-		glColor4fv(color.FloatArray());
-		m_Terrain->CalcPosition(i,   j,   pos); glVertex3fv(pos.GetFloatArray());
-		m_Terrain->CalcPosition(i+1, j,   pos); glVertex3fv(pos.GetFloatArray());
-		m_Terrain->CalcPosition(i+1, j+1, pos); glVertex3fv(pos.GetFloatArray());
-		m_Terrain->CalcPosition(i,   j+1, pos); glVertex3fv(pos.GetFloatArray());
-	glEnd();
+	std::vector<float> vertices;
+#define ADD(i, j) \
+	m_Terrain->CalcPosition(i, j, position); \
+	vertices.emplace_back(position.X); \
+	vertices.emplace_back(position.Y); \
+	vertices.emplace_back(position.Z);
+
+	CVector3D position;
+	ADD(i,   j);
+	ADD(i+1, j);
+	ADD(i+1, j+1);
+	ADD(i,   j+1);
+#undef ADD
+
+	CShaderTechniquePtr overlayTech =
+		g_Renderer.GetShaderManager().LoadEffect(str_debug_line);
+	overlayTech->BeginPass();
+	CShaderProgramPtr overlayShader = overlayTech->GetShader();
+
+	overlayShader->Bind();
+	overlayShader->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());
+	overlayShader->Uniform(str_color, color);
+
+	overlayShader->VertexPointer(3, GL_FLOAT, 0, vertices.data());
+	overlayShader->AssertPointersBound();
+
+	glDrawArrays(GL_QUADS, 0, vertices.size() / 3);
+
+	overlayShader->Unbind();
+	overlayTech->EndPass();
 
 	if (line_width != 1)
 		glLineWidth(1.0f);
-
 #endif
 }