diff --git a/data/shaders/fs_depthbuffer.glsl b/data/shaders/fs_depthbuffer.glsl
new file mode 100644
index 0000000..01e2638
--- /dev/null
+++ b/data/shaders/fs_depthbuffer.glsl
@@ -0,0 +1,17 @@
+#version 330 core
+
+in vec2 uv;
+
+out vec3 color;
+
+uniform sampler2D rendered_texture;
+uniform float near;
+uniform float far;
+
+void main() {
+	float z = texture(rendered_texture, uv).r;
+	float c = (2.0 * near) / (far + near - z * (far - near));
+	c = 2.0 * near * far / (far + near - z * (far - near));
+
+	color = vec3(z);
+}
diff --git a/data/shaders/fs_simpletexture.glsl b/data/shaders/fs_simpletexture.glsl
index 857e0cd..83c035b 100644
--- a/data/shaders/fs_simpletexture.glsl
+++ b/data/shaders/fs_simpletexture.glsl
@@ -14,6 +14,4 @@ void main() {
 		cos(time + 768.0  * uv.y)
 		)
 	).xyz;
-	color = vec3((texture(rendered_texture, uv).x + 1) * 0.5 );
-//	* 1 * (cos(time * 0.3) * 0.5) + 0.5);
 }
diff --git a/src/FileModificationObserver.h b/src/FileModificationObserver.h
new file mode 100644
index 0000000..4e3ad53
--- /dev/null
+++ b/src/FileModificationObserver.h
@@ -0,0 +1,85 @@
+#pragma once
+
+#include<unordered_map>
+#include<vector>
+
+struct AFileModificationListener {
+	virtual bool OnTrigger() = 0;
+};
+
+struct FileModificationObserver {
+	struct FileObserverInfo {
+		ino_t mFileId = 0;
+		int mFileMTime = 0;
+		int mFileMTimeNSec = 0;
+		off_t mFileSize = 0;
+		std::vector<AFileModificationListener*> mListeners;
+	};
+
+	typedef std::unordered_map<std::string, FileObserverInfo > FilenameListenerMap;
+	FilenameListenerMap mObserverInfos;
+
+	void AddListener(const std::string &filename, AFileModificationListener* listener) {
+		FilenameListenerMap::iterator iter;
+		iter = mObserverInfos.find(filename);
+
+		if (iter == mObserverInfos.end()) {
+			FileObserverInfo observer_info;
+			observer_info.mListeners.push_back(listener);
+			mObserverInfos[filename] = observer_info;
+		} else {
+			iter->second.mListeners.push_back(listener);
+		}
+	}
+
+	void Trigger(const std::string &filename) {
+		FilenameListenerMap::iterator iter;
+		iter = mObserverInfos.find(filename);
+
+		assert (iter != mObserverInfos.end());
+
+		std::vector<AFileModificationListener*>::iterator listener_iter = iter->second.mListeners.begin();
+		while (listener_iter != iter->second.mListeners.end()) {
+			if ((*listener_iter)->OnTrigger())
+				break;
+
+			listener_iter++;
+		}
+	}
+
+	void CheckFileModification(const std::string& filename, FileObserverInfo& observer_info) {
+		struct stat attr;
+		bool stat_result = stat(filename.c_str(), &attr);
+
+		if (stat_result != 0) {
+			gLog ("Error: could not stat watched file %s", filename.c_str());
+			abort();
+		}
+
+		if (   observer_info.mFileId != attr.st_ino 
+				|| observer_info.mFileMTime != attr.st_mtime
+				|| observer_info.mFileMTimeNSec != attr.st_mtim.tv_nsec
+				|| observer_info.mFileSize != attr.st_size
+				|| observer_info.mFileSize == 0 
+			 ) {
+			observer_info.mFileId = attr.st_ino;
+			observer_info.mFileMTime = attr.st_mtime;
+			observer_info.mFileMTimeNSec = attr.st_mtim.tv_nsec;
+			observer_info.mFileSize = attr.st_size;
+
+			gLog ("Detected file change of %s: new size %d",
+					filename.c_str(), attr.st_size);
+
+			Trigger(filename);
+		}
+	}
+
+	void Update() {
+		FilenameListenerMap::iterator iter = mObserverInfos.begin();
+
+		while (iter != mObserverInfos.end()) {
+			CheckFileModification(iter->first, iter->second);
+			iter++;
+		}
+	}
+};
diff --git a/src/modules/RenderModule.cc b/src/modules/RenderModule.cc
index aeed2df..79a9a38 100644
--- a/src/modules/RenderModule.cc
+++ b/src/modules/RenderModule.cc
@@ -144,12 +144,20 @@ glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data
 	glGenBuffers(1, &mRenderQuadVertexBufferId);
 	glBindBuffer(GL_ARRAY_BUFFER, mRenderQuadVertexBufferId);
 	glBufferData(GL_ARRAY_BUFFER, sizeof(g_quad_vertex_buffer_data), g_quad_vertex_buffer_data, GL_STATIC_DRAW);
+
+	// Program for color texture rendering
 	mRenderQuadProgramColor = RenderProgram("data/shaders/vs_passthrough.glsl", "data/shaders/fs_simpletexture.glsl");
 	load_result = mRenderQuadProgramColor.Load();
 	assert(load_result);
-
 	muRenderQuadTexture = glGetUniformLocation(mRenderQuadProgramColor.mProgramId, "rendered_texture");	
 	muRenderQuadTime = glGetUniformLocation(mRenderQuadProgramColor.mProgramId, "time");	
+
+	// Program for depth texture rendering
+	mRenderQuadProgramDepth = RenderProgram("data/shaders/vs_passthrough.glsl", "data/shaders/fs_depthbuffer.glsl");
+	load_result = mRenderQuadProgramDepth.Load();
+	assert(load_result);
+	muRenderQuadDepthNear = glGetUniformLocation(mRenderQuadProgramDepth.mProgramId, "near");	
+	muRenderQuadDepthFar = glGetUniformLocation(mRenderQuadProgramDepth.mProgramId, "far");	
 }
 
 void Renderer::Shutdown() {
@@ -197,14 +205,24 @@ void Renderer::RenderGui() {
 	glBindFramebuffer(GL_FRAMEBUFFER, 0);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-	// Render the full screen quad
-	glUseProgram(mRenderQuadProgramColor.mProgramId);
-
 	glActiveTexture(GL_TEXTURE0);
-	glBindTexture(GL_TEXTURE_2D, mRenderTarget.mColorTexture);
-//	glBindTexture(GL_TEXTURE_2D, mRenderTarget.mDepthTexture);
-	glUniform1i(muRenderQuadTexture, 0);
-	glUniform1f(muRenderQuadTime, (float)(glfwGetTime() * 10.0f));
+
+	bool render_color = false;
+	
+	if (render_color) {
+		// Render the full screen quad
+		glUseProgram(mRenderQuadProgramColor.mProgramId);
+		glBindTexture(GL_TEXTURE_2D, mRenderTarget.mColorTexture);
+		glUniform1i(muRenderQuadTexture, 0);
+		glUniform1f(muRenderQuadTime, (float)(glfwGetTime() * 10.0f));
+	} else {
+		// render depth texture
+		glUseProgram(mRenderQuadProgramDepth.mProgramId);
+		glBindTexture(GL_TEXTURE_2D, mRenderTarget.mDepthTexture);
+		glUniform1i(muRenderQuadTexture, 0);
+		glUniform1f(muRenderQuadDepthNear, 1.0);
+		glUniform1f(muRenderQuadDepthFar, -1.0);
+	}
 
 	glEnableVertexAttribArray(0);
 	glBindBuffer(GL_ARRAY_BUFFER, mRenderQuadVertexBufferId);
diff --git a/src/modules/RenderModule.h b/src/modules/RenderModule.h
index 55dbc74..ac29df1 100644
--- a/src/modules/RenderModule.h
+++ b/src/modules/RenderModule.h
@@ -118,11 +118,15 @@ struct Renderer {
 
 	GLuint mRenderQuadVertexArrayId;
 	GLuint mRenderQuadVertexBufferId;
+
 	RenderProgram mRenderQuadProgramColor;
-	RenderProgram mRenderQuadProgramDepth;
 	GLuint muRenderQuadTexture;
 	GLuint muRenderQuadTime;
 
+	RenderProgram mRenderQuadProgramDepth;
+	GLuint muRenderQuadDepthNear;
+	GLuint muRenderQuadDepthFar;
+
 	Renderer() :
 		mInitialized(false),
 		mWidth (0),