diff --git a/vtm/src/org/oscim/layers/tile/VectorTileRenderer.java b/vtm/src/org/oscim/layers/tile/VectorTileRenderer.java
index 6dec218b..48f95ce9 100644
--- a/vtm/src/org/oscim/layers/tile/VectorTileRenderer.java
+++ b/vtm/src/org/oscim/layers/tile/VectorTileRenderer.java
@@ -43,18 +43,25 @@ public class VectorTileRenderer extends TileRenderer {
 		mViewProj.setValue(14, 0);
 		mViewProj.multiplyRhs(v.view);
 
-		mClipMode = 1;
+		mClipMode = PolygonLayer.CLIP_STENCIL;
 
 		/* */
 		int tileCnt = mDrawTiles.cnt + mProxyTileCnt;
 		MapTile[] tiles = mDrawTiles.tiles;
 
+		boolean drawProxies = false;
+
 		for (int i = 0; i < tileCnt; i++) {
 			MapTile t = tiles[i];
 			if (t.isVisible && t.state != READY) {
 				GL.glDepthMask(true);
 				GL.glClear(GL20.GL_DEPTH_BUFFER_BIT);
-				mClipMode = 2;
+
+				/* always write depth for non-proxy tiles */
+				GL.glDepthFunc(GL20.GL_ALWAYS);
+
+				mClipMode = PolygonLayer.CLIP_DEPTH;
+				drawProxies = true;
 				break;
 			}
 		}
@@ -71,8 +78,8 @@ public class VectorTileRenderer extends TileRenderer {
 		 * have data yet. Proxies are clipped to the region where nothing
 		 * was drawn to depth buffer.
 		 * TODO draw proxies for placeholder */
-		if (mClipMode > 1) {
-			mClipMode = 3;
+		if (drawProxies) {
+			/* only draw where no other tile is drawn */
 			GL.glDepthFunc(GL20.GL_LESS);
 
 			/* draw child or parent proxies */
diff --git a/vtm/src/org/oscim/renderer/elements/PolygonLayer.java b/vtm/src/org/oscim/renderer/elements/PolygonLayer.java
index fe40349a..ed6da716 100644
--- a/vtm/src/org/oscim/renderer/elements/PolygonLayer.java
+++ b/vtm/src/org/oscim/renderer/elements/PolygonLayer.java
@@ -42,6 +42,9 @@ import org.slf4j.LoggerFactory;
 public final class PolygonLayer extends RenderElement {
 	static final Logger log = LoggerFactory.getLogger(PolygonLayer.class);
 
+	public final static int CLIP_STENCIL = 1;
+	public final static int CLIP_DEPTH = 2;
+
 	private static final float S = MapRenderer.COORD_SCALE;
 
 	private static final boolean enableTexture = true;
@@ -274,6 +277,7 @@ public final class PolygonLayer extends RenderElement {
 		 *            pass true to clear stencil buffer region
 		 * @param clipMode
 		 *            clip to first quad in current vbo
+		 *            using CLIP_STENCIL / CLIP_DEPTH
 		 * 
 		 * @return
 		 *         next layer
@@ -366,47 +370,43 @@ public final class PolygonLayer extends RenderElement {
 		 */
 		static void drawStencilRegion(boolean first, int clipMode) {
 
-			// disable drawing to color buffer
+			/* disable drawing to color buffer */
 			GL.glColorMask(false, false, false, false);
 
-			// write to all stencil bits
+			/* write to all stencil bits */
 			GL.glStencilMask(0xFF);
 
 			if (first) {
-				// clear previous clip-region from stencil buffer
-				//GL.glClear(GL20.GL_STENCIL_BUFFER_BIT);
+				/* Draw clip-region into depth and stencil buffer.
+				 * This is used for tile line and polygon layers.
+				 * 
+				 * Together with depth test (GL_LESS) this ensures to
+				 * only draw where no other tile has drawn yet. */
 
-				// Draw clip-region into depth and stencil buffer
-				// this is used for tile line and polygon layers.
-				// Depth offset is increased for each tile. Together
-				// with depth test (GL_LESS) this ensures to only
-				// draw where no other tile has drawn yet.
-				//GL.glEnable(GL20.GL_POLYGON_OFFSET_FILL);
-				if (clipMode > 1) {
-					// test GL_LESS and write to depth buffer
+				if (clipMode == CLIP_DEPTH) {
+					/* test GL_LESS/GL_ALWAYS to write to depth buffer */
 					GLState.test(true, true);
 					GL.glDepthMask(true);
 				}
 
-				// always pass stencil test and set clip bit
+				/* always pass stencil test and set clip bit */
 				GL.glStencilFunc(GL20.GL_ALWAYS, CLIP_BIT, 0x00);
 			} else {
-				// use clip bit from stencil buffer
-				// to clear stencil 'layer-bits' (0x7f)
+				/* use clip bit from stencil buffer to clear stencil
+				 * 'layer-bits' (0x7f) */
 				GL.glStencilFunc(GL20.GL_EQUAL, CLIP_BIT, CLIP_BIT);
 			}
 
-			// set clip bit (0x80) for draw region
+			/* set clip bit (0x80) for draw region */
 			GL.glStencilOp(GL20.GL_KEEP, GL20.GL_KEEP, GL20.GL_REPLACE);
 
-			// draw a quad for the tile region
+			/* draw a quad for the tile region */
 			GL.glDrawArrays(GL20.GL_TRIANGLE_STRIP, 0, 4);
 
 			if (first) {
-				if (clipMode > 1) {
-					// dont modify depth buffer
+				if (clipMode == CLIP_DEPTH) {
+					/* dont modify depth buffer */
 					GL.glDepthMask(false);
-					// test only stencil
 					GLState.test(false, true);
 				}
 				GL.glStencilFunc(GL20.GL_EQUAL, CLIP_BIT, CLIP_BIT);
@@ -416,7 +416,7 @@ public final class PolygonLayer extends RenderElement {
 		/**
 		 * Clear stencilbuffer for a tile region by drawing
 		 * a quad with func 'always' and op 'zero'. Using 'color'
-		 * and 'alpha' for a fake fade effect.
+		 * and 'alpha' to fake a fade effect.
 		 */
 		public static void drawOver(GLViewport v, int color, float alpha) {
 			setShader(polyShader, v);
@@ -425,20 +425,24 @@ public final class PolygonLayer extends RenderElement {
 				GLUtils.setColor(hPolygonColor[0], color, alpha);
 				GLState.blend(true);
 			} else {
-				// disable drawing to framebuffer (will be re-enabled in fill)
+				/* disable drawing to framebuffer (will be re-enabled in fill) */
 				GL.glColorMask(false, false, false, false);
 			}
-			// always pass stencil test:
-			//glStencilFunc(GL_ALWAYS, 0x00, 0x00);
+
+			// TODO always pass stencil test: <-- only if not proxy?
+			//GL.glStencilFunc(GL_ALWAYS, 0x00, 0x00);
+
 			GL.glStencilFunc(GL20.GL_EQUAL, CLIP_BIT, CLIP_BIT);
 
-			// write to all bits
+			/* write to all bits */
 			GL.glStencilMask(0xFF);
-			// zero out area to draw to
+
+			/* zero out area to draw to */
 			GL.glStencilOp(GL20.GL_KEEP, GL20.GL_KEEP, GL20.GL_ZERO);
 
 			GL.glDrawArrays(GL20.GL_TRIANGLE_STRIP, 0, 4);
 
+			// FIXME needed here?
 			if (color == 0)
 				GL.glColorMask(true, true, true, true);
 		}