From d3c31199f14a4b5b0732742f215d68282a2076a3 Mon Sep 17 00:00:00 2001
From: Hannes Janetzek <hannes.janetzek@gmail.com>
Date: Wed, 3 Apr 2013 14:35:24 +0200
Subject: [PATCH] adapt building height to ground resolution

---
 src/org/oscim/generator/TileGenerator.java      | 14 +++++++++++---
 .../oscim/renderer/layer/ExtrusionLayer.java    | 17 ++++++++++++++---
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/org/oscim/generator/TileGenerator.java b/src/org/oscim/generator/TileGenerator.java
index 2129f969..74e58623 100644
--- a/src/org/oscim/generator/TileGenerator.java
+++ b/src/org/oscim/generator/TileGenerator.java
@@ -106,6 +106,7 @@ public class TileGenerator implements IRenderCallback, IMapDatabaseCallback {
 
 	private float mStrokeScale = 1.0f;
 	private float mLatScaleFactor;
+	private float mGroundResolution;
 
 	// replacement for variable value tags that should not be matched by RenderTheme
 	private final static Tag mTagEmptyName = new Tag(Tag.TAG_KEY_NAME, null, false);
@@ -150,8 +151,15 @@ public class TileGenerator implements IRenderCallback, IMapDatabaseCallback {
 		setScaleStrokeWidth(mTile.zoomLevel);
 
 		// account for area changes with latitude
-		mLatScaleFactor = 0.5f + 0.5f * ((float) Math.sin(Math.abs(MercatorProjection
-				.pixelYToLatitude(mTile.pixelY, mTile.zoomLevel)) * (Math.PI / 180)));
+		double latitude = MercatorProjection.pixelYToLatitude(mTile.pixelY + (Tile.TILE_SIZE >> 1),
+				mTile.zoomLevel);
+		mLatScaleFactor = 0.5f + 0.5f * ((float) Math.sin(Math.abs(latitude) * (Math.PI / 180)));
+
+		mGroundResolution = (float) (Math.cos(latitude * (Math.PI / 180))
+				* MercatorProjection.EARTH_CIRCUMFERENCE
+				/ ((long) Tile.TILE_SIZE << mTile.zoomLevel));
+
+		Log.d(TAG, mTile + " " + mGroundResolution);
 
 		mTile.layers = new Layers();
 
@@ -409,7 +417,7 @@ public class TileGenerator implements IRenderCallback, IMapDatabaseCallback {
 		if (mRenderBuildingModel) {
 			//Log.d(TAG, "add buildings: " + mTile + " " + mPriority);
 			if (mTile.layers.extrusionLayers == null)
-				mTile.layers.extrusionLayers = new ExtrusionLayer(0);
+				mTile.layers.extrusionLayers = new ExtrusionLayer(0, mGroundResolution);
 
 			((ExtrusionLayer) mTile.layers.extrusionLayers).addBuildings(mWay);
 
diff --git a/src/org/oscim/renderer/layer/ExtrusionLayer.java b/src/org/oscim/renderer/layer/ExtrusionLayer.java
index 91e8a7a1..e1670d7c 100644
--- a/src/org/oscim/renderer/layer/ExtrusionLayer.java
+++ b/src/org/oscim/renderer/layer/ExtrusionLayer.java
@@ -58,11 +58,13 @@ public class ExtrusionLayer extends Layer {
 	private final static int IND_OUTLINE = 3;
 
 	public boolean compiled = false;
+	private final float mGroundResolution;
 
-	public ExtrusionLayer(int level) {
+	public ExtrusionLayer(int level, float groundResolution) {
 		this.type = Layer.EXTRUSION;
 		this.level = level;
 
+		mGroundResolution = groundResolution;
 		mVertices = mCurVertices = VertexPool.get();
 
 		mIndices = new VertexPoolItem[4];
@@ -89,11 +91,20 @@ public class ExtrusionLayer extends Layer {
 		if (height == 0)
 			height = 12 * 100;
 
-		// 5 cm steps
-		float sfactor = (400f / Tile.TILE_SIZE) / 5f;
+		// 10 cm steps
+		float sfactor = 1 / 10f;
 		height *= sfactor;
 		minHeight *= sfactor;
 
+		// match height with ground resultion
+		// (meter per pixel)
+		height /= mGroundResolution;
+		minHeight /= mGroundResolution;
+
+		// my preference
+		height *= 0.85;
+		minHeight *= 0.85;
+
 		int length = 0;
 		for (int ipos = 0, ppos = 0, n = way.geom.index.length; ipos < n; ipos++, ppos += length) {
 			length = way.geom.index[ipos];