S3DBLayer: use transparency of extrusion style (#556)

vtm/src/org/oscim/backend/canvas/Color.java

@@ -1,5 +1,6 @@
 /*
  * Copyright 2013 Hannes Janetzek
+ * Copyright 2018 Gustl22
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -115,6 +116,22 @@ public final class Color {
         return ((color) & 0xff);
     }
 
+    public static int setA(int color, int a) {
+        return ((a << 24) | (color & 0xffffff));
+    }
+
+    public static int setR(int color, int r) {
+        return ((r << 16) | (color & 0xff00ffff));
+    }
+
+    public static int setG(int color, int g) {
+        return ((g << 8) | (color & 0xffff00ff));
+    }
+
+    public static int setB(int color, int b) {
+        return (b | (color & 0xffffff00));
+    }
+
     public static int parseColorComponents(String str) {
         int numComponents = 4;
         int cur = 5;

vtm/src/org/oscim/layers/tile/buildings/S3DBLayer.java

@@ -15,6 +15,7 @@
  */
 package org.oscim.layers.tile.buildings;
 
+import org.oscim.backend.canvas.Color;
 import org.oscim.core.Box;
 import org.oscim.core.GeometryBuffer;
 import org.oscim.core.MapElement;
@@ -45,6 +46,7 @@ public class S3DBLayer extends BuildingLayer {
     private final float TILE_SCALE = (ExtrusionUtils.REF_TILE_SIZE / (Tile.SIZE * COORD_SCALE));
 
     private boolean mColored = true;
+    private boolean mTransparent = true;
 
     public S3DBLayer(Map map, VectorTileLayer tileLayer) {
         this(map, tileLayer, MIN_ZOOM, map.viewport().getMaxZoomLevel());
@@ -62,6 +64,17 @@ public class S3DBLayer extends BuildingLayer {
         mColored = colored;
     }
 
+    public boolean isTransparent() {
+        return mTransparent;
+    }
+
+    /**
+     * @param transparent if true it adopts transparency of extrusion styles
+     */
+    public void setTransparent(boolean transparent) {
+        mTransparent = transparent;
+    }
+
     @Override
     public void complete(MapTile tile, boolean success) {
         super.complete(tile, success);
@@ -137,6 +150,9 @@ public class S3DBLayer extends BuildingLayer {
 
         if (bColor == null) {
             bColor = extrusion.colorTop;
+        } else if (mTransparent) {
+            // Multiply alpha channel of extrusion style
+            bColor = ExtrusionStyle.blendAlpha(bColor, Color.aToFloat(extrusion.colorTop));
         }
 
         // Scale x, y and z axis
@@ -238,9 +254,14 @@ public class S3DBLayer extends BuildingLayer {
 
         GeometryBuffer gElement = new GeometryBuffer(element);
         GeometryBuffer specialParts = null;
-        if (roofColor == null) roofColor = buildingColor;
+        if (roofColor == null)
-        boolean success = false;
+            roofColor = buildingColor;
+        else if (mTransparent) {
+            // For simplicity use transparency of building, which is identical in nearly all cases
+            roofColor = ExtrusionStyle.blendAlpha(roofColor, Color.aToFloat(buildingColor));
+        }
 
+        boolean success;
         switch (v) {
             case Tag.VALUE_DOME:
             case Tag.VALUE_ONION:

vtm/src/org/oscim/theme/styles/ExtrusionStyle.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2013 Hannes Janetzek
  * Copyright 2016-2017 devemux86
+ * Copyright 2018 Gustl22
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -56,6 +57,20 @@ public class ExtrusionStyle extends RenderStyle<ExtrusionStyle> {
         this.defaultHeight = b.defaultHeight;
     }
 
+    public static int blendAlpha(int color, float alpha) {
+        if (alpha == 1.0f)
+            return color;
+        return Color.setA(color, (int) (Color.a(color) * alpha));
+    }
+
+    public static void blendAlpha(float colors[], float alpha) {
+        if (alpha == 1.0f)
+            return;
+        for (int i = 0; i < colors.length; i++) {
+            colors[i] = alpha * colors[i];
+        }
+    }
+
     public static void fillColors(int side, int top, int line, float[] colors) {
         float a = Color.aToFloat(top);
         colors[0] = a * Color.rToFloat(top);