Only one place where the size is defined

VoxelSpace.html

@@ -111,8 +111,11 @@
 
 var map =
 {
-    height: new Uint8Array(1024*1024), // 1024*1024 byte array with height information
-    color:  new Uint32Array(1024*1024) // 1024*1024 int array with RGB colors
+    width:    1024,
+    height:   1024,
+    shift:    10,  // power of two: 2^10 = 1024
+    altitude: new Uint8Array(1024*1024), // 1024 * 1024 byte array with height information
+    color:    new Uint32Array(1024*1024) // 1024 * 1024 int array with RGB colors
 };
 
 // ---------------------------------------------
@@ -188,8 +191,8 @@
     }
 
     // Collision detection. Don't fly below the surface.
-    var mapoffset = ((Math.floor(camera.y) & 1023) << 10) + (Math.floor(camera.x) & 1023)|0;
-    if ((map.height[mapoffset]+10) > camera.height) camera.height = map.height[mapoffset] + 10;
+    var mapoffset = ((Math.floor(camera.y) & (map.width-1)) << map.shift) + (Math.floor(camera.x) & (map.height-1))|0;
+    if ((map.altitude[mapoffset]+10) > camera.height) camera.height = map.altitude[mapoffset] + 10;
 
     time = current;
 
@@ -374,6 +377,9 @@
 
 function Render()
 {
+    var mapwidthperiod = map.width - 1;
+    var mapheightperiod = map.height - 1;
+
     var screenwidth = screen.canvas.width|0;
     var sinang = Math.sin(camera.angle);
     var cosang = Math.cos(camera.angle);
@@ -400,8 +406,8 @@
         var invz = 1. / z * 240.;
         for(var i=0; i<screenwidth|0; i=i+1|0)
         {
-            var mapoffset = ((Math.floor(ply) & 1023) << 10) + (Math.floor(plx) & 1023)|0;
-            var heightonscreen = (camera.height - map.height[mapoffset]) * invz + camera.horizon|0;
+            var mapoffset = ((Math.floor(ply) & mapwidthperiod) << map.shift) + (Math.floor(plx) & mapheightperiod)|0;
+            var heightonscreen = (camera.height - map.altitude[mapoffset]) * invz + camera.horizon|0;
             DrawVerticalLine(i, heightonscreen|0, hiddeny[i], map.color[mapoffset]);
             if (heightonscreen < hiddeny[i]) hiddeny[i] = heightonscreen;
             plx += dx;
@@ -450,11 +456,10 @@
         image.onload = function() {
             var tempcanvas = document.createElement("canvas");
             var tempcontext = tempcanvas.getContext("2d");
-            tempcanvas.width = 1024;
-            tempcanvas.height = 1024;
-            tempcontext.drawImage(image, 0, 0, 1024, 1024 );
-
-            result[i] = tempcontext.getImageData(0, 0, 1024, 1024).data;
+            tempcanvas.width = map.width;
+            tempcanvas.height = map.height;
+            tempcontext.drawImage(image, 0, 0, map.width, map.height);
+            result[i] = tempcontext.getImageData(0, 0, map.width, map.height).data;
             pending--;
             if (pending === 0) {
                 OnSuccess(result);
@@ -474,10 +479,10 @@
 {
     var datac = result[0];
     var datah = result[1];
-    for(var i=0; i<1024*1024; i++)
+    for(var i=0; i<map.width*map.height; i++)
     {
         map.color[i] = 0xFF000000 | (datac[(i<<2) + 2] << 16) | (datac[(i<<2) + 1] << 8) | datac[(i<<2) + 0];
-        map.height[i] = datah[i<<2];
+        map.altitude[i] = datah[i<<2];
     }
     Draw();
 }
@@ -505,10 +510,10 @@
 
 function Init()
 {
-    for(var i=0; i<1024*1024; i++)
+    for(var i=0; i<map.width*map.height; i++)
     {
         map.color[i] = 0xFF007050;
-        map.height[i] = 0;
+        map.altitude[i] = 0;
     }
 
     LoadMap("C1W;D1");