Ticket #1707: spatial_optimization.patch

source/simulation2/helpers/Spatial.h

@@ -210 +210 @@
      */
     std::vector<T> GetNear(CFixedVector2D pos, entity_pos_t range)
     {
-        // TODO: be cleverer and return a circular pattern of divisions,
-        // not this square over-approximation
+        std::vector<T> ret;
 
-        return GetInRange(pos - CFixedVector2D(range, range), pos + CFixedVector2D(range, range));
+        ENSURE(range >= entity_pos_t::FromInt(0));
+
+        u32 i0 = GetI0(pos.X - range);
+        u32 j0 = GetJ0(pos.Y - range);
+        u32 i1 = GetI1(pos.X + range);
+        u32 j1 = GetJ1(pos.Y + range);
+        for (u32 j = j0; j <= j1; ++j)
+        {
+            for (u32 i = i0; i <= i1; ++i)
+            {
+                std::vector<T>& div = m_Divisions.at(i + j*m_DivisionsW);
+                if (!div.empty())
+                {
+                    if (OverlapBoxCircle(GetPos0(i,j), GetPos1(i,j), pos, range))
+                    {
+                        ret.insert(ret.end(), div.begin(), div.end());
+                    }
+                }
+            }
+        }
+
+        // Remove duplicates
+        std::sort(ret.begin(), ret.end());
+        ret.erase(std::unique(ret.begin(), ret.end()), ret.end());
+
+        return ret;
     }
 
 private:
@@ -251 +275 @@
         return GetI1(pos.X) + GetJ1(pos.Y)*m_DivisionsW;
     }
 
+    // Helper functions for translating division indexes into the coordinates 
+    // of the corresponding division rectangle.
+    CFixedVector2D GetPos0(u32 i, u32 j)
+    {
+        return CFixedVector2D(m_DivisionSize * (int)i, m_DivisionSize * (int)j);
+    }
+    
+    CFixedVector2D GetPos1(u32 i, u32 j)
+    {
+        return CFixedVector2D(m_DivisionSize * (int)(i+1), m_DivisionSize * (int)(j+1));
+    }
+
+    // Helper function to determine whether (the area of) an axis aligned box specified 
+    // by posMin and posMax overlaps with (the area of) a circle defined by center and radius.
+    bool OverlapBoxCircle(CFixedVector2D posMin, CFixedVector2D posMax, CFixedVector2D c, entity_pos_t r)
+    {
+        // distance of c from X/Y slab corresponding to the box (negative if inside)
+        entity_pos_t distX = std::max(posMin.X - c.X, c.X - posMax.X);
+        entity_pos_t distY = std::max(posMin.Y - c.Y, c.Y - posMax.Y);
+
+        if (distX <= entity_pos_t::Zero())
+        {
+            // within X slab; overlap if not too far from Y-boundary of box
+            return distY <= r;
+        }
+        else if (distY <= entity_pos_t::Zero())
+        {
+            // within Y slab; overlap if not too far from X-boundary of box
+            return distX <= r;
+        }
+        else
+        {
+            // neither within X or Y slab; overlap if not too far from corner point
+            return CFixedVector2D(distX, distY).CompareLength(r) <= 0;
+        }
+    }
+
     entity_pos_t m_DivisionSize;
     std::vector<std::vector<T> > m_Divisions;
     u32 m_DivisionsW;