Beco: Difference between revisions

Beco (view source)

Revision as of 18:50, 11 September 2018

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imported>Leoetlino

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 == Operations ==
-=== Getting the custom data for a given coordinate ===
+=== Getting data for a given coordinate ===
-{{expand section}}
+The algorithm that returns the custom data that is associated with a coordinate is very simple. It consists of determining the correct row index in the table, then iterating over segments in that row and returning the segment data when the X coordinate is within its bounds.
-At 0x7100E41C40 in Switch 1.5.0:
+For the reference, here is the official, mostly unreversed function<ref>0x7100E41C40 in Switch 1.5.0</ref> that implements the aforementioned algorithm:
 <syntaxhighlight lang="c++">
@@ Line 127: / Line 127: @@
    }
    return _entry->value;
+}
+</syntaxhighlight>
+A cleaner version of this algorithm is given below:
+<syntaxhighlight lang="c++">
+unsigned int eco::getCurrentAreaNum(float posX, float posZ, Ecosystem* unused, EcoMapInfo* info)
+{
+  posX = std::clamp(posX, -5000.0, 4999.0);
+  posZ = std::clamp(posZ, -4000.0, 4000.0);
+  float epsilon1 = (posX + 5000.0 < 0.0) ? -0.5 : 0.5;
+  float epsilon2 = (posZ + 4000.0 < 0.0) ? -0.5 : 0.5;
+  int x =  posX + 5000.0 + epsilon1;
+  int z = (posZ + 4000.0 + epsilon2) / info->header->divisor;
+  uint row = std::clamp(z, 0, info->header->numRows - 2);
+  if (divisor == 10)
+    x = x / 10 + ((0x66666667LL * x) >> 0x3F);
+  uint* offsets = &info->rowOffsets[row];
+  if ( offsets[0] >= offsets[1] )
+    return 0xFFFFFFFF;
+  Segment* segment = reinterpret_cast<Segment*>((char *)info->rows + 2 * offsets[0]);
+  Segment* segmentEnd = reinterpret_cast<Segment*>((char *)info->rows + 2 * offsets[1]);
+  uint totalLength = 0;
+  while (true)
+  {
+    totalLength += segment->length;
+    if (x < totalLength)
+      break;
+    ++segment;
+    if (segment >= segmentEnd)
+      return 0xFFFFFFFF;
+  }
+  return segment->value;
 }
 </syntaxhighlight>