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Beco (view source)

Revision as of 01:22, 24 November 2021

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→‎Getting data for a given coordinate: replace pseudocode with actual C++ source code (from the decomp project)
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(→‎Getting data for a given coordinate: replace pseudocode with actual C++ source code (from the decomp project))
 
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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.
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.


<div class="mw-collapsible mw-collapsed">
For the reference, here is the official, mostly unreversed function<ref>0x7100E41C40 in Switch 1.5.0</ref> that implements the aforementioned algorithm:
<div class="mw-collapsible-content">
<syntaxhighlight lang="c++">
<syntaxhighlight lang="c++">
unsigned int __fastcall eco::getCurrentAreaNum(float posX, float posZ, Ecosystem *ecosystem, EcoMapInfo *info)
s32 Ecosystem::getMapArea(const EcoMapInfo& info, f32 posX, f32 posZ) const {
{
    posX = sead::Mathf::clamp(posX, -5000.0f, 4999.0f);
  float _x; // s2
    posZ = sead::Mathf::clamp(posZ, -4000.0f, 4000.0f);
  float _z; // s0
  int divisor; // w10
  int numEntries; // w12
  float v8; // s4
  signed int c_x; // w8
  float v10; // s0
  float v11; // s1
  int c_z; // w9
  int idx; // w9
  u32 *v14; // x9
  __int64 v15; // x10
  __int64 v16; // x11
  EcoMapEntry *tables; // x12
  EcoMapEntry *_entryEnd; // x11
  EcoMapEntry *_entry; // x10
  signed int totalLength; // w9
  unsigned int result; // w0


  _x = -5000.0;
    const auto epsilon = [](float n) { return n >= 0.0f ? 0.5f : -0.5f; };
  if ( posX >= -5000.0 )
  {
    _x = posX;
    if ( posX > 4999.0 )
      _x = 4999.0;
  }
  _z = -4000.0;
  if ( posZ >= -4000.0 )
  {
    _z = posZ;
    if ( posZ > 4000.0 )
      _z = 4000.0;
  }


  divisor = info->map->divisor;
    s32 x = s32(posX + 5000.0f + epsilon(posX + 5000.0f));
  numEntries = info->map->numTables - 2;
     s32 z = s32(posZ + 4000.0f + epsilon(posZ + 4000.0f)) / info.mHeader->divisor;
  if ( (float)(_x + 5000.0) < 0.0 )
     s32 row = sead::Mathi::clamp(z, 0, info.mHeader->num_rows - 2);
    v8 = -0.5;
  else
     v8 = 0.5;
  c_x = (signed int)(float)((float)(_x + 5000.0) + v8);
  v10 = _z + 4000.0;
  if ( v10 < 0.0 )
    v11 = -0.5;
  else
    v11 = 0.5;
  c_z = (signed int)(float)(v10 + v11) / divisor;
  if ( c_z <= numEntries )
     numEntries = (signed int)(float)(v10 + v11) / divisor;
  if ( c_z >= 0 )
    idx = numEntries;
  else
    idx = 0;


  v14 = &info->tableOffsets[idx];
    if (info.mHeader->divisor == 10)
  if ( divisor == 0xA )
        x /= 10;
    c_x = (0x66666667LL * c_x >> 0x22) + ((unsigned __int64)(0x66666667LL * c_x) >> 0x3F);
  v15 = (signed int)*v14;
  v16 = (signed int)v14[1];
  if ( (signed int)v15 >= (signed int)v16 )
    return 0xFFFFFFFF;


  tables = info->tables;
    if (info.mRowOffsets[row] >= info.mRowOffsets[row + 1])
  _entryEnd = (EcoMapEntry *)((char *)tables + 2 * v16);
        return -1;
  _entry = (EcoMapEntry *)((char *)tables + 2 * v15);
 
  totalLength = 0;
    auto* segmentEnd = reinterpret_cast<const Segment*>(info.mRows + 2 * info.mRowOffsets[row + 1]);
  result = 0xFFFFFFFF;
    auto* segment = reinterpret_cast<const Segment*>(info.mRows + 2 * info.mRowOffsets[row]);
  while ( 1 )
    s32 totalLength = 0;
  {
    while (true) {
    totalLength += _entry->length;
        totalLength += segment->length;
    if ( c_x < totalLength )
        if (x < totalLength)
      break;
            break;
    ++_entry;
        ++segment;
    if ( _entry >= _entryEnd )
        if (segment >= segmentEnd)
      return result;
            return -1;
  }
    }
  return _entry->value;
    return segment->value;
}
}
</syntaxhighlight>
</syntaxhighlight>
</div>
</div>
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 (info->header->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]);
Source: https://github.com/zeldaret/botw/blob/022f029db1ef03d900fb54bad0807939c9695720/src/KingSystem/Ecosystem/ecoSystem.cpp#L100
  Segment* segmentEnd = reinterpret_cast<Segment*>((char *)info->rows + 2 * offsets[1]);
  uint totalLength = 0;
  while (true)
  {
    totalLength += segment->length;
    if (x < totalLength)
      return segment->value;
    ++segment;
    if (segment >= segmentEnd)
      return 0xFFFFFFFF;
  }
}
</syntaxhighlight>


== Usage in ''Breath of the Wild'' ==
== Usage in ''Breath of the Wild'' ==
Retrieved from "https://zeldamods.org/wiki/Special:MobileDiff/11034"

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