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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. |
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| <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'' == |