text: /*
  ---------------------------------------------------------------------------
  Open Asset Import Library (assimp)
  ---------------------------------------------------------------------------
  
  Copyright (c) 2006-2020, assimp team
  
  
  
  All rights reserved.
  
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  with or without modification, are permitted provided that the following
  conditions are met:
  
  * Redistributions of source code must retain the above
    copyright notice, this list of conditions and the
    following disclaimer.
  
  * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the
    following disclaimer in the documentation and/or other
    materials provided with the distribution.
  
  * Neither the name of the assimp team, nor the names of its
    contributors may be used to endorse or promote products
    derived from this software without specific prior
    written permission of the assimp team.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  ---------------------------------------------------------------------------
  */
  
  /** @file Implementation of the Terragen importer class */
  
  
  
  #ifndef ASSIMP_BUILD_NO_TERRAGEN_IMPORTER
  
  #include "TerragenLoader.h"
  #include <assimp/StreamReader.h>
  #include <assimp/Importer.hpp>
  #include <assimp/IOSystem.hpp>
  #include <assimp/scene.h>
  #include <assimp/DefaultLogger.hpp>
  #include <assimp/importerdesc.h>
  
  using namespace Assimp;
  
  static const aiImporterDesc desc = {
      "Terragen Heightmap Importer",
      "",
      "",
      "http://www.planetside.co.uk/",
      aiImporterFlags_SupportBinaryFlavour,
      0,
      0,
      0,
      0,
      "ter"
  };
  
  // ------------------------------------------------------------------------------------------------
  // Constructor to be privately used by Importer
  TerragenImporter::TerragenImporter()
  : configComputeUVs (false)
  {}
  
  // ------------------------------------------------------------------------------------------------
  // Destructor, private as well
  TerragenImporter::~TerragenImporter()
  {}
  
  // ------------------------------------------------------------------------------------------------
  // Returns whether the class can handle the format of the given file.
  bool TerragenImporter::CanRead( const std::string& pFile, IOSystem* pIOHandler, bool checkSig) const
  {
      // check file extension
      std::string extension = GetExtension(pFile);
  
      if( extension == "ter")
          return true;
  
      if(  !extension.length() || checkSig)   {
          /*  If CanRead() is called in order to check whether we
           *  support a specific file extension in general pIOHandler
           *  might be NULL and it's our duty to return true here.
           */
          if (!pIOHandler)return true;
          const char* tokens[] = {"terragen"};
          return SearchFileHeaderForToken(pIOHandler,pFile,tokens,1);
      }
      return false;
  }
  
  // ------------------------------------------------------------------------------------------------
  // Build a string of all file extensions supported
  const aiImporterDesc* TerragenImporter::GetInfo () const
  {
      return &desc;
  }
  
  // ------------------------------------------------------------------------------------------------
  // Setup import properties
  void TerragenImporter::SetupProperties(const Importer* pImp)
  {
      // AI_CONFIG_IMPORT_TER_MAKE_UVS
      configComputeUVs = ( 0 != pImp->GetPropertyInteger(AI_CONFIG_IMPORT_TER_MAKE_UVS,0) );
  }
  
  // ------------------------------------------------------------------------------------------------
  // Imports the given file into the given scene structure.
  void TerragenImporter::InternReadFile( const std::string& pFile,
      aiScene* pScene, IOSystem* pIOHandler)
  {
      IOStream* file = pIOHandler->Open( pFile, "rb");
  
      // Check whether we can read from the file
      if( file == NULL)
          throw DeadlyImportError( "Failed to open TERRAGEN TERRAIN file " + pFile + ".");
  
      // Construct a stream reader to read all data in the correct endianness
      StreamReaderLE reader(file);
      if(reader.GetRemainingSize() < 16)
          throw DeadlyImportError( "TER: file is too small" );
  
      // Check for the existence of the two magic strings 'TERRAGEN' and 'TERRAIN '
      if (::strncmp((const char*)reader.GetPtr(),AI_TERR_BASE_STRING,8))
          throw DeadlyImportError( "TER: Magic string \'TERRAGEN\' not found" );
  
      if (::strncmp((const char*)reader.GetPtr()+8,AI_TERR_TERRAIN_STRING,8))
          throw DeadlyImportError( "TER: Magic string \'TERRAIN\' not found" );
  
      unsigned int x = 0,y = 0,mode = 0;
  
      aiNode* root = pScene->mRootNode = new aiNode();
      root->mName.Set("<TERRAGEN.TERRAIN>");
  
      // Default scaling is 30
      root->mTransformation.a1 = root->mTransformation.b2 = root->mTransformation.c3 = 30.f;
  
      // Now read all chunks until we're finished or an EOF marker is encountered
      reader.IncPtr(16);
      while (reader.GetRemainingSize() >= 4)
      {
          const char* head = (const char*)reader.GetPtr();
          reader.IncPtr(4);
  
          // EOF, break in every case
          if (!::strncmp(head,AI_TERR_EOF_STRING,4))
              break;
  
          // Number of x-data points
          if (!::strncmp(head,AI_TERR_CHUNK_XPTS,4))
          {
              x = (uint16_t)reader.GetI2();
          }
          // Number of y-data points
          else if (!::strncmp(head,AI_TERR_CHUNK_YPTS,4))
          {
              y = (uint16_t)reader.GetI2();
          }
          // Squared terrains width-1.
          else if (!::strncmp(head,AI_TERR_CHUNK_SIZE,4))
          {
              x = y = (uint16_t)reader.GetI2()+1;
          }
          // terrain scaling
          else if (!::strncmp(head,AI_TERR_CHUNK_SCAL,4))
          {
              root->mTransformation.a1 = reader.GetF4();
              root->mTransformation.b2 = reader.GetF4();
              root->mTransformation.c3 = reader.GetF4();
          }
          // mapping == 1: earth radius
          else if (!::strncmp(head,AI_TERR_CHUNK_CRAD,4))
          {
              reader.GetF4();
          }
          // mapping mode
          else if (!::strncmp(head,AI_TERR_CHUNK_CRVM,4))
          {
              mode = reader.GetI1();
              if (0 != mode)
                  ASSIMP_LOG_ERROR("TER: Unsupported mapping mode, a flat terrain is returned");
          }
          // actual terrain data
          else if (!::strncmp(head,AI_TERR_CHUNK_ALTW,4))
          {
              float hscale  = (float)reader.GetI2()  / 65536;
              float bheight = (float)reader.GetI2();
  
              if (!hscale)hscale = 1;
  
              // Ensure we have enough data
              if (reader.GetRemainingSize() < x*y*2)
                  throw DeadlyImportError("TER: ALTW chunk is too small");
  
              if (x <= 1 || y <= 1)
                  throw DeadlyImportError("TER: Invalid terrain size");
  
              // Allocate the output mesh
              pScene->mMeshes = new aiMesh*[pScene->mNumMeshes = 1];
              aiMesh* m = pScene->mMeshes[0] = new aiMesh();
  
              // We return quads
              aiFace* f = m->mFaces = new aiFace[m->mNumFaces = (x-1)*(y-1)];
              aiVector3D* pv = m->mVertices = new aiVector3D[m->mNumVertices = m->mNumFaces*4];
  
              aiVector3D *uv( NULL );
              float step_y( 0.0f ), step_x( 0.0f );
              if (configComputeUVs) {
                  uv = m->mTextureCoords[0] = new aiVector3D[m->mNumVertices];
                  step_y = 1.f/y;
                  step_x = 1.f/x;
              }
              const int16_t* data = (const int16_t*)reader.GetPtr();
  
              for (unsigned int yy = 0, t = 0; yy < y-1;++yy) {
                  for (unsigned int xx = 0; xx < x-1;++xx,++f)    {
  
                      // make verts
                      const float fy = (float)yy, fx = (float)xx;
                      unsigned tmp,tmp2;
                      *pv++ = aiVector3D(fx,fy,    (float)data[(tmp2=x*yy)    + xx] * hscale + bheight);
                      *pv++ = aiVector3D(fx,fy+1,  (float)data[(tmp=x*(yy+1)) + xx] * hscale + bheight);
                      *pv++ = aiVector3D(fx+1,fy+1,(float)data[tmp  + xx+1]         * hscale + bheight);
                      *pv++ = aiVector3D(fx+1,fy,  (float)data[tmp2 + xx+1]         * hscale + bheight);
  
                      // also make texture coordinates, if necessary
                      if (configComputeUVs) {
                          *uv++ = aiVector3D( step_x*xx,     step_y*yy,     0.f );
                          *uv++ = aiVector3D( step_x*xx,     step_y*(yy+1), 0.f );
                          *uv++ = aiVector3D( step_x*(xx+1), step_y*(yy+1), 0.f );
                          *uv++ = aiVector3D( step_x*(xx+1), step_y*yy,     0.f );
                      }
  
                      // make indices
                      f->mIndices = new unsigned int[f->mNumIndices = 4];
                      for (unsigned int i = 0; i < 4;++i)
                          f->mIndices[i] = t++;
                  }
              }
  
              // Add the mesh to the root node
              root->mMeshes = new unsigned int[root->mNumMeshes = 1];
              root->mMeshes[0] = 0;
          }
  
          // Get to the next chunk (4 byte aligned)
          unsigned dtt;
          if ((dtt = reader.GetCurrentPos() & 0x3))
              reader.IncPtr(4-dtt);
      }
  
      // Check whether we have a mesh now
      if (pScene->mNumMeshes != 1)
          throw DeadlyImportError("TER: Unable to load terrain");
  
      // Set the AI_SCENE_FLAGS_TERRAIN bit
      pScene->mFlags |= AI_SCENE_FLAGS_TERRAIN;
  }
  
  #endif // !! ASSIMP_BUILD_NO_TERRAGEN_IMPORTER
  