text: /** Helper structures for the Collada loader */
  
  /*
  Open Asset Import Library (assimp)
  ----------------------------------------------------------------------
  
  Copyright (c) 2006-2019, assimp team
  
  
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  following conditions are met:
  
  * Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.
  
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  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
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  contributors may be used to endorse or promote products
  derived from this software without specific prior
  written permission of the assimp team.
  
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  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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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.
  
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  */
  
  #ifndef AI_COLLADAHELPER_H_INC
  #define AI_COLLADAHELPER_H_INC
  
  #include <map>
  #include <vector>
  #include <stdint.h>
  #include <assimp/light.h>
  #include <assimp/mesh.h>
  #include <assimp/material.h>
  
  struct aiMaterial;
  
  namespace Assimp    {
  namespace Collada       {
  
  /** Collada file versions which evolved during the years ... */
  enum FormatVersion
  {
      FV_1_5_n,
      FV_1_4_n,
      FV_1_3_n
  };
  
  
  /** Transformation types that can be applied to a node */
  enum TransformType
  {
      TF_LOOKAT,
      TF_ROTATE,
      TF_TRANSLATE,
      TF_SCALE,
      TF_SKEW,
      TF_MATRIX
  };
  
  /** Different types of input data to a vertex or face */
  enum InputType
  {
      IT_Invalid,
      IT_Vertex,  // special type for per-index data referring to the <vertices> element carrying the per-vertex data.
      IT_Position,
      IT_Normal,
      IT_Texcoord,
      IT_Color,
      IT_Tangent,
      IT_Bitangent
  };
  
  /** Supported controller types */
  enum ControllerType
  {
      Skin,
      Morph
  };
  
  /** Supported morph methods */
  enum MorphMethod
  {
      Normalized,
      Relative
  };
  
  
  /** Contains all data for one of the different transformation types */
  struct Transform
  {
      std::string mID;  ///< SID of the transform step, by which anim channels address their target node
      TransformType mType;
      ai_real f[16]; ///< Interpretation of data depends on the type of the transformation
  };
  
  /** A collada camera. */
  struct Camera
  {
      Camera()
          :   mOrtho  (false)
          ,   mHorFov (10e10f)
          ,   mVerFov (10e10f)
          ,   mAspect (10e10f)
          ,   mZNear  (0.1f)
          ,   mZFar   (1000.f)
      {}
  
      // Name of camera
      std::string mName;
  
      // True if it is an orthografic camera
      bool mOrtho;
  
      //! Horizontal field of view in degrees
      ai_real mHorFov;
  
      //! Vertical field of view in degrees
      ai_real mVerFov;
  
      //! Screen aspect
      ai_real mAspect;
  
      //! Near& far z
      ai_real mZNear, mZFar;
  };
  
  #define ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET 1e9f
  
  /** A collada light source. */
  struct Light
  {
      Light()
          :   mType            (aiLightSource_UNDEFINED)
          ,   mAttConstant     (1.f)
          ,   mAttLinear       (0.f)
          ,   mAttQuadratic    (0.f)
          ,   mFalloffAngle    (180.f)
          ,   mFalloffExponent (0.f)
          ,   mPenumbraAngle   (ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET)
          ,   mOuterAngle      (ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET)
          ,   mIntensity       (1.f)
      {}
  
      //! Type of the light source aiLightSourceType + ambient
      unsigned int mType;
  
      //! Color of the light
      aiColor3D mColor;
  
      //! Light attenuation
      ai_real mAttConstant,mAttLinear,mAttQuadratic;
  
      //! Spot light falloff
      ai_real mFalloffAngle;
      ai_real mFalloffExponent;
  
      // -----------------------------------------------------
      // FCOLLADA extension from here
  
      //! ... related stuff from maja and max extensions
      ai_real mPenumbraAngle;
      ai_real mOuterAngle;
  
      //! Common light intensity
      ai_real mIntensity;
  };
  
  /** Short vertex index description */
  struct InputSemanticMapEntry
  {
      InputSemanticMapEntry()
          :   mSet(0)
          ,   mType(IT_Invalid)
      {}
  
      //! Index of set, optional
      unsigned int mSet;
  
      //! Type of referenced vertex input
      InputType mType;
  };
  
  /** Table to map from effect to vertex input semantics */
  struct SemanticMappingTable
  {
      //! Name of material
      std::string mMatName;
  
      //! List of semantic map commands, grouped by effect semantic name
      std::map<std::string, InputSemanticMapEntry> mMap;
  
      //! For std::find
      bool operator == (const std::string& s) const {
          return s == mMatName;
      }
  };
  
  /** A reference to a mesh inside a node, including materials assigned to the various subgroups.
   * The ID refers to either a mesh or a controller which specifies the mesh
   */
  struct MeshInstance
  {
      ///< ID of the mesh or controller to be instanced
      std::string mMeshOrController;
  
      ///< Map of materials by the subgroup ID they're applied to
      std::map<std::string, SemanticMappingTable> mMaterials;
  };
  
  /** A reference to a camera inside a node*/
  struct CameraInstance
  {
       ///< ID of the camera
      std::string mCamera;
  };
  
  /** A reference to a light inside a node*/
  struct LightInstance
  {
       ///< ID of the camera
      std::string mLight;
  };
  
  /** A reference to a node inside a node*/
  struct NodeInstance
  {
       ///< ID of the node
      std::string mNode;
  };
  
  /** A node in a scene hierarchy */
  struct Node
  {
      std::string mName;
      std::string mID;
      std::string mSID;
      Node* mParent;
      std::vector<Node*> mChildren;
  
      /** Operations in order to calculate the resulting transformation to parent. */
      std::vector<Transform> mTransforms;
  
      /** Meshes at this node */
      std::vector<MeshInstance> mMeshes;
  
      /** Lights at this node */
      std::vector<LightInstance> mLights;
  
      /** Cameras at this node */
      std::vector<CameraInstance> mCameras;
  
      /** Node instances at this node */
      std::vector<NodeInstance> mNodeInstances;
  
      /** Root-nodes: Name of primary camera, if any */
      std::string mPrimaryCamera;
  
      //! Constructor. Begin with a zero parent
      Node()
      : mParent( nullptr ){
          // empty
      }
  
      //! Destructor: delete all children subsequently
      ~Node() {
          for( std::vector<Node*>::iterator it = mChildren.begin(); it != mChildren.end(); ++it)
              delete *it;
      }
  };
  
  /** Data source array: either floats or strings */
  struct Data
  {
      bool mIsStringArray;
      std::vector<ai_real> mValues;
      std::vector<std::string> mStrings;
  };
  
  /** Accessor to a data array */
  struct Accessor
  {
      size_t mCount;   // in number of objects
      size_t mSize;    // size of an object, in elements (floats or strings, mostly 1)
      size_t mOffset;  // in number of values
      size_t mStride;  // Stride in number of values
      std::vector<std::string> mParams; // names of the data streams in the accessors. Empty string tells to ignore.
      size_t mSubOffset[4]; // Suboffset inside the object for the common 4 elements. For a vector, that's XYZ, for a color RGBA and so on.
                            // For example, SubOffset[0] denotes which of the values inside the object is the vector X component.
      std::string mSource;   // URL of the source array
      mutable const Data* mData; // Pointer to the source array, if resolved. NULL else
  
      Accessor()
      {
          mCount = 0; mSize = 0; mOffset = 0; mStride = 0; mData = NULL;
          mSubOffset[0] = mSubOffset[1] = mSubOffset[2] = mSubOffset[3] = 0;
      }
  };
  
  /** A single face in a mesh */
  struct Face
  {
      std::vector<size_t> mIndices;
  };
  
  /** An input channel for mesh data, referring to a single accessor */
  struct InputChannel
  {
      InputType mType;      // Type of the data
      size_t mIndex;        // Optional index, if multiple sets of the same data type are given
      size_t mOffset;       // Index offset in the indices array of per-face indices. Don't ask, can't explain that any better.
      std::string mAccessor; // ID of the accessor where to read the actual values from.
      mutable const Accessor* mResolved; // Pointer to the accessor, if resolved. NULL else
  
      InputChannel() { mType = IT_Invalid; mIndex = 0; mOffset = 0; mResolved = NULL; }
  };
  
  /** Subset of a mesh with a certain material */
  struct SubMesh
  {
      std::string mMaterial; ///< subgroup identifier
      size_t mNumFaces; ///< number of faces in this submesh
  };
  
  /** Contains data for a single mesh */
  struct Mesh
  {
      Mesh()
      {
          for (unsigned int i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS;++i)
              mNumUVComponents[i] = 2;
      }
  
      std::string mName;
  
      // just to check if there's some sophisticated addressing involved...
      // which we don't support, and therefore should warn about.
      std::string mVertexID;
  
      // Vertex data addressed by vertex indices
      std::vector<InputChannel> mPerVertexData;
  
      // actual mesh data, assembled on encounter of a <p> element. Verbose format, not indexed
      std::vector<aiVector3D> mPositions;
      std::vector<aiVector3D> mNormals;
      std::vector<aiVector3D> mTangents;
      std::vector<aiVector3D> mBitangents;
      std::vector<aiVector3D> mTexCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS];
      std::vector<aiColor4D>  mColors[AI_MAX_NUMBER_OF_COLOR_SETS];
  
      unsigned int mNumUVComponents[AI_MAX_NUMBER_OF_TEXTURECOORDS];
  
      // Faces. Stored are only the number of vertices for each face.
      // 1 == point, 2 == line, 3 == triangle, 4+ == poly
      std::vector<size_t> mFaceSize;
  
      // Position indices for all faces in the sequence given in mFaceSize -
      // necessary for bone weight assignment
      std::vector<size_t> mFacePosIndices;
  
      // Submeshes in this mesh, each with a given material
      std::vector<SubMesh> mSubMeshes;
  };
  
  /** Which type of primitives the ReadPrimitives() function is going to read */
  enum PrimitiveType
  {
      Prim_Invalid,
      Prim_Lines,
      Prim_LineStrip,
      Prim_Triangles,
      Prim_TriStrips,
      Prim_TriFans,
      Prim_Polylist,
      Prim_Polygon
  };
  
  /** A skeleton controller to deform a mesh with the use of joints */
  struct Controller
  {
      // controller type
      ControllerType mType;
  
      // Morphing method if type is Morph
      MorphMethod mMethod;
  
      // the URL of the mesh deformed by the controller.
      std::string mMeshId;
  
      // accessor URL of the joint names
      std::string mJointNameSource;
  
      ///< The bind shape matrix, as array of floats. I'm not sure what this matrix actually describes, but it can't be ignored in all cases
      ai_real mBindShapeMatrix[16];
  
      // accessor URL of the joint inverse bind matrices
      std::string mJointOffsetMatrixSource;
  
      // input channel: joint names.
      InputChannel mWeightInputJoints;
      // input channel: joint weights
      InputChannel mWeightInputWeights;
  
      // Number of weights per vertex.
      std::vector<size_t> mWeightCounts;
  
      // JointIndex-WeightIndex pairs for all vertices
      std::vector< std::pair<size_t, size_t> > mWeights;
  
      std::string mMorphTarget;
      std::string mMorphWeight;
  };
  
  /** A collada material. Pretty much the only member is a reference to an effect. */
  struct Material
  {
      std::string mName;
      std::string mEffect;
  };
  
  /** Type of the effect param */
  enum ParamType
  {
      Param_Sampler,
      Param_Surface
  };
  
  /** A param for an effect. Might be of several types, but they all just refer to each other, so I summarize them */
  struct EffectParam
  {
      ParamType mType;
      std::string mReference; // to which other thing the param is referring to.
  };
  
  /** Shading type supported by the standard effect spec of Collada */
  enum ShadeType
  {
      Shade_Invalid,
      Shade_Constant,
      Shade_Lambert,
      Shade_Phong,
      Shade_Blinn
  };
  
  /** Represents a texture sampler in collada */
  struct Sampler
  {
      Sampler()
          :   mWrapU      (true)
          ,   mWrapV      (true)
          ,   mMirrorU    ()
          ,   mMirrorV    ()
          ,   mOp         (aiTextureOp_Multiply)
          ,   mUVId       (UINT_MAX)
          ,   mWeighting  (1.f)
          ,   mMixWithPrevious (1.f)
      {}
  
      /** Name of image reference
       */
      std::string mName;
  
      /** Wrap U?
       */
      bool mWrapU;
  
      /** Wrap V?
       */
      bool mWrapV;
  
      /** Mirror U?
       */
      bool mMirrorU;
  
      /** Mirror V?
       */
      bool mMirrorV;
  
      /** Blend mode
       */
      aiTextureOp mOp;
  
      /** UV transformation
       */
      aiUVTransform mTransform;
  
      /** Name of source UV channel
       */
      std::string mUVChannel;
  
      /** Resolved UV channel index or UINT_MAX if not known
       */
      unsigned int mUVId;
  
      // OKINO/MAX3D extensions from here
      // -------------------------------------------------------
  
      /** Weighting factor
       */
      ai_real mWeighting;
  
      /** Mixing factor from OKINO
       */
      ai_real mMixWithPrevious;
  };
  
  /** A collada effect. Can contain about anything according to the Collada spec,
      but we limit our version to a reasonable subset. */
  struct Effect
  {
      // Shading mode
      ShadeType mShadeType;
  
      // Colors
      aiColor4D mEmissive, mAmbient, mDiffuse, mSpecular,
          mTransparent, mReflective;
  
      // Textures
      Sampler mTexEmissive, mTexAmbient, mTexDiffuse, mTexSpecular,
          mTexTransparent, mTexBump, mTexReflective;
  
      // Scalar factory
      ai_real mShininess, mRefractIndex, mReflectivity;
      ai_real mTransparency;
      bool mHasTransparency;
      bool mRGBTransparency;
      bool mInvertTransparency;
  
      // local params referring to each other by their SID
      typedef std::map<std::string, Collada::EffectParam> ParamLibrary;
      ParamLibrary mParams;
  
      // MAX3D extensions
      // ---------------------------------------------------------
      // Double-sided?
      bool mDoubleSided, mWireframe, mFaceted;
  
      Effect()
          : mShadeType    (Shade_Phong)
          , mEmissive     ( 0, 0, 0, 1)
          , mAmbient      ( 0.1f, 0.1f, 0.1f, 1)
          , mDiffuse      ( 0.6f, 0.6f, 0.6f, 1)
          , mSpecular     ( 0.4f, 0.4f, 0.4f, 1)
          , mTransparent  ( 0, 0, 0, 1)
          , mShininess    (10.0f)
          , mRefractIndex (1.f)
          , mReflectivity (0.f)
          , mTransparency (1.f)
          , mHasTransparency (false)
          , mRGBTransparency(false)
          , mInvertTransparency(false)
          , mDoubleSided  (false)
          , mWireframe    (false)
          , mFaceted      (false)
      {
      }
  };
  
  /** An image, meaning texture */
  struct Image
  {
      std::string mFileName;
  
      /** Embedded image data */
      std::vector<uint8_t> mImageData;
  
      /** File format hint ofembedded image data */
      std::string mEmbeddedFormat;
  };
  
  /** An animation channel. */
  struct AnimationChannel
  {
      /** URL of the data to animate. Could be about anything, but we support only the
       * "NodeID/TransformID.SubElement" notation
       */
      std::string mTarget;
  
      /** Source URL of the time values. Collada calls them "input". Meh. */
      std::string mSourceTimes;
      /** Source URL of the value values. Collada calls them "output". */
      std::string mSourceValues;
      /** Source URL of the IN_TANGENT semantic values. */
      std::string mInTanValues;
      /** Source URL of the OUT_TANGENT semantic values. */
      std::string mOutTanValues;
      /** Source URL of the INTERPOLATION semantic values. */
      std::string mInterpolationValues;
  };
  
  /** An animation. Container for 0-x animation channels or 0-x animations */
  struct Animation
  {
      /** Anim name */
      std::string mName;
  
      /** the animation channels, if any */
      std::vector<AnimationChannel> mChannels;
  
      /** the sub-animations, if any */
      std::vector<Animation*> mSubAnims;
  
      /** Destructor */
      ~Animation()
      {
          for( std::vector<Animation*>::iterator it = mSubAnims.begin(); it != mSubAnims.end(); ++it)
              delete *it;
      }
  
  	/** Collect all channels in the animation hierarchy into a single channel list. */
  	void CollectChannelsRecursively(std::vector<AnimationChannel> &channels)
  	{
  		channels.insert(channels.end(), mChannels.begin(), mChannels.end());
  
  		for (std::vector<Animation*>::iterator it = mSubAnims.begin(); it != mSubAnims.end(); ++it)
  		{
  			Animation *pAnim = (*it);
  
  			pAnim->CollectChannelsRecursively(channels);
  		}
  	}
  
  	/** Combine all single-channel animations' channel into the same (parent) animation channel list. */
  	void CombineSingleChannelAnimations()
  	{
  		CombineSingleChannelAnimationsRecursively(this);
  	}
  
  	void CombineSingleChannelAnimationsRecursively(Animation *pParent)
  	{
  		for (std::vector<Animation*>::iterator it = pParent->mSubAnims.begin(); it != pParent->mSubAnims.end();)
  		{
  			Animation *anim = *it;
  
  			CombineSingleChannelAnimationsRecursively(anim);
  
  			if (anim->mChannels.size() == 1)
  			{
  				pParent->mChannels.push_back(anim->mChannels[0]);
  
  				it = pParent->mSubAnims.erase(it);
  
  				delete anim;
  			}
  			else
  			{
  				++it;
  			}
  		}
  	}
  };
  
  /** Description of a collada animation channel which has been determined to affect the current node */
  struct ChannelEntry
  {
      const Collada::AnimationChannel* mChannel; ///> the source channel
      std::string mTargetId;
      std::string mTransformId;   // the ID of the transformation step of the node which is influenced
      size_t mTransformIndex; // Index into the node's transform chain to apply the channel to
      size_t mSubElement; // starting index inside the transform data
  
      // resolved data references
      const Collada::Accessor* mTimeAccessor; ///> Collada accessor to the time values
      const Collada::Data* mTimeData; ///> Source data array for the time values
      const Collada::Accessor* mValueAccessor; ///> Collada accessor to the key value values
      const Collada::Data* mValueData; ///> Source datat array for the key value values
  
      ChannelEntry()
        : mChannel()
        , mTransformIndex()
        , mSubElement()
        , mTimeAccessor()
        , mTimeData()
        , mValueAccessor()
        , mValueData()
     {}
  };
  
  } // end of namespace Collada
  } // end of namespace Assimp
  
  #endif // AI_COLLADAHELPER_H_INC
  