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/**
 * Definitions for import post processing steps.
 */
module assimp.postprocess;

extern ( C ) {
   /**
    * Defines the flags for all possible post processing steps.
    *
    * See: <code>aiImportFile</code>, <code>aiImportFileEx</code>
    */
   enum aiPostProcessSteps {
      /**
       * Calculates the tangents and bitangents for the imported meshes.
       *
       * Does nothing if a mesh does not have normals. You might want this post
       * processing step to be executed if you plan to use tangent space
       * calculations such as normal mapping applied to the meshes. There is a
       * config setting, <code>AI_CONFIG_PP_CT_MAX_SMOOTHING_ANGLE</code>,
       * which allows you to specify a maximum smoothing angle for the
       * algorithm. However, usually you will want to use the default value.
       */
      CalcTangentSpace = 0x1,

      /**
       * Identifies and joins identical vertex data sets within all imported
       * meshes.
       *
       * After this step is run each mesh does contain only unique vertices
       * anymore, so a vertex is possibly used by multiple faces. You usually
       * want to use this post processing step. If your application deals with
       * indexed geometry, this step is compulsory or you will just waste
       * rendering time. <em>If this flag is not specified</em>, no vertices
       * are referenced by more than one face and <em>no index buffer is
       * required</em> for rendering.
       */
      JoinIdenticalVertices = 0x2,

      /**
       * Converts all the imported data to a left-handed coordinate space.
       *
       * By default the data is returned in a right-handed coordinate space
       * which for example OpenGL prefers. In this space, +X points to the
       * right, +Z points towards the viewer and and +Y points upwards. In the
       * DirectX coordinate space +X points to the right, +Y points upwards and
       * +Z points away from the viewer.
       *
       * You will probably want to consider this flag if you use Direct3D for
       * rendering. The <code>ConvertToLeftHanded</code> flag supersedes this
       * setting and bundles all conversions typically required for D3D-based
       * applications.
       */
      MakeLeftHanded = 0x4,

      /**
       * Triangulates all faces of all meshes.
       *
       * By default the imported mesh data might contain faces with more than 3
       * indices. For rendering you'll usually want all faces to be triangles.
       * This post processing step splits up all higher faces to triangles.
       * Line and point primitives are <em>not</em> modified!.
       *
       * If you want »triangles only« with no other kinds of primitives,
       * specify both <code>Triangulate</code> and <code>SortByPType</code> and
       * ignore all point and line meshes when you process Assimp's output.
       */
      Triangulate = 0x8,

      /**
       * Removes some parts of the data structure (animations, materials, light
       * sources, cameras, textures, vertex components).
       *
       * The components to be removed are specified in a separate configuration
       * option, <code>AI_CONFIG_PP_RVC_FLAGS</code>. This is quite useful if
       * you don't need all parts of the output structure. Especially vertex
       * colors are rarely used today.
       *
       * Calling this step to remove unrequired stuff from the pipeline as
       * early as possible results in an increased performance and a better
       * optimized output data structure.
       *
       * This step is also useful if you want to force Assimp to recompute
       * normals or tangents since the corresponding steps don't recompute them
       * if they have already been loaded from the source asset.
       *
       * This flag is a poor one, mainly because its purpose is usually
       * misunderstood. Consider the following case: a 3d model has been exported
       * from a CAD app, it has per-face vertex colors. Because of the vertex
       * colors (which are not even used by most apps),
       * <code>JoinIdenticalVertices</code> cannot join vertices at the same
       * position. By using this step, unneeded components are excluded as
       * early as possible thus opening more room for internal optimzations.
       */
      RemoveComponent = 0x10,

      /**
       * Generates normals for all faces of all meshes.
       *
       * This is ignored if normals are already there at the time where this
       * flag is evaluated. Model importers try to load them from the source
       * file, so they are usually already there. Face normals are shared
       * between all points of a single face, so a single point can have
       * multiple normals, which, in other words, enforces the library to
       * duplicate vertices in some cases. <code>JoinIdenticalVertices</code>
       * is <em>useless</em> then.
       *
       * This flag may not be specified together with
       * <code>GenSmoothNormals</code>.
       */
      GenNormals = 0x20,

      /**
       * Generates smooth normals for all vertices in the mesh.
       *
       * This is ignored if normals are already there at the time where this
       * flag is evaluated. Model importers try to load them from the source file, so
       * they are usually already there.
       *
       * There is a configuration option,
       * <code>AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE</code> which allows you to
       * specify an angle maximum for the normal smoothing algorithm. Normals
       * exceeding this limit are not smoothed, resulting in a »hard« seam
       * between two faces. Using a decent angle here (e.g. 80°) results in
       * very good visual appearance.
       */
      GenSmoothNormals = 0x40,

      /**
       * Splits large meshes into smaller submeshes.
       *
       * This is quite useful for realtime rendering where the number of triangles
       * which can be maximally processed in a single draw-call is usually limited
       * by the video driver/hardware. The maximum vertex buffer is usually limited,
       * too. Both requirements can be met with this step: you may specify both a
       * triangle and vertex limit for a single mesh.
       *
       * The split limits can (and should!) be set through the
       * <code>AI_CONFIG_PP_SLM_VERTEX_LIMIT</code> and
       * <code>AI_CONFIG_PP_SLM_TRIANGLE_LIMIT</code> settings. The default
       * values are <code>AI_SLM_DEFAULT_MAX_VERTICES</code> and
       * <code>AI_SLM_DEFAULT_MAX_TRIANGLES</code>.
       *
       * Note that splitting is generally a time-consuming task, but not if
       * there's nothing to split. The use of this step is recommended for most
       * users.
       */
      SplitLargeMeshes = 0x80,

      /**
       * Removes the node graph and pre-transforms all vertices with the local
       * transformation matrices of their nodes.
       *
       * The output scene does still contain nodes, however, there is only a
       * root node with children, each one referencing only one mesh, each
       * mesh referencing one material. For rendering, you can simply render
       * all meshes in order, you don't need to pay attention to local
       * transformations and the node hierarchy. Animations are removed during
       * this step.
       *
       * This step is intended for applications that have no scenegraph.
       *
       * The step <em>can</em> cause some problems: if e.g. a mesh of the asset
       * contains normals and another, using the same material index, does not,
       * they will be brought together, but the first meshes's part of the
       * normal list is zeroed. However, these artifacts are rare.
       *
       * Note: The <code>AI_CONFIG_PP_PTV_NORMALIZE</code> configuration
       *    property can be set to normalize the scene's spatial dimension
       *    to the -1...1 range.
       */
      PreTransformVertices = 0x100,

      /**
       * Limits the number of bones simultaneously affecting a single vertex to
       * a maximum value.
       *
       * If any vertex is affected by more than that number of bones, the least
       * important vertex weights are removed and the remaining vertex weights
       * are renormalized so that the weights still sum up to 1.
       *
       * The default bone weight limit is 4 (<code>AI_LMW_MAX_WEIGHTS</code>),
       * but you can use the <code>#AI_CONFIG_PP_LBW_MAX_WEIGHTS</code> setting
       * to supply your own limit to the post processing step.
       *
       * If you intend to perform the skinning in hardware, this post processing
       * step might be of interest for you.
       */
      LimitBoneWeights = 0x200,

      /**
       * Validates the imported scene data structure.
       *
       * This makes sure that all indices are valid, all animations and
       * bones are linked correctly, all material references are correct, etc.
       *
       * It is recommended to capture Assimp's log output if you use this flag,
       * so you can easily find ot what's actually wrong if a file fails the
       * validation. The validator is quite rude and will find <em>all</em>
       * inconsistencies in the data structure.
       *
       * Plugin developers are recommended to use it to debug their loaders.
       *
       * There are two types of validation failures:
       * <ul>
       * <li>Error: There's something wrong with the imported data. Further
       *    postprocessing is not possible and the data is not usable at all.
       *    The import fails, see <code>aiGetErrorString()</code> for the
       *    error message.</li>
       * <li>Warning: There are some minor issues (e.g. 1000000 animation
       *   keyframes with the same time), but further postprocessing and use
       *   of the data structure is still safe. Warning details are written
       *   to the log file, <code>AI_SCENE_FLAGS_VALIDATION_WARNING</code> is
       *   set in <code>aiScene::mFlags</code></li>
       * </ul>
       *
       * This post-processing step is not time-consuming. It's use is not
       * compulsory, but recommended.
       */
      ValidateDataStructure = 0x400,

      /**
       * Reorders triangles for better vertex cache locality.
       *
       * The step tries to improve the ACMR (average post-transform vertex cache
       * miss ratio) for all meshes. The implementation runs in O(n) and is
       * roughly based on the 'tipsify' algorithm (see
       * <tt>http://www.cs.princeton.edu/gfx/pubs/Sander_2007_%3ETR/tipsy.pdf</tt>).
       *
       * If you intend to render huge models in hardware, this step might
       * be of interest for you. The <code>AI_CONFIG_PP_ICL_PTCACHE_SIZE</code>
       * config setting can be used to fine-tune the cache optimization.
       */
      ImproveCacheLocality = 0x800,

      /**
       * Searches for redundant/unreferenced materials and removes them.
       *
       * This is especially useful in combination with the
       * <code>PretransformVertices</code> and <code>OptimizeMeshes</code>
       * flags. Both join small meshes with equal characteristics, but they
       * can't do their work if two meshes have different materials. Because
       * several material settings are always lost during Assimp's import
       * filters, (and because many exporters don't check for redundant
       * materials), huge models often have materials which are are defined
       * several times with exactly the same settings.
       *
       * Several material settings not contributing to the final appearance of
       * a surface are ignored in all comparisons; the material name is one of
       * them. So, if you are passing additional information through the
       * content pipeline (probably using »magic« material names), don't
       * specify this flag. Alternatively take a look at the
       * <code>AI_CONFIG_PP_RRM_EXCLUDE_LIST</code> setting.
       */
      RemoveRedundantMaterials = 0x1000,

      /**
       * This step tries to determine which meshes have normal vectors that are
       * acing inwards.
       *
       * The algorithm is simple but effective: The bounding box of all
       * vertices and their normals is compared against the volume of the
       * bounding box of all vertices without their normals. This works well
       * for most objects, problems might occur with planar surfaces. However,
       * the step tries to filter such cases.
       *
       * The step inverts all in-facing normals. Generally it is recommended to
       * enable this step, although the result is not always correct.
       */
      FixInfacingNormals = 0x2000,

      /**
       * This step splits meshes with more than one primitive type in
       * homogeneous submeshes.
       *
       * The step is executed after the triangulation step. After the step
       * returns, just one bit is set in <code>aiMesh.mPrimitiveTypes</code>.
       * This is especially useful for real-time rendering where point and line
       * primitives are often ignored or rendered separately.
       *
       * You can use the <code>AI_CONFIG_PP_SBP_REMOVE</code> option to
       * specify which primitive types you need. This can be used to easily
       * exclude lines and points, which are rarely used, from the import.
       */
      SortByPType = 0x8000,

      /**
       * This step searches all meshes for degenerated primitives and converts
       * them to proper lines or points.
       *
       * A face is »degenerated« if one or more of its points are identical.
       * To have the degenerated stuff not only detected and collapsed but also
       * removed, try one of the following procedures:
       *
       * <b>1.</b> (if you support lines and points for rendering but don't
       *    want the degenerates)
       * <ul>
       *   <li>Specify the <code>FindDegenerates</code> flag.</li>
       *   <li>Set the <code>AI_CONFIG_PP_FD_REMOVE</code> option to 1. This will
       *       cause the step to remove degenerated triangles from the import
       *       as soon as they're detected. They won't pass any further
       *       pipeline steps.</li>
       * </ul>
       *
       * <b>2.</b>(if you don't support lines and points at all ...)
       * <ul>
       *   <li>Specify the <code>FindDegenerates</code> flag.</li>
       *   <li>Specify the <code>SortByPType</code> flag. This moves line and
       *      point primitives to separate meshes.</li>
       *   <li>Set the <code>AI_CONFIG_PP_SBP_REMOVE</codet> option to
       *      <code>aiPrimitiveType_POINTS | aiPrimitiveType_LINES</code>
       *      to cause SortByPType to reject point and line meshes from the
       *      scene.</li>
       * </ul>
       *
       * Note: Degenerated polygons are not necessarily bad and that's why
       *    they're not removed by default. There are several file formats
       *    which don't support lines or points. Some exporters bypass the
       *    format specification and write them as degenerated triangle
       *    instead.
       */
      FindDegenerates = 0x10000,

      /**
       * This step searches all meshes for invalid data, such as zeroed normal
       * vectors or invalid UV coords and removes/fixes them. This is intended
       * to get rid of some common exporter errors.
       *
       * This is especially useful for normals. If they are invalid, and the
       * step recognizes this, they will be removed and can later be
       * recomputed, e.g. by the <code>GenSmoothNormals</code> step.
       *
       * The step will also remove meshes that are infinitely small and reduce
       * animation tracks consisting of hundreds if redundant keys to a single
       * key. The <code>AI_CONFIG_PP_FID_ANIM_ACCURACY</code> config property
       * decides the accuracy of the check for duplicate animation tracks.
       */
      FindInvalidData = 0x20000,

      /**
       * This step converts non-UV mappings (such as spherical or cylindrical
       * mapping) to proper texture coordinate channels.
       *
       * Most applications will support UV mapping only, so you will probably
       * want to specify this step in every case. Note tha Assimp is not always
       * able to match the original mapping implementation of the 3d app which
       * produced a model perfectly. It's always better to let the father app
       * compute the UV channels, at least 3ds max, maja, blender, lightwave,
       * modo, ... are able to achieve this.
       *
       * Note: If this step is not requested, you'll need to process the
       *    <code>AI_MATKEY_MAPPING</code> material property in order to
       *    display all assets properly.
       */
      GenUVCoords = 0x40000,

      /**
       * This step applies per-texture UV transformations and bakes them to
       * stand-alone vtexture coordinate channelss.
       *
       * UV transformations are specified per-texture – see the
       * <code>AI_MATKEY_UVTRANSFORM</code> material key for more information.
       * This step processes all textures with transformed input UV coordinates
       * and generates new (pretransformed) UV channel which replace the old
       * channel. Most applications won't support UV transformations, so you
       * will probably want to specify this step.
       *
       * Note: UV transformations are usually implemented in realtime apps by
       *    transforming texture coordinates at vertex shader stage with a 3x3
       *    (homogenous) transformation matrix.
       */
      TransformUVCoords = 0x80000,

      /**
       * This step searches for duplicate meshes and replaces duplicates with
       * references to the first mesh.
       *
       * This step takes a while, don't use it if you have no time. Its main
       * purpose is to workaround the limitation that many export file formats
       * don't support instanced meshes, so exporters need to duplicate meshes.
       * This step removes the duplicates again. Please note that Assimp does
       * currently not support per-node material assignment to meshes, which
       * means that identical meshes with differnent materials are currently
       * <em>not</em> joined, although this is planned for future versions.
       */
      FindInstances = 0x100000,

      /**
       * A postprocessing step to reduce the number of meshes.
       *
       * In fact, it will reduce the number of drawcalls.
       *
       * This is a very effective optimization and is recommended to be used
       * together with <code>OptimizeGraph</code>, if possible. The flag is
       * fully compatible with both <code>SplitLargeMeshes</code> and
       * <code>SortByPType</code>.
       */
      OptimizeMeshes = 0x200000,

      /**
       * A postprocessing step to optimize the scene hierarchy.
       *
       * Nodes with no animations, bones, lights or cameras assigned are
       * collapsed and joined.
       *
       * Node names can be lost during this step. If you use special tag nodes
       * to pass additional information through your content pipeline, use the
       * <code>AI_CONFIG_PP_OG_EXCLUDE_LIST</code> setting to specify a list of
       * node names you want to be kept. Nodes matching one of the names in
       * this list won't be touched or modified.
       *
       * Use this flag with caution. Most simple files will be collapsed to a
       * single node, complex hierarchies are usually completely lost. That's
       * note the right choice for editor environments, but probably a very
       * effective optimization if you just want to get the model data, convert
       * it to your own format and render it as fast as possible.
       *
       * This flag is designed to be used with <code>OptimizeMeshes</code> for
       * best results.
       *
       * Note: »Crappy« scenes with thousands of extremely small meshes packed
       *    in deeply nested nodes exist for almost all file formats.
       *    <code>OptimizeMeshes</code> in combination with
       *    <code>OptimizeGraph</code> usually fixes them all and makes them
       *    renderable.
       */
      OptimizeGraph  = 0x400000,

      /** This step flips all UV coordinates along the y-axis and adjusts
       * material settings and bitangents accordingly.
       *
       * Output UV coordinate system:
       * <pre> 0y|0y ---------- 1x|0y
       * |                 |
       * |                 |
       * |                 |
       * 0x|1y ---------- 1x|1y</pre>
       * You'll probably want to consider this flag if you use Direct3D for
       * rendering. The <code>AI_PROCESS_CONVERT_TO_LEFT_HANDED</code> flag
       * supersedes this setting and bundles all conversions typically required
       * for D3D-based applications.
      */
      FlipUVs = 0x800000,

      /**
       * This step adjusts the output face winding order to be clockwise.
       *
       * The default face winding order is counter clockwise.
       *
       * Output face order:
       * <pre>       x2
       *
       *                         x0
       *  x1</pre>
       */
      FlipWindingOrder  = 0x1000000
   }

   /**
    * Abbrevation for convenience.
    */
   alias aiPostProcessSteps aiProcess;

   /**
    * Shortcut flag for Direct3D-based applications.
    *
    * Combines the <code>MakeLeftHanded</code>, <code>FlipUVs</code> and
    * <code>FlipWindingOrder</code> flags. The output data matches Direct3D's
    * conventions: left-handed geometry, upper-left origin for UV coordinates
    * and clockwise face order, suitable for CCW culling.
    */
   const aiPostProcessSteps AI_PROCESS_CONVERT_TO_LEFT_HANDED =
      aiProcess.MakeLeftHanded |
      aiProcess.FlipUVs |
      aiProcess.FlipWindingOrder;

   /**
    * Default postprocess configuration optimizing the data for real-time rendering.
    *
    * Applications would want to use this preset to load models on end-user
    * PCs, maybe for direct use in game.
    *
    * If you're using DirectX, don't forget to combine this value with
    * the <code>ConvertToLeftHanded</code> step. If you don't support UV
    * transformations in your application, apply the
    * <code>TransformUVCoords</code> step, too.
    *
    * Note: Please take the time to read the doc for the steps enabled by this
    *   preset. Some of them offer further configurable properties, some of
    *   them might not be of use for you so it might be better to not specify
    *   them.
    */
   const aiPostProcessSteps AI_PROCESS_PRESET_TARGET_REALTIME_FAST =
      aiProcess.CalcTangentSpace |
      aiProcess.GenNormals |
      aiProcess.JoinIdenticalVertices |
      aiProcess.Triangulate |
      aiProcess.GenUVCoords |
      aiProcess.SortByPType;

    /**
     * Default postprocess configuration optimizing the data for real-time
     * rendering.
     *
     * Unlike <code>AI_PROCESS_PRESET_TARGET_REALTIME_FAST</code>, this
     * configuration performs some extra optimizations to improve rendering
     * speed and to minimize memory usage. It could be a good choice for a
     * level editor environment where import speed is not so important.
     *
     * If you're using DirectX, don't forget to combine this value with
     * the <code>ConvertToLeftHanded</code> step. If you don't support UV
     * transformations in your application, apply the
     * <code>TransformUVCoords</code> step, too.
     *
     * Note: Please take the time to read the doc for the steps enabled by this
     *   preset. Some of them offer further configurable properties, some of
     *   them might not be of use for you so it might be better to not specify
     *   them.
     */
   const aiPostProcessSteps AI_PROCESS_PRESET_TARGET_REALTIME_QUALITY =
      aiProcess.CalcTangentSpace |
      aiProcess.GenSmoothNormals |
      aiProcess.JoinIdenticalVertices |
      aiProcess.ImproveCacheLocality |
      aiProcess.LimitBoneWeights |
      aiProcess.RemoveRedundantMaterials |
      aiProcess.SplitLargeMeshes |
      aiProcess.Triangulate |
      aiProcess.GenUVCoords |
      aiProcess.SortByPType |
      aiProcess.FindDegenerates |
      aiProcess.FindInvalidData;

    /**
     * Default postprocess configuration optimizing the data for real-time
     * rendering.
     *
     * This preset enables almost every optimization step to achieve perfectly
     * optimized data. It's your choice for level editor environments where
     * import speed is not important.
     *
     * If you're using DirectX, don't forget to combine this value with
     * the <code>ConvertToLeftHanded</code> step. If you don't support UV
     * transformations in your application, apply the
     * <code>TransformUVCoords</code> step, too.
     *
     * Note: Please take the time to read the doc for the steps enabled by this
     *   preset. Some of them offer further configurable properties, some of
     *   them might not be of use for you so it might be better to not specify
     *   them.
     */
   const aiPostProcessSteps AI_PROCESS_PRESET_TARGET_REALTIME_MAX_QUALITY =
      AI_PROCESS_PRESET_TARGET_REALTIME_QUALITY |
      aiProcess.FindInstances |
      aiProcess.ValidateDataStructure |
      aiProcess.OptimizeMeshes;
}
