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Open Asset Import Library (ASSIMP)
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*/

/**
 * Contains the material system which stores the imported material information.
 */
module assimp.material;

import assimp.math;
import assimp.types;

extern ( C ) {
   /**
    * Default material names for meshes without UV coordinates.
    */
   const char* AI_DEFAULT_MATERIAL_NAME = "aiDefaultMat";

   /**
    * Default material names for meshes with UV coordinates.
    */
   const char* AI_DEFAULT_TEXTURED_MATERIAL_NAME = "TexturedDefaultMaterial";

   /**
    * Defines how the Nth texture of a specific type is combined with the
    * result of all previous layers.
    *
    * Example (left: key, right: value):
    * <pre> DiffColor0     - gray
    * DiffTextureOp0 - aiTextureOpMultiply
    * DiffTexture0   - tex1.png
    * DiffTextureOp0 - aiTextureOpAdd
    * DiffTexture1   - tex2.png</pre>
    * Written as equation, the final diffuse term for a specific pixel would be:
    * <pre>diffFinal = DiffColor0 * sampleTex( DiffTexture0, UV0 ) +
    *     sampleTex( DiffTexture1, UV0 ) * diffContrib;</pre>
    * where <code>diffContrib</code> is the intensity of the incoming light for
    * that pixel.
    */
   enum aiTextureOp : uint {
      /**
       * <code>T = T1 * T2</code>
       */
      Multiply = 0x0,

      /**
       * <code>T = T1 + T2</code>
       */
      Add = 0x1,

      /**
       * <code>T = T1 - T2</code>
       */
      Subtract = 0x2,

      /**
       * <code>T = T1 / T2</code>
       */
      Divide = 0x3,

      /**
       * <code>T = ( T1 + T2 ) - ( T1 * T2 )</code>
       */
      SmoothAdd = 0x4,

      /**
       * <code>T = T1 + ( T2 - 0.5 )</code>
       */
      SignedAdd = 0x5
   }

   /**
    * Defines how UV coordinates outside the <code>[0..1]</code> range are
    * handled.
    *
    * Commonly referred to as 'wrapping mode'.
    */
   enum aiTextureMapMode : uint {
      /**
       * A texture coordinate <code>u | v</code> is translated to
       * <code>(u%1) | (v%1)</code>.
       */
      Wrap = 0x0,

      /**
       * Texture coordinates are clamped to the nearest valid value.
       */
      Clamp = 0x1,

      /**
       * If the texture coordinates for a pixel are outside
       * <code>[0..1]</code>, the texture is not applied to that pixel.
       */
      Decal = 0x3,

      /**
       * A texture coordinate <code>u | v</code> becomes
       * <code>(u%1) | (v%1)</code> if <code>(u-(u%1))%2</code> is
       * zero and <code>(1-(u%1)) | (1-(v%1))</code> otherwise.
       */
      Mirror = 0x2
   }

   /**
    * Defines how the mapping coords for a texture are generated.
    *
    * Real-time applications typically require full UV coordinates, so the use of
    * the <code>aiProcess.GenUVCoords</code> step is highly recommended. It
    * generates proper UV channels for non-UV mapped objects, as long as an
    * accurate description how the mapping should look like (e.g spherical) is
    * given. See the <code>AI_MATKEY_MAPPING</code> property for more details.
    */
   enum aiTextureMapping : uint {
      /**
       * The mapping coordinates are taken from an UV channel.
       *
       * The <code>AI_MATKEY_UVSRC</code> key specifies from which (remember,
       * meshes can have more than one UV channel).
       */
      UV = 0x0,

      /**
       * Spherical mapping.
       */
      SPHERE = 0x1,

      /**
       * Cylindrical mapping.
       */
      CYLINDER = 0x2,

      /**
       * Cubic mapping.
       */
      BOX = 0x3,

      /**
       * Planar mapping.
       */
      PLANE = 0x4,

      /**
       * Undefined mapping.
       */
      OTHER = 0x5
   }

   /**
    * Defines the purpose of a texture
    *
    * This is a very difficult topic. Different 3D packages support different
    * kinds of textures. For very common texture types, such as bumpmaps, the
    * rendering results depend on implementation details in the rendering
    * pipelines of these applications. Assimp loads all texture references from
    * the model file and tries to determine which of the predefined texture
    * types below is the best choice to match the original use of the texture
    * as closely as possible.
    *
    * In content pipelines you'll usually define how textures have to be
    * handled, and the artists working on models have to conform to this
    * specification, regardless which 3D tool they're using.
    */
   enum aiTextureType : uint {
      /**
       * No texture, but the value to be used for
       * <code>aiMaterialProperty.mSemantic</code> for all material properties
       * <em>not</em> related to textures.
       */
      NONE = 0x0,

      /**
       * The texture is combined with the result of the diffuse lighting
       * equation.
       */
      DIFFUSE = 0x1,

      /**
       * The texture is combined with the result of the specular lighting
       * equation.
       */
      SPECULAR = 0x2,

      /**
       * The texture is combined with the result of the ambient lighting
       * equation.
       */
      AMBIENT = 0x3,

      /**
       * The texture is added to the result of the lighting calculation. It
       * isn't influenced by incoming light.
       */
      EMISSIVE = 0x4,

      /**
       * The texture is a height map.
       *
       * By convention, higher grey-scale values stand for higher elevations
       * from the base height.
       */
      HEIGHT = 0x5,

      /**
       * The texture is a (tangent space) normal-map.
       *
       * Again, there are several conventions for tangent-space normal maps.
       * Assimp does (intentionally) not differenciate here.
       */
      NORMALS = 0x6,

      /**
       * The texture defines the glossiness of the material.
       *
       * The glossiness is in fact the exponent of the specular (phong)
       * lighting equation. Usually there is a conversion function defined to
       * map the linear color values in the texture to a suitable exponent.
       */
      SHININESS = 0x7,

      /**
       * The texture defines per-pixel opacity.
       *
       * Usually white means opaque and black means transparent.
       */
      OPACITY = 0x8,

      /**
       * Displacement texture.
       *
       * The exact purpose and format is application-dependent. Higher color
       * values stand for higher vertex displacements.
       */
      DISPLACEMENT = 0x9,

      /**
       * Lightmap or ambient occlusion texture.
       *
       * Both lightmaps and dedicated ambient occlusion maps are covered by
       * this material property. The texture contains a scaling value for the
       * final color value of a pixel. Its intensity is not affected by
       * incoming light.
       */
      LIGHTMAP = 0xA,

      /**
       * Reflection texture.
       *
       * Contains the color of a perfect mirror reflection. Rarely used, almost
       * never for real-time applications.
       */
      REFLECTION = 0xB,

      /**
       * Unknown texture.
       *
       * A texture reference that does not match any of the definitions above is
       * considered to be 'unknown'. It is still imported, but is excluded from
       * any further postprocessing.
       */
      UNKNOWN = 0xC
   }

   /**
    * Defines all shading models supported by the library
    *
    * The list of shading modes has been taken from Blender. See Blender
    * documentation for more information. The API does not distinguish between
    * "specular" and "diffuse" shaders (thus the specular term for diffuse
    * shading models like Oren-Nayar remains undefined).
    *
    * Again, this value is just a hint. Assimp tries to select the shader whose
    * most common implementation matches the original rendering results of the
    * 3D modeller which wrote a particular model as closely as possible.
    */
   enum aiShadingMode : uint {
      /**
       * Flat shading.
       *
       * Shading is done on per-face base diffuse only. Also known as
       * »faceted shading«.
       */
      Flat = 0x1,

      /**
       * Simple Gouraud shading.
       */
      Gouraud =   0x2,

      /**
       * Phong-Shading.
       */
      Phong = 0x3,

      /**
       * Phong-Blinn-Shading.
       */
      Blinn = 0x4,

      /**
       * Per-pixel toon shading.
       *
       * Often referred to as »comic shading«.
       */
      Toon = 0x5,

      /**
       * Per-pixel Oren-Nayar shading.
       *
       * Extension to standard Lambertian shading, taking the roughness of the
       * material into account.
       */
      OrenNayar = 0x6,

      /**
       * Per-pixel Minnaert shading.
       *
       * Extension to standard Lambertian shading, taking the "darkness" of the
       * material into account.
       */
      Minnaert = 0x7,

      /**
       * Per-pixel Cook-Torrance shading.
       *
       * Special shader for metallic surfaces.
       */
      CookTorrance = 0x8,

      /**
       * No shading at all.
       *
       * Constant light influence of 1.
       */
      NoShading = 0x9,

      /**
       * Fresnel shading.
       */
      Fresnel = 0xa
   }

   /**
    * Defines some mixed flags for a particular texture.
    *
    * Usually you'll instruct your cg artists how textures have to look like
    * and how they will be processed in your application. However, if you use
    * Assimp for completely generic loading purposes you might also need to
    * process these flags in order to display as many 'unknown' 3D models as
    * possible correctly.
    *
    * This corresponds to the <code>AI_MATKEY_TEXFLAGS</code> property.
    */
   enum aiTextureFlags : uint {
      /**
       * The texture's color values have to be inverted (i.e. <code>1-n</code>
       * component-wise).
       */
      Invert = 0x1,

      /**
       * Explicit request to the application to process the alpha channel of the
       * texture.
       *
       * Mutually exclusive with <code>IgnoreAlpha</code>. These flags are
       * set if the library can say for sure that the alpha channel is used/is
       * not used. If the model format does not define this, it is left to the
       * application to decide whether the texture alpha channel – if any – is
       * evaluated or not.
       */
      UseAlpha = 0x2,

      /**
       * Explicit request to the application to ignore the alpha channel of the
       * texture.
       *
       * Mutually exclusive with <code>UseAlpha</code>.
       */
      IgnoreAlpha = 0x4
   }


   /**
    * Defines alpha-blend flags.
    *
    * If you're familiar with OpenGL or D3D, these flags aren't new to you.
    * They define how the final color value of a pixel is computed, based on
    * the previous color at that pixel and the new color value from the
    * material.
    *
    * The basic blending formula is
    * <code>SourceColor * SourceBlend + DestColor * DestBlend</code>,
    * where <code>DestColor</code> is the previous color in the framebuffer at
    * this position and <code>SourceColor</code> is the material color before
    * the transparency calculation.
    *
    * This corresponds to the <code>AI_MATKEY_BLEND_FUNC</code> property.
    */
   enum aiBlendMode :uint {
      /**
       * Formula:
       * <code>SourceColor * SourceAlpha + DestColor * (1 - SourceAlpha)</code>
       */
      Default = 0x0,

      /**
       * Additive blending.
       *
       * Formula: <code>SourceColor*1 + DestColor*1</code>
       */
      Additive = 0x1
   }

   /**
    * Defines how an UV channel is transformed.
    *
    * This is just a helper structure for the <code>AI_MATKEY_UVTRANSFORM</code>
    * key. See its documentation for more details.
    */
   struct aiUVTransform {
   align ( 1 ) :
      /**
       * Translation on the u and v axes.
       *
       * The default value is (0|0).
       */
      aiVector2D mTranslation;

      /**
       * Scaling on the u and v axes.
       *
       * The default value is (1|1).
       */
      aiVector2D mScaling;

      /**
       * Rotation - in counter-clockwise direction.
       *
       * The rotation angle is specified in radians. The rotation center is
       * 0.5|0.5. The default value is 0.
       */
      float mRotation;
   }

   /**
    * A very primitive RTTI system to store the data type of a material
    * property.
    */
   enum aiPropertyTypeInfo : uint {
      /**
       * Array of single-precision (32 bit) floats.
       *
       * It is possible to use <code>aiGetMaterialInteger[Array]()</code> to
       * query properties stored in floating-point format. The material system
       * performs the type conversion automatically.
       */
      Float = 0x1,

      /**
       * aiString property.
       *
       * Arrays of strings aren't possible, <code>aiGetMaterialString()</code>
       * must be used to query a string property.
       */
      String = 0x3,

      /**
       * Array of (32 bit) integers.
       *
       * It is possible to use <code>aiGetMaterialFloat[Array]()</code> to
       * query properties stored in integer format. The material system
       * performs the type conversion automatically.
       */
      Integer = 0x4,

      /**
       * Simple binary buffer, content undefined. Not convertible to anything.
       */
      Buffer = 0x5
   }

   /**
    * Data structure for a single material property.
    *
    * As an user, you'll probably never need to deal with this data structure.
    * Just use the provided <code>aiGetMaterialXXX()</code> functions to query
    * material properties easily. Processing them manually is faster, but it is
    * not the recommended way. It isn't worth the effort.
    *
    * Material property names follow a simple scheme:
    *
    * <code>$[name]</code>: A public property, there must be a corresponding
    * AI_MATKEY_XXX constant.
    *
    * <code>?[name]</code>: Also public, but ignored by the
    * <code>aiProcess.RemoveRedundantMaterials</code> post-processing step.
    *
    * <code>~[name]</code>: A temporary property for internal use.
    */
   struct aiMaterialProperty {
      /**
       * Specifies the name of the property (key).
       *
       * Keys are generally case insensitive.
       */
      aiString mKey;

      /**
       * For texture properties, this specifies the exact usage semantic.
       *
       * For non-texture properties, this member is always 0 (or rather
       * <code>aiTextureType.NONE</code>).
       */
      uint mSemantic;

      /**
       * For texture properties, this specifies the index of the texture.
       *
       * For non-texture properties, this member is always 0.
       */
      uint mIndex;

      /**
       * Size of the buffer <code>mData</code> is pointing to (in bytes).
       *
       * This value may not be 0.
       */
      uint mDataLength;

      /**
       * Type information for the property.
       *
       * Defines the data layout inside the data buffer. This is used by the
       * library internally to perform debug checks and to utilize proper type
       * conversions.
       */
      aiPropertyTypeInfo mType;

      /**
       * Binary buffer to hold the property's value.
       *
       * The size of the buffer is always <code>mDataLength</code>.
       */
      char* mData;
   }

   /**
    * Data structure for a material
    *
    * Material data is stored using a key-value structure. A single key-value
    * pair is called a <em>material property</em>. The properties can be
    * queried using the <code>aiMaterialGetXXX</code> family of functions. The
    * library defines a set of standard keys (AI_MATKEY_XXX).
    */
   struct aiMaterial {
      /**
       * List of all material properties loaded.
       */
      aiMaterialProperty** mProperties;

      /**
       * Number of properties loaded.
       */
      uint mNumProperties;
      uint mNumAllocated; /// ditto
   }

   /**
    * Standard material property keys. Always pass 0 for texture type and index
    * when querying these keys.
    */
   const char* AI_MATKEY_NAME = "?mat.name";
   const char* AI_MATKEY_TWOSIDED = "$mat.twosided"; /// ditto
   const char* AI_MATKEY_SHADING_MODEL = "$mat.shadingm"; /// ditto
   const char* AI_MATKEY_ENABLE_WIREFRAME = "$mat.wireframe"; /// ditto
   const char* AI_MATKEY_BLEND_FUNC = "$mat.blend"; /// ditto
   const char* AI_MATKEY_OPACITY = "$mat.opacity"; /// ditto
   const char* AI_MATKEY_BUMPSCALING = "$mat.bumpscaling"; /// ditto
   const char* AI_MATKEY_SHININESS = "$mat.shininess"; /// ditto
   const char* AI_MATKEY_REFLECTIVITY = "$mat.reflectivity"; /// ditto
   const char* AI_MATKEY_SHININESS_STRENGTH = "$mat.shinpercent"; /// ditto
   const char* AI_MATKEY_REFRACTI = "$mat.refracti"; /// ditto
   const char* AI_MATKEY_COLOR_DIFFUSE = "$clr.diffuse"; /// ditto
   const char* AI_MATKEY_COLOR_AMBIENT = "$clr.ambient"; /// ditto
   const char* AI_MATKEY_COLOR_SPECULAR = "$clr.specular"; /// ditto
   const char* AI_MATKEY_COLOR_EMISSIVE = "$clr.emissive"; /// ditto
   const char* AI_MATKEY_COLOR_TRANSPARENT = "$clr.transparent"; /// ditto
   const char* AI_MATKEY_COLOR_REFLECTIVE = "$clr.reflective"; /// ditto
   const char* AI_MATKEY_GLOBAL_BACKGROUND_IMAGE = "?bg.global"; /// ditto

   /**
    * Texture material property keys. Do not forget to specify texture type and
    * index for these keys.
    */
   const char* AI_MATKEY_TEXTURE = "$tex.file";
   const char* AI_MATKEY_UVWSRC = "$tex.uvwsrc"; /// ditto
   const char* AI_MATKEY_TEXOP = "$tex.op"; /// ditto
   const char* AI_MATKEY_MAPPING = "$tex.mapping"; /// ditto
   const char* AI_MATKEY_TEXBLEND = "$tex.blend"; /// ditto
   const char* AI_MATKEY_MAPPINGMODE_U = "$tex.mapmodeu"; /// ditto
   const char* AI_MATKEY_MAPPINGMODE_V = "$tex.mapmodev"; /// ditto
   const char* AI_MATKEY_TEXMAP_AXIS = "$tex.mapaxis"; /// ditto
   const char* AI_MATKEY_UVTRANSFORM = "$tex.uvtrafo"; /// ditto
   const char* AI_MATKEY_TEXFLAGS = "$tex.flags"; /// ditto
}