path: root/src/3rdparty/assimp/code/BlenderTessellator.cpp

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/** @file  BlenderTessellator.cpp
 *  @brief A simple tessellation wrapper
 */

#include "AssimpPCH.h"

#ifndef ASSIMP_BUILD_NO_BLEND_IMPORTER

#include "BlenderDNA.h"
#include "BlenderScene.h"
#include "BlenderBMesh.h"
#include "BlenderTessellator.h"

static const unsigned int BLEND_TESS_MAGIC = 0x83ed9ac3;

#if ASSIMP_BLEND_WITH_GLU_TESSELLATE

namspace Assimp
{
	template< > const std::string LogFunctions< BlenderTessellatorGL >::log_prefix = "BLEND_TESS_GL: ";
}

using namespace Assimp;
using namespace Assimp::Blender;

#ifndef CALLBACK
#define CALLBACK
#endif

// ------------------------------------------------------------------------------------------------
BlenderTessellatorGL::BlenderTessellatorGL( BlenderBMeshConverter& converter ):
	converter( &converter )
{
}

// ------------------------------------------------------------------------------------------------
BlenderTessellatorGL::~BlenderTessellatorGL( )
{
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::Tessellate( const MLoop* polyLoop, int vertexCount, const std::vector< MVert >& vertices )
{
	AssertVertexCount( vertexCount );

	std::vector< VertexGL > polyLoopGL;
	GenerateLoopVerts( polyLoopGL, polyLoop, vertexCount, vertices );

	TessDataGL tessData;
	Tesssellate( polyLoopGL, tessData );

	TriangulateDrawCalls( tessData );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::AssertVertexCount( int vertexCount )
{
	if ( vertexCount <= 4 )
	{
		ThrowException( "Expected more than 4 vertices for tessellation" );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::GenerateLoopVerts( std::vector< VertexGL >& polyLoopGL, const MLoop* polyLoop, int vertexCount, const std::vector< MVert >& vertices )
{
	for ( int i = 0; i < vertexCount; ++i )
	{
		const MLoop& loopItem = polyLoop[ i ];
		const MVert& vertex = vertices[ loopItem.v ];
		polyLoopGL.push_back( VertexGL( vertex.co[ 0 ], vertex.co[ 1 ], vertex.co[ 2 ], loopItem.v, BLEND_TESS_MAGIC ) );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::Tesssellate( std::vector< VertexGL >& polyLoopGL, TessDataGL& tessData )
{
	GLUtesselator* tessellator = gluNewTess( );
	gluTessCallback( tessellator, GLU_TESS_BEGIN_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateBegin ) );
	gluTessCallback( tessellator, GLU_TESS_END_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateEnd ) );
	gluTessCallback( tessellator, GLU_TESS_VERTEX_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateVertex ) );
	gluTessCallback( tessellator, GLU_TESS_COMBINE_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateCombine ) );
	gluTessCallback( tessellator, GLU_TESS_EDGE_FLAG_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateEdgeFlag ) );
	gluTessCallback( tessellator, GLU_TESS_ERROR_DATA, reinterpret_cast< void ( CALLBACK * )( ) >( TessellateError ) );
	gluTessProperty( tessellator, GLU_TESS_WINDING_RULE, GLU_TESS_WINDING_NONZERO );

	gluTessBeginPolygon( tessellator, &tessData );
	gluTessBeginContour( tessellator );

	for ( unsigned int i = 0; i < polyLoopGL.size( ); ++i )
	{
		gluTessVertex( tessellator, reinterpret_cast< GLdouble* >( &polyLoopGL[ i ] ), &polyLoopGL[ i ] );
	}

	gluTessEndContour( tessellator );
	gluTessEndPolygon( tessellator );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TriangulateDrawCalls( const TessDataGL& tessData )
{
	// NOTE - Because we are supplying a callback to GLU_TESS_EDGE_FLAG_DATA we don't technically
	//        need support for GL_TRIANGLE_STRIP and GL_TRIANGLE_FAN but we'll keep it here in case
	//        GLU tessellate changes or tristrips and fans are wanted.
	//        See: http://www.opengl.org/sdk/docs/man2/xhtml/gluTessCallback.xml
	for ( unsigned int i = 0; i < tessData.drawCalls.size( ); ++i )
	{
		const DrawCallGL& drawCallGL = tessData.drawCalls[ i ];
		const VertexGL* vertices = &tessData.vertices[ drawCallGL.baseVertex ];
		if ( drawCallGL.drawMode == GL_TRIANGLES )
		{
			MakeFacesFromTris( vertices, drawCallGL.vertexCount );
		}
		else if ( drawCallGL.drawMode == GL_TRIANGLE_STRIP )
		{
			MakeFacesFromTriStrip( vertices, drawCallGL.vertexCount );
		}
		else if ( drawCallGL.drawMode == GL_TRIANGLE_FAN )
		{
			MakeFacesFromTriFan( vertices, drawCallGL.vertexCount );
		}
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::MakeFacesFromTris( const VertexGL* vertices, int vertexCount )
{
	int triangleCount = vertexCount / 3;
	for ( int i = 0; i < triangleCount; ++i )
	{
		int vertexBase = i * 3;
		converter->AddFace( vertices[ vertexBase + 0 ].index, vertices[ vertexBase + 1 ].index, vertices[ vertexBase + 2 ].index );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::MakeFacesFromTriStrip( const VertexGL* vertices, int vertexCount )
{
	int triangleCount = vertexCount - 2;
	for ( int i = 0; i < triangleCount; ++i )
	{
		int vertexBase = i;
		converter->AddFace( vertices[ vertexBase + 0 ].index, vertices[ vertexBase + 1 ].index, vertices[ vertexBase + 2 ].index );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::MakeFacesFromTriFan( const VertexGL* vertices, int vertexCount )
{
	int triangleCount = vertexCount - 2;
	for ( int i = 0; i < triangleCount; ++i )
	{
		int vertexBase = i;
		converter->AddFace( vertices[ 0 ].index, vertices[ vertexBase + 1 ].index, vertices[ vertexBase + 2 ].index );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateBegin( GLenum drawModeGL, void* userData )
{
	TessDataGL& tessData = *reinterpret_cast< TessDataGL* >( userData );
	tessData.drawCalls.push_back( DrawCallGL( drawModeGL, tessData.vertices.size( ) ) );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateEnd( void* )
{
	// Do nothing
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateVertex( const void* vtxData, void* userData )
{
	TessDataGL& tessData = *reinterpret_cast< TessDataGL* >( userData );

	const VertexGL& vertex = *reinterpret_cast< const VertexGL* >( vtxData );
	if ( vertex.magic != BLEND_TESS_MAGIC )
	{
		ThrowException( "Point returned by GLU Tessellate was probably not one of ours. This indicates we need a new way to store vertex information" );
	}
	tessData.vertices.push_back( vertex );
	if ( tessData.drawCalls.size( ) == 0 )
	{
		ThrowException( "\"Vertex\" callback received before \"Begin\"" );
	}
	++( tessData.drawCalls.back( ).vertexCount );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateCombine( const GLdouble intersection[ 3 ], const GLdouble* [ 4 ], const GLfloat [ 4 ], GLdouble** out, void* userData )
{
	ThrowException( "Intersected polygon loops are not yet supported" );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateEdgeFlag( GLboolean, void* )
{
	// Do nothing
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorGL::TessellateError( GLenum errorCode, void* )
{
	ThrowException( reinterpret_cast< const char* >( gluErrorString( errorCode ) ) );
}

#endif // ASSIMP_BLEND_WITH_GLU_TESSELLATE

#if ASSIMP_BLEND_WITH_POLY_2_TRI

namespace Assimp
{
	template< > const std::string LogFunctions< BlenderTessellatorP2T >::log_prefix = "BLEND_TESS_P2T: ";
}

using namespace Assimp;
using namespace Assimp::Blender;

// ------------------------------------------------------------------------------------------------
BlenderTessellatorP2T::BlenderTessellatorP2T( BlenderBMeshConverter& converter ):
	converter( &converter )
{
}

// ------------------------------------------------------------------------------------------------
BlenderTessellatorP2T::~BlenderTessellatorP2T( )
{
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::Tessellate( const MLoop* polyLoop, int vertexCount, const std::vector< MVert >& vertices )
{
	AssertVertexCount( vertexCount );

	// NOTE - We have to hope that points in a Blender polygon are roughly on the same plane.
	//        There may be some triangulation artifacts if they are wildly different.

	std::vector< PointP2T > points;
	Copy3DVertices( polyLoop, vertexCount, vertices, points );

	PlaneP2T plane = FindLLSQPlane( points );

	aiMatrix4x4 transform = GeneratePointTransformMatrix( plane );

	TransformAndFlattenVectices( transform, points );

	std::vector< p2t::Point* > pointRefs;
	ReferencePoints( points, pointRefs );

	p2t::CDT cdt( pointRefs );

	cdt.Triangulate( );
	std::vector< p2t::Triangle* > triangles = cdt.GetTriangles( );

	MakeFacesFromTriangles( triangles );
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::AssertVertexCount( int vertexCount )
{
	if ( vertexCount <= 4 )
	{
		ThrowException( "Expected more than 4 vertices for tessellation" );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::Copy3DVertices( const MLoop* polyLoop, int vertexCount, const std::vector< MVert >& vertices, std::vector< PointP2T >& points ) const
{
	points.resize( vertexCount );
	for ( int i = 0; i < vertexCount; ++i )
	{
		const MLoop& loop = polyLoop[ i ];
		const MVert& vert = vertices[ loop.v ];

		PointP2T& point = points[ i ];
		point.point3D.Set( vert.co[ 0 ], vert.co[ 1 ], vert.co[ 2 ] );
		point.index = loop.v;
		point.magic = BLEND_TESS_MAGIC;
	}
}

// ------------------------------------------------------------------------------------------------
aiMatrix4x4 BlenderTessellatorP2T::GeneratePointTransformMatrix( const Blender::PlaneP2T& plane ) const
{
	aiVector3D sideA( 1.0f, 0.0f, 0.0f );
	if ( std::fabs( plane.normal * sideA ) > 0.999f )
	{
		sideA = aiVector3D( 0.0f, 1.0f, 0.0f );
	}

	aiVector3D sideB( plane.normal ^ sideA );
	sideB.Normalize( );
	sideA = sideB ^ plane.normal;

	aiMatrix4x4 result;
	result.a1 = sideA.x;
	result.a2 = sideA.y;
	result.a3 = sideA.z;
	result.b1 = sideB.x;
	result.b2 = sideB.y;
	result.b3 = sideB.z;
	result.c1 = plane.normal.x;
	result.c2 = plane.normal.y;
	result.c3 = plane.normal.z;
	result.a4 = plane.centre.x;
	result.b4 = plane.centre.y;
	result.c4 = plane.centre.z;
	result.Inverse( );

	return result;
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::TransformAndFlattenVectices( const aiMatrix4x4& transform, std::vector< Blender::PointP2T >& vertices ) const
{
	for ( unsigned int i = 0; i < vertices.size( ); ++i )
	{
		PointP2T& point = vertices[ i ];
		point.point3D = transform * point.point3D;
		point.point2D.set( point.point3D.y, point.point3D.z );
	}
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::ReferencePoints( std::vector< Blender::PointP2T >& points, std::vector< p2t::Point* >& pointRefs ) const
{
	pointRefs.resize( points.size( ) );
	for ( unsigned int i = 0; i < points.size( ); ++i )
	{
		pointRefs[ i ] = &points[ i ].point2D;
	}
}

// ------------------------------------------------------------------------------------------------
// Yes this is filthy... but we have no choice
#define OffsetOf( Class, Member ) ( static_cast< unsigned int >( \
	reinterpret_cast<uint8_t*>(&( reinterpret_cast< Class* >( NULL )->*( &Class::Member ) )) - \
	static_cast<uint8_t*>(NULL) ) )

inline PointP2T& BlenderTessellatorP2T::GetActualPointStructure( p2t::Point& point ) const
{
	unsigned int pointOffset = OffsetOf( PointP2T, point2D );
	PointP2T& pointStruct = *reinterpret_cast< PointP2T* >( reinterpret_cast< char* >( &point ) - pointOffset );
	if ( pointStruct.magic != static_cast<int>( BLEND_TESS_MAGIC ) )
	{
		ThrowException( "Point returned by poly2tri was probably not one of ours. This indicates we need a new way to store vertex information" );
	}
	return pointStruct;
}

// ------------------------------------------------------------------------------------------------
void BlenderTessellatorP2T::MakeFacesFromTriangles( std::vector< p2t::Triangle* >& triangles ) const
{
	for ( unsigned int i = 0; i < triangles.size( ); ++i )
	{
		p2t::Triangle& Triangle = *triangles[ i ];

		PointP2T& pointA = GetActualPointStructure( *Triangle.GetPoint( 0 ) );
		PointP2T& pointB = GetActualPointStructure( *Triangle.GetPoint( 1 ) );
		PointP2T& pointC = GetActualPointStructure( *Triangle.GetPoint( 2 ) );

		converter->AddFace( pointA.index, pointB.index, pointC.index );
	}
}

// ------------------------------------------------------------------------------------------------
inline float p2tMax( float a, float b )
{
	return a > b ? a : b;
}

// ------------------------------------------------------------------------------------------------
// Adapted from: http://missingbytes.blogspot.co.uk/2012/06/fitting-plane-to-point-cloud.html
float BlenderTessellatorP2T::FindLargestMatrixElem( const aiMatrix3x3& mtx ) const
{
	float result = 0.0f;

	for ( int x = 0; x < 3; ++x )
	{
		for ( int y = 0; y < 3; ++y )
		{
			result = p2tMax( std::fabs( mtx[ x ][ y ] ), result );
		}
	}

	return result;
}

// ------------------------------------------------------------------------------------------------
// Aparently Assimp doesn't have matrix scaling
aiMatrix3x3 BlenderTessellatorP2T::ScaleMatrix( const aiMatrix3x3& mtx, float scale ) const
{
	aiMatrix3x3 result;

	for ( int x = 0; x < 3; ++x )
	{
		for ( int y = 0; y < 3; ++y )
		{
			result[ x ][ y ] = mtx[ x ][ y ] * scale;
		}
	}

	return result;
}


// ------------------------------------------------------------------------------------------------
// Adapted from: http://missingbytes.blogspot.co.uk/2012/06/fitting-plane-to-point-cloud.html
aiVector3D BlenderTessellatorP2T::GetEigenVectorFromLargestEigenValue( const aiMatrix3x3& mtx ) const
{
	float scale = FindLargestMatrixElem( mtx );
	aiMatrix3x3 mc = ScaleMatrix( mtx, 1.0f / scale );
	mc = mc * mc * mc;

	aiVector3D v( 1.0f );
	aiVector3D lastV = v;
	for ( int i = 0; i < 100; ++i )
	{
		v = mc * v;
		v.Normalize( );
		if ( ( v - lastV ).SquareLength( ) < 1e-16f )
		{
			break;
		}
		lastV = v;
	}
	return v;
} 

// ------------------------------------------------------------------------------------------------
// Adapted from: http://missingbytes.blogspot.co.uk/2012/06/fitting-plane-to-point-cloud.html
PlaneP2T BlenderTessellatorP2T::FindLLSQPlane( const std::vector< PointP2T >& points ) const
{
	PlaneP2T result;

	aiVector3D sum( 0.0f );
	for ( unsigned int i = 0; i < points.size( ); ++i )
	{
		sum += points[ i ].point3D;
	}
	result.centre = sum * ( 1.0f / points.size( ) );

	float sumXX = 0.0f;
	float sumXY = 0.0f;
	float sumXZ = 0.0f;
	float sumYY = 0.0f;
	float sumYZ = 0.0f;
	float sumZZ = 0.0f;
	for ( unsigned int i = 0; i < points.size( ); ++i )
	{
		aiVector3D offset = points[ i ].point3D - result.centre;
		sumXX += offset.x * offset.x;
		sumXY += offset.x * offset.y;
		sumXZ += offset.x * offset.z;
		sumYY += offset.y * offset.y;
		sumYZ += offset.y * offset.z;
		sumZZ += offset.z * offset.z;
	}

	aiMatrix3x3 mtx( sumXX, sumXY, sumXZ, sumXY, sumYY, sumYZ, sumXZ, sumYZ, sumZZ );

	float det = mtx.Determinant( );
	if ( det == 0.0f )
	{
		result.normal = aiVector3D( 0.0f );
	}
	else
	{
		aiMatrix3x3 invMtx = mtx;
		invMtx.Inverse( );
		result.normal = GetEigenVectorFromLargestEigenValue( invMtx );
	}

	return result;
}

#endif // ASSIMP_BLEND_WITH_POLY_2_TRI

#endif // ASSIMP_BUILD_NO_BLEND_IMPORTER