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3Open Asset Import Library (assimp)
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41*/
42
43/** @file Implementation of the post processing step to invert
44 * all normals in meshes with infacing normals.
45 */
46
47// internal headers
48#include "FixNormalsStep.h"
49#include "StringUtils.h"
50#include <assimp/DefaultLogger.hpp>
51#include <assimp/postprocess.h>
52#include <assimp/scene.h>
53#include <stdio.h>
54
55
56using namespace Assimp;
57
58
59// ------------------------------------------------------------------------------------------------
60// Constructor to be privately used by Importer
61FixInfacingNormalsProcess::FixInfacingNormalsProcess()
62{
63 // nothing to do here
64}
65
66// ------------------------------------------------------------------------------------------------
67// Destructor, private as well
68FixInfacingNormalsProcess::~FixInfacingNormalsProcess()
69{
70 // nothing to do here
71}
72
73// ------------------------------------------------------------------------------------------------
74// Returns whether the processing step is present in the given flag field.
75bool FixInfacingNormalsProcess::IsActive( unsigned int pFlags) const
76{
77 return (pFlags & aiProcess_FixInfacingNormals) != 0;
78}
79
80// ------------------------------------------------------------------------------------------------
81// Executes the post processing step on the given imported data.
82void FixInfacingNormalsProcess::Execute( aiScene* pScene)
83{
84 DefaultLogger::get()->debug("FixInfacingNormalsProcess begin");
85
86 bool bHas = false;
87 for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
88 if(ProcessMesh( pScene->mMeshes[a],a))bHas = true;
89
90 if (bHas)
91 DefaultLogger::get()->debug("FixInfacingNormalsProcess finished. Found issues.");
92 else DefaultLogger::get()->debug("FixInfacingNormalsProcess finished. No changes to the scene.");
93}
94
95// ------------------------------------------------------------------------------------------------
96// Apply the step to the mesh
97bool FixInfacingNormalsProcess::ProcessMesh( aiMesh* pcMesh, unsigned int index)
98{
99 ai_assert(NULL != pcMesh);
100
101 // Nothing to do if there are no model normals
102 if (!pcMesh->HasNormals())return false;
103
104 // Compute the bounding box of both the model vertices + normals and
105 // the umodified model vertices. Then check whether the first BB
106 // is smaller than the second. In this case we can assume that the
107 // normals need to be flipped, although there are a few special cases ..
108 // convex, concave, planar models ...
109
110 aiVector3D vMin0 (1e10f,1e10f,1e10f);
111 aiVector3D vMin1 (1e10f,1e10f,1e10f);
112 aiVector3D vMax0 (-1e10f,-1e10f,-1e10f);
113 aiVector3D vMax1 (-1e10f,-1e10f,-1e10f);
114
115 for (unsigned int i = 0; i < pcMesh->mNumVertices;++i)
116 {
117 vMin1.x = std::min(vMin1.x,pcMesh->mVertices[i].x);
118 vMin1.y = std::min(vMin1.y,pcMesh->mVertices[i].y);
119 vMin1.z = std::min(vMin1.z,pcMesh->mVertices[i].z);
120
121 vMax1.x = std::max(vMax1.x,pcMesh->mVertices[i].x);
122 vMax1.y = std::max(vMax1.y,pcMesh->mVertices[i].y);
123 vMax1.z = std::max(vMax1.z,pcMesh->mVertices[i].z);
124
125 const aiVector3D vWithNormal = pcMesh->mVertices[i] + pcMesh->mNormals[i];
126
127 vMin0.x = std::min(vMin0.x,vWithNormal.x);
128 vMin0.y = std::min(vMin0.y,vWithNormal.y);
129 vMin0.z = std::min(vMin0.z,vWithNormal.z);
130
131 vMax0.x = std::max(vMax0.x,vWithNormal.x);
132 vMax0.y = std::max(vMax0.y,vWithNormal.y);
133 vMax0.z = std::max(vMax0.z,vWithNormal.z);
134 }
135
136 const float fDelta0_x = (vMax0.x - vMin0.x);
137 const float fDelta0_y = (vMax0.y - vMin0.y);
138 const float fDelta0_z = (vMax0.z - vMin0.z);
139
140 const float fDelta1_x = (vMax1.x - vMin1.x);
141 const float fDelta1_y = (vMax1.y - vMin1.y);
142 const float fDelta1_z = (vMax1.z - vMin1.z);
143
144 // Check whether the boxes are overlapping
145 if ((fDelta0_x > 0.0f) != (fDelta1_x > 0.0f))return false;
146 if ((fDelta0_y > 0.0f) != (fDelta1_y > 0.0f))return false;
147 if ((fDelta0_z > 0.0f) != (fDelta1_z > 0.0f))return false;
148
149 // Check whether this is a planar surface
150 const float fDelta1_yz = fDelta1_y * fDelta1_z;
151
152 if (fDelta1_x < 0.05f * std::sqrt( fDelta1_yz ))return false;
153 if (fDelta1_y < 0.05f * std::sqrt( fDelta1_z * fDelta1_x ))return false;
154 if (fDelta1_z < 0.05f * std::sqrt( fDelta1_y * fDelta1_x ))return false;
155
156 // now compare the volumes of the bounding boxes
157 if (std::fabs(fDelta0_x * fDelta0_y * fDelta0_z) <
158 std::fabs(fDelta1_x * fDelta1_yz))
159 {
160 if (!DefaultLogger::isNullLogger())
161 {
162 char buffer[128]; // should be sufficiently large
163 ai_snprintf(buffer,128,"Mesh %u: Normals are facing inwards (or the mesh is planar)",index);
164 DefaultLogger::get()->info(buffer);
165 }
166
167 // Invert normals
168 for (unsigned int i = 0; i < pcMesh->mNumVertices;++i)
169 pcMesh->mNormals[i] *= -1.0f;
170
171 // ... and flip faces
172 for (unsigned int i = 0; i < pcMesh->mNumFaces;++i)
173 {
174 aiFace& face = pcMesh->mFaces[i];
175 for( unsigned int b = 0; b < face.mNumIndices / 2; b++)
176 std::swap( face.mIndices[b], face.mIndices[ face.mNumIndices - 1 - b]);
177 }
178 return true;
179 }
180 return false;
181}
182