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+Add vertex duplication during face normal generation (#5805)

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* +Add vertex duplication during face normal generation
`aiProcess_GenNormals` PostProcess now duplicates vertices if they are referenced by more than one polygon which results in the correct faceted appearance.

* Update GenFaceNormalsProcess.cpp

- Fix old spellings
- Use static_cast instead of c-style casts

---------

Co-authored-by: Kim Kulling <kimkulling@users.noreply.github.com>
This commit is contained in:
Tobias Rittig, Ph.D.
2024-11-02 09:03:59 +01:00
committed by GitHub
parent 401279e2f9
commit e06b80f6b0
1 changed files with 46 additions and 14 deletions
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60
code/PostProcessing/GenFaceNormalsProcess.cpp
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@@ -5,8 +5,6 @@ Open Asset Import Library (assimp)
Copyright (c) 2006-2024, assimp team
All rights reserved.
Redistribution and use of this software in source and binary forms,
@@ -41,9 +39,10 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
---------------------------------------------------------------------------
*/
/** @file Implementation of the post processing step to generate face
* normals for all imported faces.
*/
/**
* @file Implementation of the post-processing step to generate face
* normals for all imported faces.
*/
#include "GenFaceNormalsProcess.h"
#include <assimp/Exceptional.h>
@@ -55,7 +54,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
using namespace Assimp;
// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
// Returns whether the processing step is in the given flag field.
bool GenFaceNormalsProcess::IsActive(unsigned int pFlags) const {
force_ = (pFlags & aiProcess_ForceGenNormals) != 0;
flippedWindingOrder_ = (pFlags & aiProcess_FlipWindingOrder) != 0;
@@ -64,7 +63,7 @@ bool GenFaceNormalsProcess::IsActive(unsigned int pFlags) const {
}
// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
// Executes the post-processing step on the given imported data.
void GenFaceNormalsProcess::Execute(aiScene *pScene) {
ASSIMP_LOG_DEBUG("GenFaceNormalsProcess begin");
@@ -88,7 +87,7 @@ void GenFaceNormalsProcess::Execute(aiScene *pScene) {
}
// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
// Executes the post-processing step on the given imported data.
bool GenFaceNormalsProcess::GenMeshFaceNormals(aiMesh *pMesh) {
if (nullptr != pMesh->mNormals) {
if (force_) {
@@ -107,8 +106,27 @@ bool GenFaceNormalsProcess::GenMeshFaceNormals(aiMesh *pMesh) {
}
// allocate an array to hold the output normals
pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
const float qnan = get_qnan();
std::vector<aiVector3D> normals;
normals.resize(pMesh->mNumVertices);
// mask to indicate if a vertex was already referenced and needs to be duplicated
std::vector<bool> alreadyReferenced;
alreadyReferenced.resize(pMesh->mNumVertices, false);
std::vector<aiVector3D> duplicatedVertices;
auto storeNormalSplitVertex = [&](unsigned int index, const aiVector3D& normal) {
if (!alreadyReferenced[index]) {
normals[index] = normal;
alreadyReferenced[index] = true;
} else {
duplicatedVertices.push_back(pMesh->mVertices[index]);
normals.push_back(normal);
index = pMesh->mNumVertices + static_cast<unsigned int>(duplicatedVertices.size() - 1);
}
return index;
};
const aiVector3D undefinedNormal = aiVector3D(get_qnan());
// iterate through all faces and compute per-face normals but store them per-vertex.
for (unsigned int a = 0; a < pMesh->mNumFaces; a++) {
@@ -116,7 +134,7 @@ bool GenFaceNormalsProcess::GenMeshFaceNormals(aiMesh *pMesh) {
if (face.mNumIndices < 3) {
// either a point or a line -> no well-defined normal vector
for (unsigned int i = 0; i < face.mNumIndices; ++i) {
pMesh->mNormals[face.mIndices[i]] = aiVector3D(qnan);
face.mIndices[i] = storeNormalSplitVertex(face.mIndices[i], undefinedNormal);
}
continue;
}
@@ -124,15 +142,29 @@ bool GenFaceNormalsProcess::GenMeshFaceNormals(aiMesh *pMesh) {
const aiVector3D *pV1 = &pMesh->mVertices[face.mIndices[0]];
const aiVector3D *pV2 = &pMesh->mVertices[face.mIndices[1]];
const aiVector3D *pV3 = &pMesh->mVertices[face.mIndices[face.mNumIndices - 1]];
// Boolean XOR - if either but not both of these flags is set, then the winding order has
// changed and the cross product to calculate the normal needs to be reversed
// Boolean XOR - if either but not both of these flags are set, then the winding order has
// changed and the cross-product to calculate the normal needs to be reversed
if (flippedWindingOrder_ != leftHanded_)
std::swap(pV2, pV3);
const aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1)).NormalizeSafe();
for (unsigned int i = 0; i < face.mNumIndices; ++i) {
pMesh->mNormals[face.mIndices[i]] = vNor;
face.mIndices[i] = storeNormalSplitVertex(face.mIndices[i], vNor);
}
}
// store normals (and additional vertices) back into the mesh
if (!duplicatedVertices.empty()) {
const aiVector3D * oldVertices = pMesh->mVertices;
auto oldNumVertices = pMesh->mNumVertices;
pMesh->mNumVertices += static_cast<unsigned int>(duplicatedVertices.size());
pMesh->mVertices = new aiVector3D[pMesh->mNumVertices];
memcpy(pMesh->mVertices, oldVertices, oldNumVertices * sizeof(aiVector3D));
memcpy(pMesh->mVertices + oldNumVertices, duplicatedVertices.data(), duplicatedVertices.size() * sizeof(aiVector3D));
delete[] oldVertices;
}
pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
memcpy(pMesh->mNormals, normals.data(), normals.size() * sizeof(aiVector3D));
return true;
}