我想使用Assimp将模型加载到D3D中。我想更多地了解Assimp如何处理索引，因为我无法以我理解的形式使用obj模型。例如，对于面为int / int / int的obj模型，当我遍历面数时：
for (unsigned int x = 0 ; x < paiMesh->mNumFaces ; ++x) {
const aiFace& Face = paiMesh->mFaces[x];
assert(Face.mNumIndices == 3);
for (unsigned int k = 0; k< nidx;k++)//triangle list
{
i1 = Face.mIndices[k];
Indices.push_back(i1);
}
}
我注意到我的指数向量似乎只包含递增顺序的数字，即指数= [0,1,2,3,4,5,6,7,8 ...]。这看起来与实际的obj文件完全不同。所以，谁能告诉我Assimp在这里做了什么。它可以帮助我理解我的加载代码出错的地方
答案 0 :(得分：2)
我明白了。虽然上面的代码是正确的，但我没有更正模型中的不同子集。这是我从Assimp加载顶点的代码。如果你想要我使用的全套课程，请留言。
/****************************************************
**********File name: MeshLoader03.cpp****************
******************************************************/
/*************Includes*****************************/
#include "stdafx.h"
#include "MeshLoader03.h"
/******************Class**************************/
bool MeshLoader03::LoadModel(const std::string& a_file, float a_scale,
std::vector<Vertex::Basic28>& vertices,
std::vector<USHORT>& indices,
std::vector<MeshGeometry::Subset>& subsets,
std::vector<ModelMaterial>& mats)
{
//check if file exists
std::ifstream fin(a_file.c_str());
if(!fin.fail())
{
fin.close();
}
else
{
MessageBox(NULL, TEXT("Couldn't open file: ") , TEXT("ERROR"), MB_OK | MB_ICONEXCLAMATION);
return false;
}
//Assign scale
m_scale = a_scale;
//Assign mesh properties
numVertices = 0;
numSubsets = 0;
numMaterials = 0;
numTriangles = 0;
//initialize success variable
bool Ret = false;
//Load mesh
Ret = loadMesh(a_file,a_scale, vertices,indices,subsets,mats);
//Return
return Ret;
}
//Load mesh with Assimp
bool MeshLoader03::loadMesh(const std::string& a_file, float a_scale,
std::vector<Vertex::Basic28>& vertices,
std::vector<USHORT>& indices,
std::vector<MeshGeometry::Subset>& subsets,
std::vector<ModelMaterial>& mats)
{
//Assimp importer we are using
Assimp::Importer importer;
const aiScene* loadedScene = importer.ReadFile( a_file,
aiProcessPreset_TargetRealtime_Quality |
aiProcess_ConvertToLeftHanded
);
//we have NO assimp object
if(!loadedScene)
{
OutputDebugString(L"Model failed to load \n");
//OutputDebugString( (importer.GetErrorString()).c_str() );
return false;
}
else
{ //we have an assimp object with meshes
if(loadedScene->HasMeshes())
{
//Get mesh properties
GetMeshProperties(loadedScene);
//Extract Faces,Vertices,Subsets,Materials
InitMaterials(a_file,loadedScene, numMaterials, mats);
InitSubsetTable(a_file,loadedScene,numSubsets,subsets);
InitVertices(a_file,loadedScene, numVertices, vertices);
InitTriangles(a_file,loadedScene, numTriangles, indices);
ScaleAsset(loadedScene);
return true;
}
else //an assimp object with NO meshes
return false;
}
}
//Get mesh properties
void MeshLoader03::GetMeshProperties(const aiScene* loadedScene)
{
//Get rootNode
aiNode* rootNode = loadedScene->mRootNode;
//Attributes
numSubsets = loadedScene->mNumMeshes;
numMaterials = loadedScene->mNumMaterials;
//If only one node
if(rootNode->mNumChildren == 0)
{
numVertices = loadedScene->mMeshes[0]->mNumVertices;
numTriangles = loadedScene->mMeshes[0]->mNumFaces;
}
else
{
//For all the children
for (size_t i =0 ;i<rootNode->mNumChildren; ++i)
{
//Get child node
aiNode* childNode = rootNode->mChildren[i];
// Initialize the meshes in the scene one by one
for (size_t n=0; n < childNode->mNumMeshes; ++n)
{
//get the mesh
const aiMesh* paiMesh = loadedScene->mMeshes[childNode->mMeshes[n]];
//Update total vertices and faces
numVertices+= paiMesh->mNumVertices;
numTriangles+= paiMesh->mNumFaces;
}
}
}
}
//Extract subsets
void MeshLoader03::InitSubsetTable(const std::string& a_file,const aiScene* pScene, UINT numSubsets, std::vector<MeshGeometry::Subset>& subsets)
{
subsets.resize(numSubsets);
//Get rootNode
aiNode* rootNode = pScene->mRootNode;
//Counter for vertices and indices
unsigned int vertexCounter, faceCounter;
//If only one node
if(rootNode->mNumChildren == 0)
{
subsets[0].Id = pScene->mMeshes[0]->mMaterialIndex;
subsets[0].VertexStart = 0;
subsets[0].VertexCount = pScene->mMeshes[0]->mNumVertices;
subsets[0].FaceStart = 0;
subsets[0].FaceCount = pScene->mMeshes[0]->mNumFaces;
}
else
{
//Counter
unsigned int subsetCounter = 0;
vertexCounter = 0; faceCounter = 0;
//For all the children
for (size_t i =0 ;i<rootNode->mNumChildren; ++i)
{
//Get child node
aiNode* childNode = rootNode->mChildren[i];
// Initialize the meshes in the scene one by one
for (size_t n=0; n < childNode->mNumMeshes; ++n)
{
//get the mesh
const aiMesh* paiMesh = pScene->mMeshes[childNode->mMeshes[n]];
subsets[subsetCounter].Id = pScene->mMeshes[childNode->mMeshes[n]]->mMaterialIndex;
subsets[subsetCounter].VertexStart = vertexCounter;
subsets[subsetCounter].VertexCount = paiMesh->mNumVertices;
subsets[subsetCounter].FaceStart = faceCounter;
subsets[subsetCounter].FaceCount = paiMesh->mNumFaces;
//Update total vertices and faces
vertexCounter+= paiMesh->mNumVertices;
faceCounter+= paiMesh->mNumFaces;
//Update counter
subsetCounter++;
}
}
}
}
//Extract Vertices
void MeshLoader03::InitVertices(const std::string& a_file,const aiScene* pScene, UINT numVertices, std::vector<Vertex::Basic28>& vertices)
{
vertices.resize(numVertices);
//Get rootNode
aiNode* rootNode = pScene->mRootNode;
//Counter for vertices and indices
unsigned int vertexCounter;
//If only one node
if(rootNode->mNumChildren == 0)
{
const aiMesh* mesh = pScene->mMeshes[0];
for(size_t b = 0;b<mesh->mNumVertices;b++)
{
vertices[b].Pos.x = mesh->mVertices[b].x;
vertices[b].Pos.y = mesh->mVertices[b].y;
vertices[b].Pos.z = mesh->mVertices[b].z;
if(mesh->HasVertexColors(0))
{
const aiColor4D pColr = mesh->mColors[0][b];
vertices[b].Color.x = pColr.r;
vertices[b].Color.y = pColr.g;
vertices[b].Color.z = pColr.b;
vertices[b].Color.w = pColr.a;
}
else
vertices[b].Color = XMFLOAT4(1.0f,1.0f,0.0f,0.0f);
}
}
else
{
//Counter
vertexCounter = 0;
//For all the children
for (size_t i =0 ;i<rootNode->mNumChildren; ++i)
{
//Get child node
aiNode* childNode = rootNode->mChildren[i];
// Initialize the meshes in the scene one by one
for (size_t n=0; n < childNode->mNumMeshes; ++n)
{
//get the mesh
const aiMesh* paiMesh = pScene->mMeshes[childNode->mMeshes[n]];
for(size_t b = 0;b<paiMesh->mNumVertices;b++)
{
vertices[vertexCounter].Pos.x = paiMesh->mVertices[b].x;
vertices[vertexCounter].Pos.y = paiMesh->mVertices[b].y;
vertices[vertexCounter].Pos.z = paiMesh->mVertices[b].z;
if(paiMesh->HasVertexColors(0))
{
const aiColor4D pColr = paiMesh->mColors[0][i];
vertices[vertexCounter].Color.x = pColr.r;
vertices[vertexCounter].Color.y = pColr.g;
vertices[vertexCounter].Color.z = pColr.b;
vertices[vertexCounter].Color.w = pColr.a;
}
else
vertices[vertexCounter].Color = XMFLOAT4(1.0f,1.0f,0.0f,0.0f);
vertexCounter++;
}
}
}
}
}
//Extract Triangles
void MeshLoader03::InitTriangles(const std::string& a_file,const aiScene* pScene, UINT numTriangles, std::vector<USHORT>& indices)
{
//indices.resize(numTriangles*3);
//Get rootNode
aiNode* rootNode = pScene->mRootNode;
//Counter for vertices and indices
unsigned int indexCounter, indexStart;
indexCounter = 0;
indexStart = indexCounter;
//If only one node
if(rootNode->mNumChildren == 0)
{
const aiMesh* mesh = pScene->mMeshes[0];
for(size_t b = 0;b<mesh->mNumFaces;b++)
{
indices[indexCounter++] = mesh->mFaces[b].mIndices[0] + indexStart;
indices[indexCounter++] = mesh->mFaces[b].mIndices[1] + indexStart;
indices[indexCounter++] = mesh->mFaces[b].mIndices[2] + indexStart;
}
}
else
{
//Counter
indexStart = 0;
indexCounter = 0;
//For all the children
for (size_t i =0 ;i<rootNode->mNumChildren; ++i)
{
//Get child node
aiNode* childNode = rootNode->mChildren[i];
// Initialize the meshes in the scene one by one
for (size_t n=0; n < childNode->mNumMeshes; ++n)
{
//get the mesh
const aiMesh* mesh = pScene->mMeshes[childNode->mMeshes[n]];
for(size_t b = 0;b<mesh->mNumFaces;b++)
{
//indices[indexCounter++] = mesh->mFaces[b].mIndices[0] + indexStart;
//indices[indexCounter++] = mesh->mFaces[b].mIndices[1] + indexStart;
//indices[indexCounter++] = mesh->mFaces[b].mIndices[2] + indexStart;
indices.push_back(mesh->mFaces[b].mIndices[0] + indexStart);
indices.push_back(mesh->mFaces[b].mIndices[1] + indexStart);
indices.push_back(mesh->mFaces[b].mIndices[2] + indexStart);
}
indexStart += mesh->mNumVertices;
}
}
}
}
/*********************Conversion functions**********************************/
//AiVector3 to XMFLOAT3
XMFLOAT3 MeshLoader03::aiVec3ToXMFloat3(const aiVector3D* vector)
{
//Ooutput
XMFLOAT3 output;
//Assignmetns
output.x = vector->x;
output.y = vector->y;
output.z = vector->z;
//Send back result
return output;
}
//AiColor to XMFLOAT4
XMFLOAT4 MeshLoader03::aiColorToXMFLOAT4(const aiColor4D* color)
{
//Ooutput
XMFLOAT4 output;
//Assignmetns
output.x = color->r;
output.y = color->g;
output.z = color->b;
output.w = color->a;
//Send back result
return output;
}
//AiMatrix to XMFLOAT4X4
XMFLOAT4X4 MeshLoader03::aiMatrixToXMFloat4x4(const aiMatrix4x4* aiMe)
{
XMFLOAT4X4 output;
output._11 = aiMe->a1;
output._12 = aiMe->a2;
output._13 = aiMe->a3;
output._14 = aiMe->a4;
output._21 = aiMe->b1;
output._22 = aiMe->b2;
output._23 = aiMe->b3;
output._24 = aiMe->b4;
output._31 = aiMe->c1;
output._32 = aiMe->c2;
output._33 = aiMe->c3;
output._34 = aiMe->c4;
output._41 = aiMe->d1;
output._42 = aiMe->d2;
output._43 = aiMe->d3;
output._44 = aiMe->d4;
return output;
}
/****************Scaling Functions: Taken from Assimp**********************/
//-------------------------------------------------------------------------------
// Calculate the boundaries of a given node and all of its children
// The boundaries are in Worldspace (AABB)
// piNode Input node
// p_avOut Receives the min/max boundaries. Must point to 2 vec3s
// piMatrix Transformation matrix of the graph at this position
//-------------------------------------------------------------------------------
int MeshLoader03::CalculateBounds(aiNode* piNode, aiVector3D* p_avOut,
const aiMatrix4x4& piMatrix, const aiScene* pcScene)
{
assert(NULL != piNode);
assert(NULL != p_avOut);
aiMatrix4x4 mTemp = piNode->mTransformation;
mTemp.Transpose();
const aiMatrix4x4 aiMe = mTemp * piMatrix;
for (unsigned int i = 0; i < piNode->mNumMeshes;++i)
{
for( unsigned int a = 0; a < pcScene->mMeshes[piNode->mMeshes[i]]->mNumVertices;++a)
{
const aiVector3D pc = pcScene->mMeshes[piNode->mMeshes[i]]->mVertices[a];
XMFLOAT3 pc11 = aiVec3ToXMFloat3(&pc);
XMFLOAT4X4 aiMe1 = aiMatrixToXMFloat4x4(&aiMe);
XMVECTOR pc1 = XMVector3TransformCoord(XMLoadFloat3(&pc11),XMLoadFloat4x4(&aiMe1));
p_avOut[0].x = min( p_avOut[0].x, pc1.m128_f32[0]);
p_avOut[0].y = min( p_avOut[0].y, pc1.m128_f32[1]);
p_avOut[0].z = min( p_avOut[0].z, pc1.m128_f32[2]);
p_avOut[1].x = max( p_avOut[1].x, pc1.m128_f32[0]);
p_avOut[1].y = max( p_avOut[1].y, pc1.m128_f32[1]);
p_avOut[1].z = max( p_avOut[1].z, pc1.m128_f32[2]);
}
}
for (unsigned int i = 0; i < piNode->mNumChildren;++i)
{
CalculateBounds( piNode->mChildren[i], p_avOut, aiMe, pcScene);
}
return 1;
}
//-------------------------------------------------------------------------------
// Scale the asset that it fits perfectly into the viewer window
// The function calculates the boundaries of the mesh and modifies the
// global world transformation matrix according to the aset AABB
//-------------------------------------------------------------------------------
int MeshLoader03::ScaleAsset(const aiScene* pcScene)
{
aiVector3D aiVecs[2] = {
aiVector3D( 1e10f, 1e10f, 1e10f),
aiVector3D( -1e10f, -1e10f, -1e10f) };
if (pcScene->mRootNode)
{
aiMatrix4x4 m;
CalculateBounds(pcScene->mRootNode,aiVecs,m, pcScene);
}
aiVector3D vDelta = aiVecs[1] - aiVecs[0];
aiVector3D vHalf = aiVecs[0] + (vDelta / 2.0f);
float fScale = 10.0f / vDelta.Length();
aiMatrix4x4 g_mWorld = aiMatrix4x4(
1.0f,0.0f,0.0f,0.0f,
0.0f,1.0f,0.0f,0.0f,
0.0f,0.0f,1.0f,0.0f,
-vHalf.x,-vHalf.y,-vHalf.z,1.0f) *
aiMatrix4x4(
fScale*m_scale,0.0f,0.0f,0.0f,
0.0f,fScale*m_scale,0.0f,0.0f,
0.0f,0.0f,fScale*m_scale,0.0f,
0.0f,0.0f,0.0f,1.0f);
m_World = aiMatrixToXMFloat4x4(&g_mWorld);
return 1;
}