问题
I have been trying to write a very simple .obj model loader in c++ but in both of my methods the model doesn't get displayed correctly and I would also like to know which of the 2 methods is faster/better and why. this is my first method:
//vertices&indices are private members of the class "Model"
//same with size and indexCount
void Model::loadModel(std::string source)
{
using namespace std;
string name = source.substr(0,source.find('.'));
cout<<"===LOADING: "<<name<<"==="<<endl;
ifstream file;
file.open(source);
string line,v0="",v1="",v2="";
string v3="",v4="",v5="";
int indexCount = 0;
while(file.good())
{
getline(file,line);
if(line[0] =='v') size++;
if(line[0] =='f') indexCount++;
}
file.close();
size *= 3;
vertices = new float[size];
indexSize = indexCount*3;
indices = new short[indexSize];
int count = 0;
int indexCountForFilling =0;
file.open(source);
while(file.good())
{
getline(file,line);
if(line[0] == 'v')
{
line = line.substr(2,line.length());
int oldindex =0;
v0 = line.substr(0,line.find(" "));
v1 = line.substr(line.find(" "),line.rfind(" ",line.find(" ")));
v2 = line.substr(line.rfind(" ",line.find(" ")),line.length());
v2 = v2.substr(line.find(" ")+2,v2.length());
//1
float temp = atof(v0.c_str());
vertices[count] = temp;
count++;
//2
temp = atof(v1.c_str());
vertices[count] = temp;
count++;
//3
temp = atof(v2.c_str());
vertices[count] = temp;
count++;
}
else if(line[0] == 'f')
{
line = line.substr(2,line.length());
int firstIndex = line.find(" ");
v3 = line.substr(0,firstIndex);
line = line.substr(firstIndex+1,line.length()); //+1 to skip space
int secondIndex = line.find(" ");
v4 = line.substr(0,secondIndex);
line = line.substr(secondIndex,line.length());
if(secondIndex+1>=line.length())
v5 = line.substr(0,line.length());
else
v5 = line.substr(1,line.length()); //zelfde
//1
short temp = atof(v3.c_str());
indices[indexCountForFilling] = temp;
indexCountForFilling++;
//2
temp = atof(v4.c_str());
indices[indexCountForFilling] = temp;
indexCountForFilling++;
//3
temp = atof(v5.c_str());
indices[indexCountForFilling] = temp;
indexCountForFilling++;
}
}
cout<<"Amount of vertices: "<<size<<endl;
cout<<"Amount of indexes: "<<indexCountForFilling<<endl;
cout<<"===ENDED LOADING: "<<name<<"==="<<endl;
file.close();
}
This is the second method using stringstreams:
void Model::loadModel2(std::string source)
{
using namespace std;
string name = source.substr(0,source.find("."));
cout<<"+++LOADING::"<<name<<"+++"<<endl;
ifstream file;
file.open(source);
string line;
while(file.good())
{
getline(file,line);
if(line[0]=='v') size++;
if(line[0]=='f') indexSize++;
}
size *= 3;
vertices = new GLfloat[size];
indexSize *= 3;
indices = new GLshort[indexSize];
cout<<"\tSize: "<<size<<endl;
cout<<"\tIndexSize:"<<indexSize<<endl;
file.close();
file.open(source);
int count = 0;
int index = 0;
while(file.good())
{
getline(file,line);
istringstream in(line);
string type;
in>>type;
if(type=="v")
{
float x,y,z;
in >> x >> y >> z;
vertices[count++] = x;
vertices[count++] = y;
vertices[count++] = z;
}
else if(type == "f")
{
float x,y,z;
in >> x >> y >> z;
indices[index++] = x;
indices[index++] = y;
indices[index++] = z;
}
}
file.close();
cout<<"+++ENDED LOADING:"<<name<<"+++"<<endl;
}
This is the code where both are initialized:
glGenBuffers(1,&vbo);
glBindBuffer(GL_ARRAY_BUFFER,vbo);
GLfloat model_test[834]; //834
memset(model_test,0.0f,sizeof(model_test));
for(unsigned int i=0;i<834;i++) model_test[i] = model.getIndex(i);
glBufferData(GL_ARRAY_BUFFER,sizeof(model_test),&model_test,GL_STATIC_DRAW);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,BUFFER_OFFSET(0));
glEnableVertexAttribArray(0);
GLuint ibo;
glGenBuffers(1,&ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,ibo);
GLshort indices[1656];//1656
memset(indices,0,sizeof(indices));
for(int i=0;i<1656;i++) indices[i] = model.getVertexIndex(i);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices),&indices,GL_STATIC_DRAW);
And finally this is the code where it is being rendered:
glBindVertexArray(vao);
if(rasterize)glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
else glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
glDrawElements(GL_TRIANGLES,model.getIndexSize(),GL_UNSIGNED_SHORT,0);
This is the result i should get:
http://imgur.com/OGGDLFq
This is the result i get:
http://imgur.com/U9ZTGsG
As you can see it loads almost perfectly until the last few triangles
So in conclusion my 2 questions are:
- Which of the 2 methods is the best way to load from a txt file?
- Am I doing something wrong with the rendering?
EDIT: My guess is that i'm use the wrong indices, however i've loaded a more simple file with fewer vertices/indices and compared the output of each number and it seems i've correctly copied the data into my application. So my guess is that i did something wrong in my initialization code for openGL, could anyone find the error? Everything compiles fine...
回答1:
Don't do e.g.
while (file.good()) { ... }
or similar, it will not do what you think it does.
Instead do
while (std::getline(...)) { ... }
It's because the flags (eof/bad/etc.) will not be set until after the input operation fails. This means that you will loop because everything will look good, but then std::getline fails because it's at the end of the file but you still try to parse data that wasn't read.
来源：https://stackoverflow.com/questions/18130006/opengl-setting-up-indices-vertices