OpenGL：设置索引/顶点 [英] OpenGL: setting up indices/vertices
本文介绍了OpenGL：设置索引/顶点的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我一直在尝试在c ++中编写一个非常简单的.obj模型加载器，但在我的两个方法中，模型不能正确显示，我也想知道这两个方法中哪一个更快/更好，为什么。这是我的第一个方法：
//顶点和索引是类Model的私有成员
//与size和indexCount相同
void Model :: loadModel（std :: string source）
{
using namespace std;
string name = source.substr（0，source.find（'。'））;
cout<<=== LOADING：<<< name<<===<
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跳过空格
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<<顶点数量：<<<<<< endl;
cout<<Index of indexes：<<< indexCountForFilling<< endl;
cout<<=== ENDED LOADING：<<< name<<===<
file.close（）;
}
这是使用stringstreams的第二种方法：
void Model :: loadModel2（std :: string source）
{
using namespace std;
string name = source.substr（0，source.find（。））;
cout<<+++ LOADING ::<<< name<<+++<
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（line）;
string type;
在>>类型中;
if（type ==v）
{
float x，y，z;
在>> x>> y>> z;
vertices [count ++] = x;
vertices [count ++] = y;
vertices [count ++] = z;
}
else if（type ==f）
{
float x，y，z;
在>> x>> y>> z;
indices [index ++] = x;
indices [index ++] = y;
indices [index ++] = z;
}
}
file.close（）;
cout<<+++ ENDED LOADING：<<< name<<+++<
}
这两个都是初始化的代码：
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）;
最后这是正在渲染的代码：
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）;
这是我应该得到的结果：
这是我得到的结果：
正如你可以看到，它几乎完美加载，直到最后几个三角形
所以总而言之，我的两个问题是：
- 这两种方法中的哪一种是从txt文件加载的最好的方法？
- 我做渲染的错误吗？
编辑：我的猜测是，我使用错误的索引，简单文件与较少的顶点/索引，并比较每个数字的输出，似乎我已经正确地复制数据到我的应用程序。所以我的猜测是，我在我的初始化代码为openGL的错误，任何人都可以找到错误？一切都编译好...
解决方案
不要这样做
while（file.good（））{...}
<
while（std :: getline（...））{...}
这是因为之后的标志（ eof / 坏 / etc。 / em>输入操作失败。这意味着你会循环，因为一切都会好起来，但是 std :: getline 失败，因为它在文件的结尾，但你仍然试图解析wasn' t阅读。
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:
This is the result i get:
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...
解决方案
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.
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