[英]OpenGL using VBO with index
因此,我正在构建一个用于渲染模型和转换的基本引擎,我使用常规VBO(无索引)完成了此工作,没有任何问题,但是我决定改为使用具有索引的VBO。 这是我代码的重要部分:
相关全局变量:
GLuint *modelBuffers;
GLuint *indexBuffers;
相关数据结构:
struct databaseStruct
{
int moveSize;
int modelSize;
int spinSize;
int tracerSize;
int currentMove;
int currentSpin;
int currentModel;
int currentTracer;
vector<moveNode> moveList;
vector<modelNode> modelList;
vector<spinNode> spinList;
vector<tracerNode> tracerList;
groupStruct scene;
} database;
struct modelNode
{
int id;
int numTri;
string modelName;
vector<GLfloat> model;
vector<GLfloat> normals;
vector<int> indices;
};
在程序开始时进行模型初始化:
void initModels(){
glEnableClientState(GL_VERTEX_ARRAY);
modelBuffers = new GLuint[database.modelSize];
indexBuffers = new GLuint[database.modelSize];
glGenBuffers(database.modelSize, modelBuffers);
glGenBuffers(database.modelSize, indexBuffers);
vector<modelNode> mList = database.modelList;
for (int i = 0; i < database.modelSize; i++){
glBindBuffer(GL_ARRAY_BUFFER, modelBuffers[mList[i].id]);
glBufferData(GL_ARRAY_BUFFER, mList[i].model.size()*sizeof(GLfloat), &(mList[i].model[0]), GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffers[mList[i].id]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, mList[i].indices.size() * sizeof(GLint), &(mList[i].indices[0]), GL_STATIC_DRAW);
}
}
在渲染场景上进行绘制调用:
void drawModel(element* elem){
if (elem != NULL){
modelNode *it = &database.modelList[elem->nodeRef];
glBindBuffer(GL_ARRAY_BUFFER, modelBuffers[it->id]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffers[it->id]);
glVertexPointer(3, GL_FLOAT, 0, 0);
glDrawElements(GL_TRIANGLES, it->numTri*3, GL_INT, 0);
}
}
程序的结构有效,因为自从使用简单的VBO以来,我所做的所有更改都是对结构的更改,以托管索引和用于处理索引的OpenGL调用。 如果需要,我可以提供以前的工作版本。
您要重叠缓冲区,为顶点信息和索引创建单独的缓冲区
void initModels(){
glEnableClientState(GL_VERTEX_ARRAY);
modelBuffers = new GLuint[database.modelSize*2];//twice as large
glGenBuffers(database.modelSize*2, modelBuffers);//creating twice as many
vector<modelNode> mList = database.modelList;
for (int i = 0; i < database.modelSize; i++){
glBindBuffer(GL_ARRAY_BUFFER, modelBuffers[mList[i].id*2]);
glBufferData(GL_ARRAY_BUFFER, mList[i].model.size()*sizeof(GLfloat), &(mList[i].model[0]), GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, modelBuffers[mList[i].id*2+1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, mList[i].indices.size() * sizeof(int), &(mList[i].indices[0]), GL_STATIC_DRAW);
}
}
void drawModel(element* elem){
if (elem != NULL){
modelNode *it = &database.modelList[elem->nodeRef];
glBindBuffer(GL_ARRAY_BUFFER, modelBuffers[it->id*2]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, modelBuffers[it->id*2+1]);
glVertexPointer(3, GL_FLOAT, 0, 0);
glDrawElements(GL_TRIANGLES, it->numTri*3, GL_INT, 0);
}
}
你会看到我创建的两倍尽可能多的缓冲区,并且每个数组缓冲区是id*2
在modelBuffers
和索引缓冲区是id*2 + 1
在modelBuffers
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