Fastest way to load arrays of vertices and face indices into OpenGL-ES?

问题

I'm trying to load .obj files that I've formatted into:

vertexX vertexY vertexZ normalX normalY normalZ

and:

index1 index2 index3

format into vector and vector arrays, which I then directly render in Opengl-ES. My problem is, when I try to load the model into the arrays, it takes about 40 seconds to load them in. I'm not sure why it's going so slow, I've seen others code load the same model in just a few seconds. Any suggestions? My code for loading the file is below:

-(void)loadModel:(NSString*)filePath
{
    try {

    ifstream objFile([filePath UTF8String]);
    objFile >> numVertices;
    objFile.ignore(128, '\n');
    vertices.resize(numVertices*6);
    VertexNormal* vertex = (VertexNormal*) &vertices[0];
    svec3* faceDef;

    while (objFile) {
        char c = objFile.get();

        switch (c) {
            case 'v':
            {
                objFile >> vertex->vertices.x >> vertex->vertices.y >> vertex->vertices.z
                >> vertex->normals.x >> vertex->normals.y >> vertex->normals.z;
                vertex++;
                break;
            }
            case 'f':
            {
                objFile >> faceDef->x >> faceDef->y >> faceDef->z;
                faceDef++;
                break;
            }
            case '#':
            {
                part newPart;
                partList.push_back(newPart);
                numObjects++;
                objFile.ignore(128, '\n');
                int numFaces;
                objFile >> numFaces;
                partList[partList.size()-1].faces.resize(numFaces*3);
                partList[partList.size()-1].numFaces = numFaces;
                faceDef = (svec3*) &partList[partList.size()-1].faces[0];
                break;
            }
            default:
                break;
        }
        objFile.ignore(128, '\n');
    }
    objFile.close();
    free(objFile);
    } catch (NSException *ex) {
        NSLog(@"%@", [ex reason]);
    }
}

One line of thought I had was to serialize the arrays into a binary file, then just deserialize them straight into my program. Haven't figured out how to do that yet though, but maybe something along those lines might be a solution.

回答1:

The best practice in game industry is to keep all models data in binary format, so you can very fast load whole non-interleaved blocks of memory that can be represented as vertices, normals or anything else. All you need for this - make small command line tool for converting text .obj files into your own binary file.

Also:

• Did you try to do text loading with stdio library, not stl ifstream?
• Maybe try to read all the text data once and fill arrays from memory, not from filesystem?
• how much parts in file do you have? Each resize of std::vector leads to new allocation and copying. Try to reserve space in std::vector, if you know desired volume before.

回答2:

I don't know if you've considered this, but if your .obj files won't change in your application, you can format them as objective-C arrays and compile them directly with your code.

来源：https://stackoverflow.com/questions/4328412/fastest-way-to-load-arrays-of-vertices-and-face-indices-into-opengl-es