在OpenGL中的3D模型上创建AABB

Question

我正在尝试在OpenGL中的3D模型上创建AABB。当我使用顶点均为 1.0 的 3D box.obj 时，我在检测模型之间的碰撞时没有问题。但是，当我使用具有不同顶点值的更复杂的 3D 模型时，就会出现问题。复杂模型比 box.obj 小，顶点值为 .18 和 .06，因此它们上的边界框非常大，我的引擎会在对象不接触时检测到对象之间的碰撞。此问题的解决方案是在将模型读取到我的游戏中时跟踪每个 x、y 和 z 轴的最大值/最小值，但我在这样做时遇到了麻烦。

以下是我在模型中读取的代码：

bool Model::buffer(string objFile)
{
vector<vec3> locs;
vector<vec2> uvs;
vector<vec3> norms;
vector<VertInd> vertInds;
// Open file for reading
ifstream inFile;
inFile.open(objFile);
string line;
if (inFile.is_open())
{
    // Enter a loop that reads every line iteration from file until file is empty
    while (getline(inFile, line))
    {
        istringstream ss(line);
        string lineLabel;
        // Read a string (the line label) from the line
        ss >> lineLabel;
        if (lineLabel == "v") // Vertices
        {
            float a, b, c;
            ss >> a >> b >> c;
            locs.push_back(vec3(a, b, c));
        }
        else if (lineLabel == "vt") // Texture Coordinates
        {
            float a, b;
            ss >> a >> b;
            uvs.push_back(vec2(a, b));
        }
        else if (lineLabel == "vn") // Vertex Normals
        {
            float a, b, c;
            ss >> a >> b >> c;
            norms.push_back(vec3(a, b, c));
        }
        // Get indices
        else if (lineLabel == "f")
        {
            // do three times
            for (int i = 0; i < 3; i++)
            {
                unsigned int a, b, c;
                char s1, s2;
                // Read int, then char slash
                ss >> a >> s1 >> b >> s2 >> c;
                // Decrement each of the ints by 1
                vertInds.push_back(VertInd{ a - 1, b - 1, c - 1 });
            }
        }
        /* GLfloat min_x, max_x, min_y, max_y, min_z, max_z;
        min_x = max_x = locs[0].x;
        min_y = max_y = locs[0].y;
        min_z = max_z = locs[0].z;
        for (int i = 0; i < locs.size(); i++)
        {
            if (locs[i].x < min_x) min_x = locs[i].x;
            if (locs[i].x > max_x) max_x = locs[i].x;
            if (locs[i].y < min_y) min_y = locs[i].y;
            if (locs[i].y > max_y) max_y = locs[i].y;
            if (locs[i].z < min_z) min_z = locs[i].z;
            if (locs[i].z > max_z) max_z = locs[i].z;
        }
        vec3 size = vec3(max_x - min_x, max_y - min_y, max_z - min_z);
        vec3 center = vec3((min_x + max_x) / 2, (min_y + max_y) / 2, (min_z + max_z) / 2);
        mat4 transform = translate(mat4(1), center) * scale(mat4(1), size);
        mat4 m = camera.camMat * transform;
        glUniformMatrix4fv(2, 1, GL_FALSE, &m[0][0]); */
    }
    // Close the file
    inFile.close();
}
vertCount = vertInds.size();
GLuint vertBuf;
vector<Vertex> vertBufData(vertCount);
for (unsigned int i = 0; i < vertCount; i++)
    vertBufData[i] = { locs[vertInds[i].locInd], uvs[vertInds[i].uvInd], norms[vertInds[i].normInd] };
// Vertex array
glGenVertexArrays(1, &vertArr);
glGenBuffers(1, &vertBuf);
// Buffer data
glBindVertexArray(vertArr);
glBindBuffer(GL_ARRAY_BUFFER, vertBuf);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) *vertCount, &vertBufData[0], GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)sizeof(vec3)); // (void*)sizeof(VertInd));
glEnableVertexAttribArray(4);
glVertexAttribPointer(4, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)(sizeof(vec3) + sizeof(vec2)));
glBindVertexArray(0);
//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
return true;

}

注释掉的部分/**/是我最近添加的部分，试图获取最小/最大顶点值并使我的模型居中，但现在场景甚至无法加载。

Answer 1

请参阅此处的使用示例：

// return the min/max points of pts
template< typename Vec >
pair< Vec, Vec > GetExtents( const Vec* pts, size_t stride, size_t count )
{
    unsigned char* base = (unsigned char*)pts;
    Vec pmin( *(Vec*)base );
    Vec pmax( *(Vec*)base );
    for( size_t i = 0; i < count; ++i, base += stride )
    {
        const Vec& pt = *(Vec*)base;
        pmin = glm::min( pmin, pt );
        pmax = glm::max( pmax, pt );
    }
    return make_pair( pmin, pmax );
}
// centers geometry around the origin
// and scales it to fit in a size^3 box
template< typename Vec > 
void CenterAndScale( Vec* pts, size_t stride, size_t count, const typename Vec::value_type& size )
{
    typedef typename Vec::value_type Scalar;
    // get min/max extents
    pair< Vec, Vec > exts = GetExtents( pts, stride, count );
    // center and scale 
    const Vec center = ( exts.first * Scalar( 0.5 ) ) + ( exts.second * Scalar( 0.5f ) );
    const Scalar factor = size / glm::compMax( exts.second - exts.first );
    unsigned char* base = (unsigned char*)pts;
    for( size_t i = 0; i < count; ++i, base += stride )
    {
        Vec& pt = *(Vec*)base;
        pt = ( ( pt - center ) * factor );
    }    
}