Question

我正在使用SFML，OpenGL和VC ++编译器。当我渲染某些东西时，它只会在第二次运行时正确弹出（？）。这是我的代码：

void Renderer::initializeOpenGL() {
    glEnable(GL_DEPTH_TEST);
    glEnableClientState(GL_VERTEX_ARRAY);
    glOrtho(0, 1024, 0, 576, 0, 1024);
}

void Renderer::drawWorld(World* world) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glColor3f(1.F, 1.F, 1.F);
    std::vector<int> vertices;
    for(unsigned int x = 0; x < world->width; x++) {
        bool left = false, right = false;
        if(x == 0)
            left = true;
        else if(x == world->width -1)
            right = true;
        for(unsigned int z = 0; z < world->depth; z++) {
            bool front = false, back = false;
            if(z == 0)
                front = true;
            else if(z == world->depth -1)
                back = true;
            for(unsigned int y = 0; y < world->height; y++) {
                if(!world->blocks[x][z][y])
                    continue;
                if(left == true || !world->blocks[x-1][z][y]) {
                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z+1);

                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);

                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z);
                }
                if(right == true || !world->blocks[x+1][z][y]) {
                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z+1);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z);
                }

                if(front == true || !world->blocks[x][z-1][y]) {
                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z+1);

                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z+1);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);

                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);
                }
                if(back == true || !world->blocks[x][z+1][y]) {
                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z);

                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z);
                }

                if(y == 0 || !world->blocks[x][z][y-1]) {
                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y);
                    vertices.push_back(z+1);

                    vertices.push_back(x);
                    vertices.push_back(y);
                    vertices.push_back(z+1);
                }
                if(y == world->height -1 || !world->blocks[x][z][y+1]) {
                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z);

                    vertices.push_back(x+1);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);

                    vertices.push_back(x);
                    vertices.push_back(y+1);
                    vertices.push_back(z+1);
                }
            }
        }
    }

    glVertexPointer(3, GL_INT, 0, &vertices[0]);
    glDrawArrays(GL_QUADS, 0, vertices.size() /3);
    std::cout << "Vertices: " << vertices.size() << std::endl;
}

以下是我的结果：
第一次使用drawWorld：http://i.imgur.com/yMchEG9.png
drawWorld的第二次召唤：http://i.imgur.com/d9swgao.png

显然，在第一次调用之前，initializeOpenGL只被调用一次。提供的代码之外没有OpenGL语句。

Answer 1

<强>更新

显然，正如通过我的回答评论所讨论的，我的做法是错误的。用户derhass在评论中指出了什么是正确的。引自derhass：

没有。 GL是状态机。无论国家如何设定都无关紧要当他们不使用。对于顶点数组状态，重要的是画电话。您必须确保启用所需的所有阵列并且在绘制调用时禁用所有不需要的东西。实际上，最好避免不必要的状态变化。

导致此次更新的错误假设：

void Renderer::initializeOpenGL() {
    glEnable(GL_DEPTH_TEST);
    glEnableClientState(GL_VERTEX_ARRAY);
    glOrtho(0, 1024, 0, 576, 0, 1024);
}

glEnableClientState实际上不是这样的。您需要在绘制调用之前启用客户端状态，并在之后禁用它。

所以我看到你在抽签结束后错过了glDisableClientState(GL_VERTEX_ARRAY);。同样从initializeOpenGL（）函数中删除glEnableClientState(GL_VERTEX_ARRAY);并将其放在drawWorld函数中（编辑：在你的vertexpointer调用之前）。

这可能会导致您的问题。

OpenGL仅适用于第二帧

1 个答案: