Question

我能够使用顶点数组绘制单个对象。但是，在绘制多个对象时，它给我带来了困难。

我有一个这样的数据数组，三个顶点渲染一个三角形：

-0.0570917f,0.490469f,-0.142433f
-0.0581126f,0.5f,-0.160615f
-0.0651903f,0.490827f,-0.147409f
-0.0501295f,0.499886f,-0.158146f
-0.0491703f,0.49039f,-0.140236f
-0.0422027f,0.499864f,-0.157942f
-0.041255f,0.49031f,-0.138206f
-0.0333885f,0.490314f,-0.137995f
-0.0967512f,0.48302f,-0.150394f
...

我正在尝试使用以下代码渲染多个三角形：

// this array contains arrays with one vertex (three elements)
vector<vector<GLfloat>> pointVertex;

// Render OpenGL here
for (int i = 0; i < pointVertex.size(); i++) {
    vector<GLfloat> temp = pointVertex[i];
    GLfloat *pointVertexArrayPoint = temp.data();
    glEnable(GL_POINT_SMOOTH);
    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3, GL_FLOAT, 0, pointVertexArrayPoint);
    glDrawArrays(GL_LINES, 0, temp.size());
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisable(GL_POINT_SMOOTH);
}

现在，我得到了一个结果，但一切都从同一点开始。我希望它呈现不同的多个独立三角形。我怎样才能改变它？

Answer 1

有几种方法可以做到这一点，而不会偏离你正在使用的技术（传统管道）..

下面的代码将绘制两个三角形..就像这样：

每个三角形呈现每个三角形1次绘制调用：

void onDisplayRefreshSO(void* ctx)
{
    //Setup OpenGL once..
    static std::once_flag flag;
    std::call_once(flag, []{
        GLfloat view_port[4] = {0};
        glGetFloatv(GL_VIEWPORT, &view_port[0]);
        GLfloat screen_width = view_port[2] - view_port[0];
        GLfloat screen_height = view_port[3] - view_port[1];

        glMatrixMode(GL_PROJECTION);
        gluPerspective(45.0, screen_width / screen_height, 0.1f, 1000.0f);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
        glClearDepth(1.0f);                                    // Depth Buffer Setup
        glEnable(GL_DEPTH_TEST);                            // Enables Depth Testing
        glDepthFunc(GL_LEQUAL);                                // The Type Of Depth Testing To Do
        glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);    // Really Nice Perspective Calculations
    });



    /** Setup Drawing Triangles **/
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);


    GLfloat normals[] = {
        0, 0, 1,   0, 0, 1,   0, 0, 1,
        0, 0, 1,   0, 0, 1,   0, 0, 1
    };

    GLfloat colors[] = {
        1, 1, 1,   1, 1, 0,   1, 0, 0,
        0, 1, 1,   0, 1, 0,   0, 0, 1
    };

    GLfloat vertices[] = {
        1, 1, 1,  -1, 1, 1,  -1,-1, 1,
        1, 1, 1,  1, -1, 1,  -1,-1, 1
    };



    //9 floats per triangle.. 3 * (X, Y, Z)..
    for (int i = 0; i < sizeof(vertices) / sizeof(vertices[0]) / 9; ++i)
    {
        glEnableClientState(GL_NORMAL_ARRAY);
        glEnableClientState(GL_COLOR_ARRAY);
        glEnableClientState(GL_VERTEX_ARRAY);
        glNormalPointer(GL_FLOAT, 0, normals + (i * 9));
        glColorPointer(3, GL_FLOAT, 0, colors + (i * 9));
        glVertexPointer(3, GL_FLOAT, 0, vertices + (i * 9));

        glPushMatrix();
        glTranslatef(-1.0f, 0.0f, -6.0f);
        glDrawArrays(GL_TRIANGLES, 0, 3); //3 vertices (X, Y, Z) per triangle..
        glPopMatrix();

        glDisableClientState(GL_VERTEX_ARRAY);
        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_NORMAL_ARRAY);
    }
}

在单个绘图调用中呈现的所有三角形：

void onDisplayRefreshSO2(void* ctx)
{
    //Setup OpenGL once..
    static std::once_flag flag;
    std::call_once(flag, []{
        GLfloat view_port[4] = {0};
        glGetFloatv(GL_VIEWPORT, &view_port[0]);
        GLfloat screen_width = view_port[2] - view_port[0];
        GLfloat screen_height = view_port[3] - view_port[1];

        glMatrixMode(GL_PROJECTION);
        gluPerspective(45.0, screen_width / screen_height, 0.1f, 1000.0f);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
        glClearDepth(1.0f);                                    // Depth Buffer Setup
        glEnable(GL_DEPTH_TEST);                            // Enables Depth Testing
        glDepthFunc(GL_LEQUAL);                                // The Type Of Depth Testing To Do
        glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);    // Really Nice Perspective Calculations
    });


    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);


    /** Setup Drawing Triangles **/
    GLfloat normals[] = {
        0, 0, 1,   0, 0, 1,   0, 0, 1,
        0, 0, 1,   0, 0, 1,   0, 0, 1
    };

    GLfloat colors[] = {
        1, 1, 1,   1, 1, 0,   1, 0, 0,
        0, 1, 1,   0, 1, 0,   0, 0, 1
    };

    GLfloat vertices[] = {
        1, 1, 1,  -1, 1, 1,  -1,-1, 1,
        1, 1, 1,  1, -1, 1,  -1,-1, 1
    };


    //Draw both triangles in a single call..
    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);
    glNormalPointer(GL_FLOAT, 0, normals);
    glColorPointer(3, GL_FLOAT, 0, colors);
    glVertexPointer(3, GL_FLOAT, 0, vertices);

    glPushMatrix();
    glTranslatef(-1.0f, 0.0f, -6.0f);
    glDrawArrays(GL_TRIANGLES, 0, (sizeof(vertices) / sizeof(vertices[0])) / 3); //6 vertices (X, Y, Z) for 2 triangles..
    glPopMatrix();

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);
}

Answer 2

好像你需要添加索引缓冲区。请参阅示例：http://www.opengl-tutorial.org/ru/intermediate-tutorials/tutorial-9-vbo-indexing/

管道：

填充顶点和索引缓冲区
绘制缓冲区

如何在OpenGL C ++中绘制多个三角形？

2 个答案: