c++ - OpenGL 按面着色

Question

我是 OpenGL 的新手，我正在处理一个小项目。该项目的一部分是创建一个网格，允许网格的某些部分具有不同的颜色。

例如整个网格是绿色的，但网格上的一个 block 亮红色，也许另一个 block 亮黄色。

我在使用索引时使用 GL_TRIANGLE_STRIP 绘制此网格。在那个阶段之后，我还在同一个顶点数据数组中包含了颜色。但输出不是我想要的样子。

首先有一个插值，我试图通过为颜色添加“平坦”标志来删除它。但似乎有一个重叠的问题。这导致了这个 picture .

有没有办法创建一个网格。网格 block 的颜色可以与网格不同。

更新这是我的 GL_TRIANGLES 代码

short* Grid::Indicies()
{
    const int X_GRID_SIZE = X_GRID_SIZE_;
    const int Y_GRID_SIZE = Y_GRID_SIZE_;
    const int INDICIES_SIZE = (((X_GRID_SIZE * 4) + ((X_GRID_SIZE_ - 3) * 2)) * Y_GRID_SIZE);

    short* indicies = new short[INDICIES_SIZE];
    int index = 0;

    for (size_t y = 0; y < Y_GRID_SIZE_; y++)
    {
        // Current, Down, Right, Down
        indicies[index++] = (short)(y * X_GRID_SIZE_);
        indicies[index++] = (short)((y + 1) * X_GRID_SIZE_);
        indicies[index++] = (short)((y * X_GRID_SIZE_) + 1);
        indicies[index++] = (short)((y + 1) * X_GRID_SIZE_);

        for (size_t x = 1; x < X_GRID_SIZE_ - 1; x++)
        {
            // Current, Down, Current, Down, Right, Down
            for (size_t i = 0; i < 2; i++)
            {
                indicies[index++] = (short)((y * X_GRID_SIZE_) + x);
                indicies[index++] = (short)(((y + 1) * X_GRID_SIZE_) + x);
            }
            indicies[index++] = (short)((y * X_GRID_SIZE_) + x + 1);
            indicies[index++] = (short)(((y + 1) * X_GRID_SIZE_) + x);
        }
        // Current, Down
        indicies[index++] = (short)(((y + 1) * X_GRID_SIZE_) - 1);
        indicies[index++] = (short)(((y + 2) * X_GRID_SIZE_) - 1);
    }
    indicies_size_ = index;
    return (indicies);
}

GLfloat vertices[] = {
    // Position                 // Color
    -1.0f,  1.0f,  0.0f,       1.0f,  0.0f,  0.0f, 
    -0.5f,  1.0f,  0.0f,       1.0f,  0.0f,  0.0f, 
     0.0f,  1.0f,  0.0f,       1.0f,  0.0f,  0.0f, 
     0.5f,  1.0f,  0.0f,       1.0f,  0.0f,  0.0f, 
     1.0f,  1.0f,  0.0f,       1.0f,  0.0f,  0.0f, 

    -1.0f,  0.5f,  0.0f,       1.0f,  0.0f,  0.0f, 
    -0.5f,  0.5f,  0.0f,       1.0f,  0.0f,  0.0f, 
     0.0f,  0.5f,  0.0f,       1.0f,  0.0f,  0.0f, 
     0.5f,  0.5f,  0.0f,       1.0f,  0.0f,  0.0f, 
     1.0f,  0.5f,  0.0f,       1.0f,  0.0f,  0.0f, 

    -1.0f,  0.0f,  0.0f,       1.0f,  0.0f,  0.0f, 
    -0.5f,  0.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.0f,  0.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.5f,  0.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     1.0f,  0.0f,  0.0f,       0.0f,  1.0f,  0.0f,

    -1.0f, -0.5f,  0.0f,       0.0f,  1.0f,  0.0f, 
    -0.5f, -0.5f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.0f, -0.5f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.5f, -0.5f,  0.0f,       0.0f,  1.0f,  0.0f, 
     1.0f, -0.5f,  0.0f,       0.0f,  1.0f,  0.0f, 

    -1.0f, -1.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
    -0.5f, -1.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.0f, -1.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     0.5f, -1.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
     1.0f, -1.0f,  0.0f,       0.0f,  1.0f,  0.0f, 
};

GLuint v_buffer_object, v_array_object, e_buffer_object;
glGenVertexArrays(1, &v_array_object);
glGenBuffers(1, &v_buffer_object);
glGenBuffers(1, &e_buffer_object);

glBindVertexArray(v_array_object);

glBindBuffer(GL_ARRAY_BUFFER, v_buffer_object);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, e_buffer_object);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(grid.Indicies()) * grid.IndiciesSize(), grid.Indicies(), GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0);

glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glEnableVertexAttribArray(1);

glBindBuffer(GL_ARRAY_BUFFER, 0);

glBindVertexArray(0);

glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

Answer 1

不要使用 GL_TRIANGLE_STRIP。使用 GL_TRIANGLES 并使用 2 个三角形和 4 个顶点绘制每个 block 。每个顶点只属于 1 个 block 。由于这一点，您不必使用“平面”标志，只需一次更改 4 个顶点的颜色。您可以尝试将每个 block 分开绘制，彼此之间留有空间。然后您可以通过平移顶点连接它们并创建网格。