我在着色器中的照明功能有什么问题?

What's wrong with my lighting function in the shader?

我正在努力寻找我的顶点着色器中超简单光照函数的错误:

in vec4 position;           /* Homogenized input vertex position.           */
in vec4 color;              /* Input color information.                     */
in vec3 normal;             /* Normal vector to the surface.                */

uniform mat4 ortho;         /* Orthographic matrix.         */
uniform mat4 model;         /* Modelling matrix.            */
uniform mat4 view;          /* View transformation.         */
uniform mat4 project;       /* Projection matrix.           */

out vec4 color_out;         /* Color passed to the fragment shader. */

float light()
{
    mat3 normat = transpose(inverse(mat3(view * model)));
    vec3 norm  = normalize(normat * normalize(normal));
    vec3 light = normalize(vec3(1.0f, 1.0f, 1.0f));
    return max(dot(norm, light), 0.0f);
}
void main()
{
    gl_Position = ortho * project * view * model * position;
    color_out = vec4(color.rgb * light(), color.a);
}

此函数用于照亮旋转的 icosphere 的表面。因为我已经手动生成了 icosphere 的顶点并且我可以随时访问它们,所以我尝试在 CPU 代码中复制相同的操作来显示一张脸的结果,例如:

Normal Matrix:                 Normal vectors for face 10:
 [ 0.08     0.59    -0.81]     { 3936}[-0.58     0.61    -0.54] --> light: 0.694
 [-0.00     0.81     0.59]     { 3937}[-0.58     0.61    -0.54] --> light: 0.694
 [ 1.00    -0.04     0.06]     { 3938}[-0.58     0.61    -0.54] --> light: 0.694

无论法向量是否正确,光值确实会随着球体的旋转而变化。但是,如果我 运行 代码(并让着色器计算值),生成的三角形面会完全变暗。

这是我将顶点数据复制到缓冲区以及指向属性的方式:

/* (...) Bind shader, and get attribute locations. */
/* (...) Create VBO. */
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(Vertex), vertices.data(), GL_DYNAMIC_DRAW);
/* (...) */

glVertexAttribPointer(position_id, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(color_id,    4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void *)sizeof(glm::vec3));
glVertexAttribPointer(normal_id,   3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void *)(sizeof(glm::vec3) + sizeof(glm::vec4)));

/* For reference: vertices is a std::vector<Vertex>, where Vertex 
 * is defined as: 
 *
 * struct Vertex {
 *     glm::vec3 p; ---> Position. 
 *     glm::vec4 c; ---> Color.    
 *     glm::vec3 n; ---> Normal.   
 * };
 **/

愚蠢的我,我忘了启用 normal 顶点属性...这是我缺少的行:

glEnableVertexAttribArray(normal_id);

其中 normal_id 之前已与 glGetAttribLocation 绑定。