[英]What's wrong with my lighting function in the shader?
我正在努力在我的頂點着色器中找到超簡化照明功能中的錯誤:
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);
}
此功能用於照亮旋轉的icosphere的面。 由於我已經手動生成了icosphere的頂點,並且可以隨時訪問它們,因此我嘗試在CPU代碼中復制相同的操作,以顯示一張臉的結果,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
盡管法向矢量正確與否,但光照值的確會隨着球體旋轉而變化。 但是,如果我運行代碼(並讓着色器計算值),則生成的三角形面將顯示為完全黑暗。
這是將頂點數據復制到緩沖區以及如何指向屬性的方法:
/* (...) 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,我忘了啟用普通頂點屬性...這是我所缺少的行:
glEnableVertexAttribArray(normal_id);
其中normal_id
之前已與glGetAttribLocation
綁定。
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