c++ - GLSL 4.5 : Why is my "in" variable for Color Not Being Found by glGetAttribLocation

Question

这是顶点着色器

#version 450

in vec3 iPosition;
in vec4 iColor;

out vec4 oColor;

uniform mat4 uMVP;

void main()
{
  oColor = iColor;
  gl_Position = uMVP * vec4(iPosition, 1.0);
}

这是片段着色器

#version 450

in vec4 iColor;

out vec4 oColor;

void main()
{
  oColor = iColor;
}

除了粘贴我所有的代码，这是我所做的:

1. 1) 每次调用 Open GL 函数调用后，我都会遇到 glGetError。在对顶点着色器中的 iColor 变量调用 glGetAttribLocation 之前，我没有收到任何错误。

2. 在分别调用 glCompileShader 和 glLinkProgram 之后，我有以下代码:

---

GLint isCompiled = 0;
glGetShaderiv(m_fragmentShader, GL_COMPILE_STATUS, &isCompiled); GL_CALL
if(isCompiled == GL_FALSE) {
  GLint maxLength = 0;
  glGetShaderiv(m_fragmentShader, GL_INFO_LOG_LENGTH, &maxLength); GL_CALL
  std::vector<GLchar> errorLog(maxLength);
  glGetShaderInfoLog(m_fragmentShader, maxLength, &maxLength, &errorLog[0]);
  GL_CALL
  std::stringstream out;
  std::copy(errorLog.begin(), errorLog.end(), std::ostream_iterator<char>(
    out, ""));
  qDebug() << out.str().c_str();
  glDeleteShader(m_fragmentShader); GL_CALL
  QCoreApplication::exit(-1);
}

---

 GLint isLinked = 0;
 glGetProgramiv(m_shaderProgram, GL_LINK_STATUS, (int *)&isLinked);
 if(isLinked == GL_FALSE) {
   GLint maxLength = 0;
   glGetProgramiv(m_shaderProgram, GL_INFO_LOG_LENGTH, &maxLength); GL_CALL
   std::vector<GLchar> infoLog(maxLength);
   glGetProgramInfoLog(m_shaderProgram, maxLength, &maxLength, &infoLog[0]);
   GL_CALL
   std::stringstream out;
   std::copy(infoLog.begin(), infoLog.end(), std::ostream_iterator<char>(
     out, ""));
   qDebug() << out.str().c_str();
   glDeleteProgram(m_shaderProgram); GL_CALL
   glDeleteShader(m_vertexShader); GL_CALL
   glDeleteShader(m_fragmentShader); GL_CALL
   QCoreApplication::exit(-1);
 }

1. 我已尝试将版本改回 150，但出现同样的错误。我知道有些实现会优化变量。但是我明明是用这个来判断颜色的。

2. 我打算返回版本控制历史，看看是什么变化导致了这个错误，但这可能需要我一些时间。

如果有帮助，这里是绘制函数的简化版本:

void Spline::draw()                          
{ 
  glUseProgram(m_shaderProgram); GL_CALL     

  GLint posAttrib = glGetAttribLocation(m_shaderProgram, "iPosition"); GL_CALL
  GLint colAttrib = glGetAttribLocation(m_shaderProgram, "iColor"); GL_CALL

  glBindBuffer(GL_ARRAY_BUFFER, m_vbo); GL_CALL 
  std::size_t stride = verts::traits::stride;

  std::size_t dimension1 = verts::datum_type::internal_type1::dimension; 
  std::size_t byte_offset1 = verts::traits::type1_byte_offset;
  glEnableVertexAttribArray(posAttrib); GL_CALL 
  glVertexAttribPointer(posAttrib, dimension1, GL_FLOAT, GL_FALSE,
    stride, (void*)byte_offset1); GL_CALL    

  std::size_t dimension2 = verts::datum_type::internal_type2::dimension; 
  std::size_t byte_offset2 = verts::traits::type2_byte_offset;
  glEnableVertexAttribArray(colAttrib); GL_CALL 
  glVertexAttribPointer(colAttrib, dimension2, GL_FLOAT, GL_FALSE,
    stride, (void*)byte_offset2); GL_CALL    

  opengl_math::matrix_4X4<float, opengl_math::column> model(
    opengl_math::identity);                  
  opengl_math::matrix_4X4<float, opengl_math::column> view =
    opengl_math::look_at<float, opengl_math::column>(
      opengl_math::point_3d<float>(0.0f, 0.0f, 20.0f),
      opengl_math::point_3d<float>(0.0f, 0.0f, 0.0f),
      opengl_math::vector_3d<float>(0.0f, 1.0f, 0.0f));

  GLint uniMVP = glGetUniformLocation(m_shaderProgram, "uMVP"); GL_CALL
  glUniformMatrix4fv(uniMVP, 1, GL_FALSE,    
    (m_projection * view * model).to_gl_matrix()); GL_CALL

  glDrawArrays(GL_LINE_STRIP, 0, m_vertexAttrib.get_attribute_count());
  GL_CALL
}

Answer 1

您在两个着色器阶段都使用 iColor 作为输入名称。由于无法查询片段着色器属性，因此您必须确保该名称在着色器中是唯一的。您可以使用以下代码执行此操作:

顶点:

#version 450

in vec3 iPosition;
in vec4 iColor;

out vec4 xColor;

uniform mat4 uMVP;

void main()
{
    xColor = iColor;
    gl_Position = uMVP * vec4(iPosition, 1.0);
}

片段:

#version 450

in vec4 xColor;

out vec4 oColor;

void main()
{
    oColor = xColor;
}