glGetUniformLocation（）返回-1即使在顶点着色器中使用 [英] glGetUniformLocation() returning -1 even though used in vertex shader

问题描述

我试图渲染一个简单的多维数据集与法线。我使用下面的代码来初始化着色器。

  void initShader（const char * vertexShaderPath，const char * fragmentShaderPath）{
 cout& <<< endl<<===<< endl; 
 cout<<Vertex shader; 
 vs = loadShader（vertexShaderPath，GL_VERTEX_SHADER）; 
 cout<<Fragment shader; 
 fs = loadShader（fragmentShaderPath，GL_FRAGMENT_SHADER）; 
 
 cout<<Creating program：; 
 program = glCreateProgram（）; 
 if（0 == program）cout<< Failed<< endl; else cout< OK<< endl; 
 
 glAttachShader（program，vs）; 
 glAttachShader（program，fs）; 
 
 cout<<链接程序：; 
 glLinkProgram（program）; 
 GLint linkstatus = 0; 
 glGetProgramiv（program，GL_LINK_STATUS，& linkstatus）; 
 if（GL_TRUE == linkstatus）cout<<OK<< endl; else cout<<Failed<< endl; 
 
 cout << endl<< endl<<Memory status<<< endl<<===< 
 
 mvpmat = glGetUniformLocation（program，mvpMatrix）; 
 mvmat = glGetUniformLocation（program，mvMatrix）; 
 normalmat = glGetUniformLocation（program，normalMatrix）; 
 
 cout<< mvpMatrix：<< mvpmat<<mvMatrix：<< mvmat<<normalMatrix：< normalmat<<< 
} 
  

最后一个cout语句的输出如下所示编译或链接）。

  mvpMatrix：0 mvMatrix：-1 normalMatrix：1 
  
 
 
 
这是我的顶点着色器代码
  uniform mat4 mvpMatrix; 
 uniform mat4 mvMatrix; 
 uniform mat3 normalMatrix; 
 attribute vec3 vertex; 
 attribute vec3 normal; 
 changing vec3 outNormal; 
 varying vec3 outPos; 
 
 void main（）{
 gl_Position = mvpMatrix * vec4（vertex，1.0）; 
 outPos =（mvMatrix * vec4（vertex，1.0））。xyz; 
 outNormal = normalize（normalMatrix * normal）; 
} 
  
 
 
我在代码中使用了所有mvpMatrix，mvMatrix和normalMatrix。因此，我真的很困惑为什么getUniformLocation（）返回mvMatrix = -1？
解决方案
如果你的片段着色器不使用outPos的输入将被优化掉。制服定义为后链接。因此片元和顶点着色器计数。
 
I'm trying to render a simple cube with normals. I'm using the following code to initialize the shaders. 
void initShader(const char* vertexShaderPath, const char* fragmentShaderPath){
    cout<<"Initializing Shaders"<<endl<<"==="<<endl;
    cout<<"Vertex shader ";
    vs = loadShader(vertexShaderPath, GL_VERTEX_SHADER);
    cout<<"Fragment shader ";
    fs = loadShader(fragmentShaderPath, GL_FRAGMENT_SHADER);

    cout<<"Creating program: ";
    program = glCreateProgram();
    if(0==program) cout<< "Failed"<<endl; else cout<< "OK"<<endl;

    glAttachShader(program, vs);
    glAttachShader(program, fs);

    cout<<"Linking program: ";
    glLinkProgram(program); 
    GLint linkstatus = 0;
    glGetProgramiv(program, GL_LINK_STATUS, &linkstatus);
    if(GL_TRUE==linkstatus) cout<<"OK"<<endl; else cout<<"Failed" <<endl;

    cout<<endl<<endl<<"Memory status"<<endl<<"==="<<endl;

    mvpmat = glGetUniformLocation(program,"mvpMatrix");
    mvmat = glGetUniformLocation(program,"mvMatrix");
    normalmat = glGetUniformLocation(program,"normalMatrix");

    cout << "mvpMatrix: "<<mvpmat<<" mvMatrix: "<<mvmat<<" normalMatrix: " << normalmat<<endl;
}
The output of the last cout statement appears as follows (There is no error during compilation or linking).
mvpMatrix: 0 mvMatrix: -1 normalMatrix: 1
This is my vertex shader code
uniform mat4 mvpMatrix;
uniform mat4 mvMatrix;
uniform mat3 normalMatrix;
attribute vec3 vertex;
attribute vec3 normal;
varying vec3 outNormal;
varying vec3 outPos;

void main(){
    gl_Position = mvpMatrix*vec4(vertex,1.0);
    outPos = (mvMatrix*vec4(vertex,1.0)).xyz;
    outNormal = normalize(normalMatrix*normal);
}
I've used all mvpMatrix, mvMatrix and normalMatrix in the code. Thus i'm really confused why getUniformLocation() is returning mvMatrix = -1?
解决方案
If your fragment shader does not use the input of outPos it will be optimized away. Uniforms are defined post-link. So both fragment and vertex shader count.

                        
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