打开GL ES，多个着色器

Question

我很好奇你是否可以在Open GL ES 2.0程序中拥有多个着色器。

这是着色器的代码。 但是，属性和制服只能从rigid.vert和rigid.frag着色器中检索变量：

- (BOOL)loadShaders
{
GLuint rigidVertShader, rigidFragShader, skinningVertShader, skinningFragShader;
NSString *rigidVertShaderPathname, *rigidFragShaderPathname, *skinningVertShaderPathname, *skinningFragShaderPathname;

// Create shader program.
_program = glCreateProgram();

// Create and compile rigid vertex shader.
rigidVertShaderPathname = [[NSBundle mainBundle] pathForResource:@"rigid" ofType:@"vert"];
if (![self compileShader:&rigidVertShader type:GL_VERTEX_SHADER file:rigidVertShaderPathname]) {
    NSLog(@"Failed to compile rigid vertex shader");
    return NO;
}

// Create and compile rigid fragment shader.
rigidFragShaderPathname = [[NSBundle mainBundle] pathForResource:@"rigid" ofType:@"frag"];
if (![self compileShader:&rigidFragShader type:GL_FRAGMENT_SHADER file:rigidFragShaderPathname]) {
    NSLog(@"Failed to compile rigid fragment shader");
    return NO;
}

// Create and compile skinning vertex shader.
skinningVertShaderPathname = [[NSBundle mainBundle] pathForResource:@"skinning" ofType:@"vert"];
if (![self compileShader:&skinningVertShader type:GL_VERTEX_SHADER file:skinningVertShaderPathname]) {
    NSLog(@"Failed to compile skinning vertex shader");
    return NO;
}

// Create and compile skinning fragment shader.
skinningFragShaderPathname = [[NSBundle mainBundle] pathForResource:@"skinning" ofType:@"frag"];
if (![self compileShader:&skinningFragShader type:GL_FRAGMENT_SHADER file:skinningFragShaderPathname]) {
    NSLog(@"Failed to compile skinning fragment shader");
    return NO;
}

// Attach rigid vertex shader to program.
glAttachShader(_program, rigidVertShader);

// Attach rigid fragment shader to program.
glAttachShader(_program, rigidFragShader);

// Attach skinning vertex shader to program.
glAttachShader(_program, skinningVertShader);

// Attach skinning fragment shader to program.
glAttachShader(_program, skinningFragShader);

// Link program.
if (![self linkProgram:_program]) {
    NSLog(@"Failed to link program: %d", _program);

    if (rigidVertShader) {
        glDeleteShader(rigidVertShader);
        rigidVertShader = 0;
    }
    if (rigidFragShader) {
        glDeleteShader(rigidFragShader);
        rigidFragShader = 0;
    }
    if (skinningVertShader) {
        glDeleteShader(skinningVertShader);
        skinningVertShader = 0;
    }
    if (skinningFragShader) {
        glDeleteShader(skinningFragShader);
        skinningFragShader = 0;
    }
    if (_program) {
        glDeleteProgram(_program);
        _program = 0;
    }

    return NO;
}

// GET UNIFORM LOCATIONS
// Dictionary to store each active uniform
NSMutableDictionary *m_uniforms = [[NSMutableDictionary alloc] init];
int m_nUniforms = -1;
glGetProgramiv( _program, GL_ACTIVE_UNIFORMS, &m_nUniforms );

for(GLuint i = 0; i < m_nUniforms; i++)  {
    int name_len=-1, num=-1;
    GLenum type = GL_ZERO;
    char uniformName[100];

    glGetActiveUniform( _program, i, sizeof(uniformName)-1, &name_len, &num, &type, uniformName );

    uniformName[name_len] = 0;

    GLuint uniform = glGetUniformLocation( _program, uniformName );

    [m_uniforms setObject:[NSNumber numberWithUnsignedInt:uniform]
                   forKey:[NSString stringWithUTF8String:uniformName]];    
}

// GET ATTRIBUTE LOCATIONS
// Dictionary to store each active attribute
NSMutableDictionary *m_attributes = [[NSMutableDictionary alloc] init];
int m_nAttributes = -1;
glGetProgramiv( _program, GL_ACTIVE_ATTRIBUTES, &m_nAttributes );

for(GLuint i = 0; i < m_nAttributes; i++)  {
    int name_len=-1, num=-1;
    GLenum type = GL_ZERO;
    char attributesName[100];

    glGetActiveAttrib( _program, i, sizeof(attributesName)-1, &name_len, &num, &type, attributesName );

    attributesName[name_len] = 0;

    GLuint attributes = glGetAttribLocation( _program, attributesName );

    [m_attributes setObject:[NSNumber numberWithUnsignedInt:attributes]
                     forKey:[NSString stringWithUTF8String:attributesName]];
}


// Release vertex and fragment shaders.
if (rigidVertShader) {
    glDetachShader(_program, rigidVertShader);
    glDeleteShader(rigidVertShader);
}
if (rigidFragShader) {
    glDetachShader(_program, rigidFragShader);
    glDeleteShader(rigidFragShader);
}
if (skinningVertShader) {
    glDetachShader(_program, skinningVertShader);
    glDeleteShader(skinningVertShader);
}
if (skinningFragShader) {
    glDetachShader(_program, skinningFragShader);
    glDeleteShader(skinningFragShader);
}

return YES;
}

Answer 1

OpenGL ES不允许在程序中使用相同类型的多个着色器，这与“桌面”OpenGL不同 （但它只允许您声明常用函数/变量，因此它与连接着色器源大致相同）。 来自glAttachShader（）规范 ：

可能无法将多个相同类型的着色器对象附加到单个程序对象。

...

错误

... GL_INVALID_OPERATION如果相同类型的着色器的另一个对象的着色器已附加到程序如果着色器已附加到程序生成，或。

我强烈怀疑对glAttachShader()的第三次和第四次调用设置了GL_INVALID_OPERATION 。

检查你的错误！ 我在循环中调用glGetError() ，直到它返回GL_NO_ERROR 。

Answer 2

在OpenGL ES中，每个着色器程序只能使用一个片段和一个顶点着色器。 否则它就行不通。