c++ - 如何在渲染之间更改片段着色器颜色？

Question

我正在努力编写这个简单的船场景。这是一个家庭作业问题，但我真的很难过。我上传了两个模型。一个是立方体，它有一个片段着色器，可以将自身着色为蓝色。第二个是一艘船，它有一个片段着色器，可以将自己着色为白色。当我使用两种不同的着色器时，船模型是不可见的。经过许多挣扎和寻找

我很困惑，所以我正在尝试 B 计划，它找到了一种方法来在渲染两个对象之间更改片段着色器的颜色，但我不知道该怎么做。

void render() {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //BOAT START
    //Rocks the ship, simulating ocean rocking
    if(shiprocker < 5000){
        shiprocker++;
        theta += 0.00002f;
    }
    if(shiprocker ==15000){
        shiprocker = -5000;
    }
    if(shiprocker > 4999){
        shiprocker++;
        theta -= 0.00002f;
    }
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);  

    boat_model->mR = glm::rotate(            
        glm::mat4( 1.0f ),
        glm::degrees( theta ),
        glm::vec3(0.0f, 0.0f, 1.0f)
        );

    glm::mat4 mtx_trans = glm::translate(
        glm::mat4(1.0f),
        glm::vec3( 0.0f, 0.0f, -15.0f )
        );

    boat_model->mM =  mtx_trans * boat_model->mR;        
    boat_model->render();
    //BOAT END


    //OCEAN CUBE START
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);  

    glm::mat4 mtx_trans_cube = glm::translate(
        glm::mat4( 1.0f ),
        glm::vec3( -20.0f, -50.0f, -50.0f ) 
        );

    plane_model->mM = glm::scale(  
        mtx_trans_cube,              
        glm::vec3( 10.0f, 10.0f, 10.0f )
        );

    //gl_FragColor = (0.0f, 0.0f, 1.0f , 1.0f); wont compile
    //glColor3f(0.0f, 0.0f, 1.0f); changes nothing

    camera->set_uniform_view_perspective( plane_model->shader->program_ID );
    plane_model->render();
    //OCEAN CUBE END


    glutSwapBuffers();
}



int main (int argc, char** argv) {

    // Initialize GLUT
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH|GLUT_MULTISAMPLE | GLUT_RGB);


    //WINDOW SETTINGS
    glutInitWindowSize(1000, 1000);
    glutCreateWindow("SailBoat");

    //PASSIVE FUNCS
    glutReshapeFunc(change_viewport);
    glutDisplayFunc(render);
    glutIdleFunc( animate );

    //ERROR CHECK
    if (GLEW_OK != glewInit()) {
        exit(1);
    }

    //Clear color used for sky tones.
    glClearColor(0.529f, 0.807f, .98f, 1.0f);
    glEnable (GL_DEPTH_TEST);
    glEnable (GL_MULTISAMPLE);

    Shader* boatShader = new Shader( VERTEX_SHADER, BOAT_FRAGMENT_SHADER );
    Shader* cubeShader = new Shader( VERTEX_SHADER, CUBE_FRAGMENT_SHADER );

    //BOAT
    boat_model = new Model(boatShader); 
    load_model(boat_model ,MODEL_BOAT_FILENAME);
    boat_model->upload_2_server();


    //OCEAN CUBE
    plane_model = new Model( boatShader );
    load_model(plane_model ,MODEL_PLANE_FILENAME);
    plane_model->upload_2_server();

    // Set up the camera 
    theta = 0.0f;
    shiprocker = 0;
    camera = new FPSCamera(60.0f, 1.0f, 1.0f, 10000.0f, true);
    glutMainLoop();

    return 0;
}

片段着色器

#version 150

in vec4 color;
out vec4 fColor;

void main () {
    fColor = vec4(1.0, 1.0, 1.0, 0.5);

Answer 1

您可以在 GLSL 中使用统一变量在渲染调用之间传递值。像这样设置片段着色器:

#version 150

in vec4 color;
out vec4 fColor;
uniform vec3 boatColor;

void main () {
    fColor = vec4(boatColor, 0.5);
}

在您的 C++ 代码中:

glUseProgram(program); // Where program is your shader program
GLint uniform = glGetUniformLocation(program, "boatColor"); // since boatColor is what we called the uniform variable in our fragment shader
glUniform3f(uniform, 1.0f, 0.0f, 0.0f); // Set the boatColor variable to be a solid red
// Render your first boat
glUniform3f(uniform, 0.0f, 0.0f, 1.0f); // Set the second boat to be a solid blue
// Render your second boat
glUseProgram(0);

这应该会很好地工作。如果这里的其他人有更好的方法，请告诉我；我对 GLSL 比较陌生。