Question

在经历了许多痛苦的时间试图弄清楚为什么我的灯光搞砸后，我仍然不知所措。

OpenGL法线是正确的（背面剔除不会导致我的任何三角形消失）

我计算法线以便为光照插值，同一面上的所有三角形也具有相同的法线。

如果有任何人有任何可以理解的想法。

我绝对是OpenGL的新手，所以在我的代码中有点明显。 incorrect lighting

这是我的着色器：

顶点着色器

#version 330 core

layout(location = 0) in vec3 Position;
layout(location = 1) in vec3 vertexColor;
in   vec3 vNormal;

out vec3 fragmentColor; // Output data ; will be interpolated for each fragment.
uniform mat4 MVP;
uniform mat4 transformMatrix;
uniform vec4 LightPosition;

// output values that will be interpretated per-fragment
out  vec3 fN;
out  vec3 fE;
out  vec3 fL;

void main()
{


    fN = vNormal;
    fE = Position.xyz;
    fL = LightPosition.xyz;

    if( LightPosition.w != 0.0 ) {
        fL = LightPosition.xyz - Position.xyz;
    }



    // Output position of the vertex, in clip space : MVP * position
    vec4 v = vec4(Position,1); // Transform in homoneneous 4D vector
    gl_Position = MVP * v;
    //gl_Position = MVP * v;



    // The color of each vertex will be interpolated
    // to produce the color of each fragment
    //fragmentColor = vertexColor; // take out at some point
}

和fragmentShader，使用phong着色

#version 330
//out vec3 color;

// per-fragment interpolated values from the vertex shader
in  vec3 fN;
in  vec3 fL;
in  vec3 fE;

out vec4 fColor;

uniform vec4 AmbientProduct, DiffuseProduct, SpecularProduct;
uniform mat4 ModelView;
uniform vec4 LightPosition;
uniform float Shininess;

in vec3 fragmentColor; // Interpolated values from the vertex shaders

void main()
{

    // Normalize the input lighting vectors
    vec3 N = normalize(fN);
    vec3 E = normalize(fE);
    vec3 L = normalize(fL);

    vec3 H = normalize( L + E );

    vec4 ambient = AmbientProduct;

    float Kd = max(dot(L, N), 0.0);
    vec4 diffuse = Kd*DiffuseProduct;

    float Ks = pow(max(dot(N, H), 0.0), Shininess);
    vec4 specular = Ks*SpecularProduct;

    // discard the specular highlight if the light's behind the vertex
    if( dot(L, N) < 0.0 ) {
    specular = vec4(0.0, 0.0, 0.0, 1.0);
    }

    fColor = ambient + diffuse + specular;
    fColor.a = 1.0;

    //color = vec3(1,0,0);

    // Output color = color specified in the vertex shader,
    // interpolated between all 3 surrounding vertices
    //color = fragmentColor;
}


void setMatrices()
{
    GLfloat FoV = 45; // the zoom of the camera 

    glm::vec3 cameraPosition(4,3,3), // the position of your camera, in world space // change to see what happends
    cameraTarget(0,0,0),         // where you want to look at, in world space
    upVector(0,-1,0);

    // Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
    glm::mat4 Projection = glm::perspective(FoV, 3.0f / 3.0f, 0.001f, 100.0f); // ratio needs to change here when the screen size/ratio changes

    // Camera matrix
    glm::mat4 View = glm::lookAt(
        cameraPosition, // Camera is at (4,3,3), in World Space
        cameraTarget, // and looks at the origin
        upVector  // Head is up (set to 0,-1,0 to look upside-down)
    );

    // Model matrix : an identity matrix (model will be at the origin)
    glm::mat4 Model = glm::mat4(1.0f);  // Changes for each model !

    // Our ModelViewProjection : multiplication of our 3 matrices
    glm::mat4 MVP = Projection * View * Model * transformMatrix; //matrix multiplication is the other way around


    // Get a handle for our "MVP" uniform.
    // Only at initialisation time.
    GLuint MatrixID = glGetUniformLocation(programID, "MVP");
    // Send our transformation to the currently bound shader,
    // in the "MVP" uniform
    // For each model you render, since the MVP will be different (at least the M part)
    glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

    RotationID = glGetUniformLocation(programID,"transformMatrix");

    //lighting
    cubeNormal = glGetAttribLocation( programID, "vNormal" );


}
void setBuffers()
{
    // Get a vertex array object
    GLuint VAO;
    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    glUseProgram(programID);

    // cube buffer objects
    glGenBuffers(1, &CubeVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, CubeVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(CubeBufferData), CubeBufferData, GL_STATIC_DRAW); // Give our vertices to OpenGL.

    // cube normal objects
    glGenBuffers(1, &CubeNormalbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, CubeNormalbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(CubeNormalBufferData), CubeNormalBufferData, GL_STATIC_DRAW); // Give our vertices to OpenGL.




    //octahedron buffer objects
    glGenBuffers(1, &OctaVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, OctaVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(octahedronBufData), octahedronBufData, GL_STATIC_DRAW); // Give our vertices to OpenGL.

    //tetrahedron buffer objects
    glGenBuffers(1, &TetraVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, TetraVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(tetrahedronBufData), tetrahedronBufData, GL_STATIC_DRAW); // Give our vertices to OpenGL.

    //dodecahedron buffer objects
    glGenBuffers(1, &DodecaVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, DodecaVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(dodecahedronBufData), dodecahedronBufData, GL_STATIC_DRAW); // Give our vertices to OpenGL.

    //icosahedron buffer objects
    glGenBuffers(1, &icosaVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, icosaVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(icosahedronBufData), icosahedronBufData, GL_STATIC_DRAW); // Give our vertices to OpenGL.

    //sphere buffer objects
    glGenBuffers(1, &sphereVertexbuffer); // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glBindBuffer(GL_ARRAY_BUFFER, sphereVertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer
    glBufferData(GL_ARRAY_BUFFER, sizeof(sphereBufData), sphereBufData, GL_STATIC_DRAW); // Give our vertices to OpenGL.


    glGenBuffers(1, &colorbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

    // lighting stuff



    // Initialize shader lighting parameters
    point4 light_position= { 0.0, 20.0, -10.0, 0.0 };
    color4 light_ambient ={ 0.2, 0.2, 0.2, 1.0 };
    color4 light_diffuse ={ 1.0, 1.0, 1.0, 1.0 };
    color4 light_specular ={ 1.0, 1.0, 1.0, 1.0 };

    color4 material_ambient ={ 1.0, 0.0, 1.0, 1.0 };
    color4 material_diffuse ={ 1.0, 0.8, 0.0, 1.0 };
    color4 material_specular ={ 1.0, 0.8, 0.0, 1.0 };
    float  material_shininess = 20.0;

    color4 ambient_product;
    color4 diffuse_product;
    color4 specular_product;
    int i;
    for (i = 0; i < 3; i++) {
        ambient_product[i] = light_ambient[i] * material_ambient[i];
        diffuse_product[i] = light_diffuse[i] * material_diffuse[i];
        specular_product[i] = light_specular[i] * material_specular[i];
    }
    //printColor("diffuse", diffuse_product);
    //printColor("specular", specular_product);

    glUniform4fv( glGetUniformLocation(programID, "AmbientProduct"),
      1, ambient_product );
    glUniform4fv( glGetUniformLocation(programID, "DiffuseProduct"),
      1, diffuse_product );
    glUniform4fv( glGetUniformLocation(programID, "SpecularProduct"),
      1, specular_product );

    glUniform4fv( glGetUniformLocation(programID, "LightPosition"),
      1, light_position );

    glUniform1f( glGetUniformLocation(programID, "Shininess"),
     material_shininess );

}

还有一些......

void display()
{

    setMatrices(); // initilize Matrices
    // Use our shader
    //glUseProgram(programID);

    glClearColor(0.0f, 0.0f, 0.3f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 


    // 2nd attribute buffer : colors
    glEnableVertexAttribArray(1);
    glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
    glVertexAttribPointer(
        1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
        3,                                // size
        GL_FLOAT,                         // type
        GL_FALSE,                         // normalized?
        0,                                // stride
        (void*)0                          // array buffer offset
    );

    glEnableVertexAttribArray(0); // 1rst attribute buffer : vertices   

    // enum platosShapes{tet, cube, octah, dodec, icos};
    switch(shapeInUse)
    {
        case tet:
            {

                glBindBuffer(GL_ARRAY_BUFFER, TetraVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );

                glDrawArrays(GL_TRIANGLES, 0, 4*3); // Starting from vertex 0; 3 vertices total -> 1 triangle // need to know amount of vertices here // and change to triangle strips accordingly
            }
            break;
        case cube:
            {

                //GLuint cubeNormal = glGetAttribLocation( programID, "vNormal" ); 
                glEnableVertexAttribArray( cubeNormal );
                glVertexAttribPointer( cubeNormal, 3, GL_FLOAT, GL_FALSE, 0,
                (const GLvoid *) (sizeof(CubeNormalBufferData)) );
                //glDisableVertexAttribArray( cubeNormal );



                glBindBuffer(GL_ARRAY_BUFFER, CubeVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );

                glDrawArrays(GL_TRIANGLES, 0, 12*3); // Starting from vertex 0; 3 vertices total -> 1 triangle // need to know amount of vertices here // and change to triangle strips accordingly
            }
            break;
        case octah:
            {
                glBindBuffer(GL_ARRAY_BUFFER, OctaVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );

                glDrawArrays(GL_TRIANGLES, 0, 8*3); // Starting from vertex 0; 3 vertices total -> 1 triangle // need to know amount of vertices here // and change to triangle strips accordingly
            }
            break;
        case dodec:
            {
                glBindBuffer(GL_ARRAY_BUFFER, DodecaVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );

                glDrawArrays(GL_TRIANGLE_FAN, 0, 5 * 6); // Starting from vertex 0; 3 vertices total -> 1 triangle // need to know amount of vertices here // and change to triangle strips accordingly
                glDrawArrays(GL_TRIANGLE_FAN, (5 * 6) + 1, 30);
                //glutSolidDodecahedron();
                //glDrawArrays(GL_TRIANGLE_STRIP,0,5*12);
            }
            break;
        case icos:
            {
                glBindBuffer(GL_ARRAY_BUFFER, icosaVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );

                glDrawArrays(GL_TRIANGLES, 0, 3*20); // Starting from vertex 0; 3 vertices total -> 1 triangle // need to know amount of vertices here // and change to triangle strips accordingly
            }
            break;
        case sphere:
            {
                glBindBuffer(GL_ARRAY_BUFFER, sphereVertexbuffer);
                glVertexAttribPointer(
                    0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
                    3,                  // size
                    GL_FLOAT,           // type
                    GL_FALSE,           // normalized?
                    0,                  // stride
                    (void*)0            // array buffer offset
                );
                //glDrawElements(GL_TRIANGLES, cnt2, GL_UNSIGNED_INT, 0)
                glDrawArrays(GL_TRIANGLE_FAN, 0, 100);
            }
    }

    glDisableVertexAttribArray(0);
    glFlush();

}

还有一些........

void calculateNormals(GLfloat bufData[], GLfloat normBufData[], int size) // probalby works
{
    int count = 0;
    GLfloat temp[9];

    for(int i = 0; i < size; i++)
    {

        temp[count] = bufData[i];
        count++;

        if((i+1) % 9 == 0)
        {
            count = 0;

            //for(int i = 0; i < 9; i++)
            //{
            //  cout << temp[i] << "!,";
            //  if((i + 1) % 3 == 0)
            //      cout << "\n";
            //}

            calculateCross(temp, normBufData);
        }
    }

    printNormals(normBufData, size);
}
void calculateCross(GLfloat bufData[], GLfloat normBufData[]) // probably works
{
    static int counter = 0; // need to reset in bettween new buffers

    glm::vec3 C1;
    glm::vec3 C2;
    glm::vec3 normal;

    //cout << bufData[0] << "," << bufData[1] << "," << bufData[2] << " buf 1 \n"; 
    //cout << bufData[3] << "," << bufData[4] << "," << bufData[5] << " buf 2 \n"; 
    //cout << bufData[6] << "," << bufData[7] << "," << bufData[8] << " buf 3 \n\n"; 



    //C1.x = bufData[3] - bufData[0];
    //C1.y = bufData[4] - bufData[1];
    //C1.z = bufData[5] - bufData[2];

    //C2.x = bufData[6] - bufData[0];
    //C2.y = bufData[7] - bufData[1];
    //C2.z = bufData[8] - bufData[2];

    C1.x = bufData[0] - bufData[3];
    C1.y = bufData[1] - bufData[4];
    C1.z = bufData[2] - bufData[5];

    C2.x = bufData[0] - bufData[6];
    C2.y = bufData[1] - bufData[7];
    C2.z = bufData[2] - bufData[8];

    //C2.x = bufData[6] - bufData[0];
    //C2.y = bufData[7] - bufData[1];
    //C2.z = bufData[8] - bufData[2];

    //cout << C1.x << " 1x \n";
    //cout << C1.y << " 1y \n";
    //cout << C1.z << " 1z \n";

    //cout << C2.x << " 2x \n";
    //cout << C2.y << " 2y \n";
    //cout << C2.z << " 2z \n";

    normal = glm::cross(C1, C2);

    //cout << "\nNORMAL : " << normal.x << "," << normal.y << "," << normal.z << " counter = " << counter << "\n";

    for(int j = 0; j < 3; j++)
    {
        for(int i = 0; i < 3; i++)
        {
            normBufData[counter] = normal.x;
            normBufData[counter + 1] = normal.y;
            normBufData[counter + 2] = normal.z;

        }
        counter+=3;
    }






}

和主要.....

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(700, 700);    // Window Size

    glutCreateWindow("Michael - Lab 3");
    glutDisplayFunc(display);
    glutTimerFunc(10, timeFucn, 10);
    glutIdleFunc(Idle);
    glutKeyboardFunc(keyboard);
    glewExperimental = GL_TRUE;
    glewInit();

    glEnable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST); // Enable depth test
    glDepthFunc(GL_LESS); // Accept fragment if it closer to the camera than the former one

    GenerateSphere(); // this function generates points for the sphere

    programID = LoadShader( "VertexShader.glsl", "FragmentShader.glsl" ); // Create and compile our GLSL program from the shaders

    setBuffers(); // initilize buffers

    calculateNormals(CubeBufferData,CubeNormalBufferData,108); // calculate norms
    //printNormals(CubeNormalBufferData);

    glutMainLoop();
}

Answer 1

在调用glVertexAttribPointer( cubeNormal, 3,....);之前，您忘记将缓冲区对象与法线绑定。因此，法线的实际数据来自颜色缓冲区，这会导致最奇怪的Phong评估结果。

BTW，编码风格很好：）

Answer 2

Phong和Gouraud阴影不适用于具有所有平面表面的物体，例如：一个立方体。

使用phong着色打乱了OpenGL 3.1灯光

2 个答案: