使用phong陰影使OpenGL 3.1照明混亂

Question

在經過數小時的痛苦嘗試來弄清楚為什么我的燈光混亂之后，我仍然茫然。

OpenGL法線是正確的（背面剔除不會導致我的三角形消失）

我計算法線以進行照明插值，同一面上的所有三角形也具有相同的法線。

如果有人有任何想法，將不勝感激。

我絕對不熟悉OpenGL，因此在我的代碼中這很明顯。

這是我的着色器：

• 頂點着色器

   #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 ); } 

還有更多...

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();

}

還有一些........

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

您忘記了在調用glVertexAttribPointer( cubeNormal, 3,....);之前將緩沖區對象與法線綁定glVertexAttribPointer( cubeNormal, 3,....); 。 因此，法線的實際數據來自顏色緩沖區，這導致最奇怪的Phong評估結果。

順便說一句，不錯的編碼風格:)

Answer 2

Phong和Gouraud陰影不適用於具有所有平面表面的物體，例如立方體。