学习LearnOpenGL第13章后，基于Phong模型得到奇怪的照明结果

yebdmbv4  于 2022-11-23  发布在  其他
关注(0)|答案(1)|浏览(145)

第一个错误结果

大家好，我一直在www.example.com上学习OpenGLlearnopengl.com，当我学习完基础照明章节时，我发现结果很奇怪。结果是我在立方体表面的角上发现了光无法到达的镜面反射光。奇怪的结果如下图所示：


即使摄像机隐藏在立方体后面不受光线影响，奇怪的镜面反射光仍然存在：

我的顶点着色器是：

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

out vec3 FragPos;
out vec3 Normal;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
uniform mat3 normalMatrix;

void main()
{
    FragPos = vec3(model * vec4(aPos, 1.0));
    Normal = normalMatrix * aNormal;
    // Normal = aNormal;

    gl_Position = projection * view * vec4(FragPos, 1.0);
}

我的片段着色器是（与LearnOpenGL提供的官方代码相同）：

#version 330 core
out vec4 FragColor;

in vec3 Normal;  
in vec3 FragPos;  
  
uniform vec3 lightPos; 
uniform vec3 viewPos; 
uniform vec3 lightColor;
uniform vec3 objectColor;

void main()
{
    // ambient
    float ambientStrength = 0.1;
    vec3 ambient = ambientStrength * lightColor;
    
    // diffuse 
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(lightPos - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = diff * lightColor;
    
    // specular
    float specularStrength = 0.5;
    vec3 viewDir = normalize(viewPos - FragPos);
    vec3 reflectDir = reflect(-lightDir, norm);  
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
    vec3 specular = specularStrength * spec * lightColor;  
        
    vec3 result = (ambient + diffuse + specular) * objectColor;
    FragColor = vec4(result, 1.0);
}

我的源文件是：

#include"glm/glm.hpp"
#include"glm/gtc/matrix_transform.hpp"
#include"glm/gtc/type_ptr.hpp"
#include<iostream>
#include"LearnOpenGL/camera.h"
#include "LearnOpenGL/stb_image.h"
#include "glad/glad.h"
#include <GLFW/glfw3.h>
#include"LearnOpenGL/shader_m.h"
#include <cmath>

#define STB_IMAGE_IMPLEMENTATION

void framebuffer_size_callback(GLFWwindow *window, int width, int height);

void processInput(GLFWwindow *window);

void mouse_callback(GLFWwindow *window, double xpos, double ypos);

void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

// camera attributes
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = SCR_WIDTH / 2.0f;
float lastY = SCR_HEIGHT / 2.0f;
bool firstMouse = true;
float fov = 45.0f;

// timing
float deltaTime = 0.0f; // time between current frame and last frame
float lastFrame = 0.0f; // time of last frame

// lighting
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);

int main() {
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

    // glfw window creation
    // --------------------
    GLFWwindow *window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL) {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    // cursor
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    glfwSetCursorPosCallback(window, mouse_callback);
    glfwSetScrollCallback(window, scroll_callback);

    // shader declaration
    Shader ourShader("../src/shaders/shader.vs", "../src/shaders/shader.fs");
    Shader lightingShader("../src/shaders/lightsource_shader.vs", "../src/shaders/lightsource_shader.fs");

    // set up vertex data (and buffer(s)) and configure vertex attributes
    // ------------------------------------------------------------------

    float vertices[] = {
            -0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
            0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
            0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
            0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
            -0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,

            -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,
            0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,
            0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,
            0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,
            -0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,
            -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,

            -0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,
            -0.5f,  0.5f, -0.5f, -1.0f,  0.0f,  0.0f,
            -0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,
            -0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,
            -0.5f, -0.5f,  0.5f, -1.0f,  0.0f,  0.0f,
            -0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,

            0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,
            0.5f,  0.5f, -0.5f,  1.0f,  0.0f,  0.0f,
            0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,
            0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,
            0.5f, -0.5f,  0.5f,  1.0f,  0.0f,  0.0f,
            0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,

            -0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,
            0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,
            0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,
            0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,

            -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,
            0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,
            0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
            0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
            -0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
            -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f
    };

    // first, configure the cube's VAO (and VBO)
    unsigned int VBO, cubeVAO;
    glGenVertexArrays(1, &cubeVAO);
    glGenBuffers(1, &VBO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glBindVertexArray(cubeVAO);

    // position attribute
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *) 0);
    glEnableVertexAttribArray(0);

    // normal attribute 
    glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float),(void*)0);
    glEnableVertexAttribArray(1);

    //second, configure the light's VAO (VBO stays the same; the vertices are the same for the light object which is also a 3D cube)
    unsigned int lightCubeVAO;
    glGenVertexArrays(1, &lightCubeVAO);
    glBindVertexArray(lightCubeVAO);

    // we only need to bind to the VBo (to link it with glVertexAtrribPointer), no need to fill it; the VBO's data already contains all we need (it's already bound, but we do it again for educational purposes)
    glBindBuffer(GL_ARRAY_BUFFER, VBO);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *) 0);
    glEnableVertexAttribArray(0);

    glEnable(GL_DEPTH_TEST);

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window)) {

        // per-frame time logic
        // --------------------
        float currentFrame = static_cast<float>(glfwGetTime());
        deltaTime = glfwGetTime() - lastFrame;
        lastFrame = glfwGetTime();

        // input
        // -----
        processInput(window);

        // render
        // ------

        // firstly clear the screen
        glClearColor(0.1f, 0.1f, 0.1f, 0.1f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // activate shader
        ourShader.use();
        ourShader.setVec3("objectColor", 1.0f, 0.5f, 0.31f);
        ourShader.setVec3("lightColor", 1.0f, 1.0f, 1.0f);
        ourShader.setVec3("lightPos", lightPos);
        ourShader.setVec3("viewPos", camera.Position);

        // view/projection transformations
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float) SCR_WIDTH / (float) SCR_HEIGHT, 0.1f,100.0f);
        glm::mat4 view = camera.GetViewMatrix();
        ourShader.setMat4("projection", projection);
        ourShader.setMat4("view", view);

        // model transformation (aka world transformation)
        glm::mat4 model = glm::mat4(1.0f);
        ourShader.setMat4("model", model);
        glm::mat3 normal_matrix = glm::transpose(glm::inverse(glm::mat3(model)));
        // glm::mat3 normal_matrix = glm::mat3(glm::transpose(glm::inverse(model)));
        ourShader.setMat3("normalMatrix", normal_matrix);

        // render the cube
        glBindVertexArray(cubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

        // also draw the lamp object
        lightingShader.use();
        lightingShader.setMat4("projection", projection);
        lightingShader.setMat4("view", view);
        model = glm::mat4(1.0f);
        model = glm::translate(model, lightPos);
        model = glm::scale(model, glm::vec3(0.1f));
        lightingShader.setMat4("model", model);
        glBindVertexArray(cubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);


        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // optional: de-allocate all resources once they've outlived their purpose:
    // ------------------------------------------------------------------------
    glDeleteVertexArrays(1, &cubeVAO);
    glDeleteVertexArrays(1, &lightCubeVAO);
    glDeleteBuffers(1, &VBO);

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window) {
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);

    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
        camera.ProcessKeyboard(FORWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
        camera.ProcessKeyboard(BACKWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
        camera.ProcessKeyboard(LEFT, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
        camera.ProcessKeyboard(RIGHT, deltaTime);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
    // make sure the viewport matches the new window dimensions; note that width and
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}

void mouse_callback(GLFWwindow *window, double xpos, double ypos) {
    if (firstMouse) {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }

    float xoffset = xpos - lastX;
    float yoffset = lastY - ypos; // reversed: y ranges from bottom to top
    lastX = xpos;
    lastY = ypos;

    camera.ProcessMouseMovement(xoffset, yoffset);
    std::cout<<"cameraPos"<<camera.Position.x<<","<<camera.Position.y<<","<<camera.Position.z<<std::endl;
}

void scroll_callback(GLFWwindow *window, double xoffset, double yoffset) {
    camera.ProcessMouseScroll(static_cast<float>(yoffset));
}

我尝试过但不起作用的其他解决方案

此外，如果我只使用镜面反射结果来生成FragColor，结果将如下所示：

在本例中，我的片段着色器是：

#version 330 core
out vec4 FragColor;

in vec3 Normal;
in vec3 FragPos;

uniform vec3 lightPos;
uniform vec3 viewPos;
uniform vec3 lightColor;
uniform vec3 objectColor;

void main()
{
    // ambient
    float ambientStrength = 0.1;
    vec3 ambient = ambientStrength * lightColor;

    // diffuse
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(lightPos - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = diff * lightColor;

    // specular
    float specularStrength = 0.5;
    vec3 viewDir = normalize(viewPos - FragPos);
    float NdotL = dot(norm, lightDir);
    vec3 specular = vec3(0.0);
    if(NdotL > 0.0)
    {
        vec3 reflectDir = reflect(-lightDir, norm);
        float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
        specular = specularStrength * spec * lightColor;
    }

    vec3 result = (ambient + diffuse + specular) * objectColor;

    FragColor = vec4(result, 1.0);
}

上面的代码灵感来自于OpenGL Phong lighting: specular highlight is wrong上的解决方案，但是这个解决方案产生了上面的结果。

opengl

1条答案

按热度按时间
jgovgodb

jgovgodb1#

您没有设置法线向量属性的偏移。法线向量的偏移为3*sizeof(float)
glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float),(void*)0);

glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)(3*sizeof(float)));
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